feat: Support main_module with bootstrap_impl=system_python#3072

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feat: Support main_module with bootstrap_impl=system_python #3072

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ef12d0a
test: Add test for main_module with bootstrap_impl=system_python
brandonchinn178 Jul 11, 2025
e87d7e8
feat: Support main_module with bootstrap_impl=system_python
brandonchinn178 Jul 11, 2025
418a70c
Address feedback
brandonchinn178 Jul 11, 2025
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1 change: 1 addition & 0 deletions CHANGELOG.md
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
* 3.12.11
* 3.13.5
* 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down
2 changes: 1 addition & 1 deletion CONTRIBUTING.md
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down
9 changes: 9 additions & 0 deletions python/private/main_module_entrypoint_template.py
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Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.

@rickeylevrickeylevJul 10, 2025

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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.

@brandonchinn178brandonchinn178Jul 10, 2025

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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"

@brandonchinn178brandonchinn178Jul 11, 2025

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yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact

"""

import os
import runpy

if __name__ == "__main__":
runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)
40 changes: 33 additions & 7 deletions python/private/py_executable.bzl
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
# empty target for other platforms.
default = "//tools/launcher:launcher",
),
"_main_module_entrypoint_template": lambda: attrb.Label(
allow_single_file = True,
default = "//python/private:main_module_entrypoint_template.py",
),
"_py_interpreter": lambda: attrb.Label(
# The configuration_field args are validated when called;
# we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
)
else:
stage2_bootstrap = None
extra_runfiles = ctx.runfiles()
zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
_create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
ctx,
output = zip_main,
main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
if bootstrap_output != None:
fail("Should not occur: bootstrap_output should not be used " +
"when creating an executable zip")
_create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
ctx,
output = executable,
zip_file = zip_file,
stage2_bootstrap = stage2_bootstrap,
runtime_details = runtime_details,
venv = venv,
)
extra_runfiles = extra_runfiles.merge(more_runfiles)
elif bootstrap_output:
_create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
ctx,
output = bootstrap_output,
stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
main_py = main_py,
venv = venv,
)
extra_runfiles = extra_runfiles.merge(more_runfiles)
else:
# Otherwise, this should be the Windows case of launcher + zip.
# Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
is_for_zip,
runtime_details,
venv = None):
extra_runfiles = ctx.runfiles()
runtime = runtime_details.effective_runtime

if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
)
template = runtime.bootstrap_template
subs["%shebang%"] = runtime.stub_shebang
elif not ctx.files.srcs:
fail("mandatory 'srcs' files have not been provided")
else:
if not ctx.files.srcs and not ctx.attr.main_module:
fail("mandatory 'srcs' files have not been provided")

if (ctx.configuration.coverage_enabled and
runtime and
runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
subs["%coverage_tool%"] = coverage_tool_runfiles_path
subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
subs["%imports%"] = ":".join(imports.to_list())

if ctx.attr.main_module:
main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
ctx.actions.expand_template(
template = ctx.file._main_module_entrypoint_template,
output = main_module_entrypoint,
substitutions = {"%main_module%": ctx.attr.main_module},
)
main_py = main_module_entrypoint
extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
elif not main_py:
# shouldn't happen
fail("Neither main nor main_module was provided")

subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
substitutions = subs,
)

return extra_runfiles

def _create_windows_exe_launcher(
ctx,
*,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
sibling = output,
)
if stage2_bootstrap:
_create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
ctx,
output = prelude,
stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
venv = venv,
)
else:
extra_runfiles = ctx.runfiles()
ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
progress_message = "Build Python zip executable: %{label}",
)

return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
return create_cc_details_struct(
Expand Down
4 changes: 2 additions & 2 deletions tests/base_rules/py_executable_base_tests.bzl
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
)

def _test_main_module_bootstrap_system_python_impl(env, target):
env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
)

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down
19 changes: 16 additions & 3 deletions tests/bootstrap_impls/BUILD.bazel
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
main = "sys_path_order_test.py",
)

py_reconfig_test(
name = "main_module_test",
py_library(
name = "main_module_lib",
srcs = ["main_module.py"],
bootstrap_impl = "script",
imports = ["."],

@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting

@brandonchinn178brandonchinn178Jul 11, 2025

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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?

)

py_reconfig_test(
name = "main_module_script_test",
bootstrap_impl = "script",
main_module = "tests.bootstrap_impls.main_module",
target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
deps = [":main_module_lib"],
)

py_reconfig_test(
name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.
bootstrap_impl = "system_python",
main_module = "tests.bootstrap_impls.main_module",
deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
feat: Support main_module with bootstrap_impl=system_python#3072

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3
commits into

base:main
Choose a base branch

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 Open


feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

Address feedback


brandonchinn178 Jul 11, 2025

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1 change: 1 addition & 0 deletions
CHANGELOG.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

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Collaborator
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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

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ContributorAuthor
Choose a reason for hiding this comment

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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

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ContributorAuthor
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yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
)

py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.

 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
feat: Support main_module with bootstrap_impl=system_python#3072

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

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 Open

brandonchinn178
wants to merge
3
commits into

base:main
Choose a base branch

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feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

Address feedback


brandonchinn178 Jul 11, 2025

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1 change: 1 addition & 0 deletions
CHANGELOG.md

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Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

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yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
)

py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.

 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

Address feedback


brandonchinn178 Jul 11, 2025

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1 change: 1 addition & 0 deletions
CHANGELOG.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

Copy link


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ContributorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

Copy link


Copy Markdown

ContributorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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ContributorAuthor
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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
)

py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.

 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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feat: Support main_module with bootstrap_impl=system_python#3072

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feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

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brandonchinn178 Jul 11, 2025

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1 change: 1 addition & 0 deletions
CHANGELOG.md

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Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

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yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
)

py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.

 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
feat: Support main_module with bootstrap_impl=system_python#3072

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commits into

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Choose a base branch

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feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

Address feedback


brandonchinn178 Jul 11, 2025

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1 change: 1 addition & 0 deletions
CHANGELOG.md

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

Copy link


Copy Markdown

Collaborator
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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

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ContributorAuthor
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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

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ContributorAuthor
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yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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ContributorAuthor
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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
)

py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.

 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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feat: Support main_module with bootstrap_impl=system_python#3072

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feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

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1 change: 1 addition & 0 deletions
CHANGELOG.md

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Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

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yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
)

py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
Comment thread
brandonchinn178 marked this conversation as resolved.

 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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feat: Support main_module with bootstrap_impl=system_python#3072

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 Open

brandonchinn178
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commits into

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Choose a base branch

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feat: Support main_module with bootstrap_impl=system_python
#3072
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ef12d0a

test: Add test for main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
e87d7e8

feat: Support main_module with bootstrap_impl=system_python


brandonchinn178 Jul 11, 2025
418a70c

Address feedback


brandonchinn178 Jul 11, 2025

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1 change: 1 addition & 0 deletions
CHANGELOG.md

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Original file line numberDiff line numberDiff line change
Expand Up@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 * 3.12.11
 * 3.13.5
 * 3.14.0b3
* (rules) {obj}`main_module` now works without needing to set {obj}`--bootstrap_impl=script`

{#v0-0-0-removed}
### Removed
Expand Down

2 changes: 1 addition & 1 deletion
CONTRIBUTING.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -122,7 +122,7 @@ the [Breaking Changes](#breaking-changes) section for how to introduce breaking
changes.

User visible changes, such as features, fixes, or notable refactors, should
be documneted in CHANGELOG.md and their respective API doc. See [Documenting
be documented in CHANGELOG.md and their respective API doc. See [Documenting
changes] for how to do so.

Common `type`s:
Expand Down

9 changes: 9 additions & 0 deletions
python/private/main_module_entrypoint_template.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
"""
A shim to get `main_module` working with `bootstrap_impl=system_python`.
@rickeylevrickeylevJul 10, 2025

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Collaborator
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Instead of creating a shim like this, modify the bootstrap template. All it should really need is to populate a %main_module% variable and pass -m when invoking python. That should simplify things quite a bit.
@brandonchinn178brandonchinn178Jul 10, 2025

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ContributorAuthor
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hm I could try it again, but it was difficult because then I'd have to update all the locations where %main% is used, since there isn't a main file anymore. It seemed easier to say "we're using the main file logic everywhere still, it just points to a shim"
@brandonchinn178brandonchinn178Jul 11, 2025

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ContributorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

yeah, it seems like the notion of a main file is hardcoded in a lot of places in python_bootstrap_template.txt. It's also not immediately clear how the translation to -m <main_module> would work for the coverage path. The shim seems like the easiest solution, especially given this is a deprecated codepath and it should have a negligible performance impact
"""

import os
import runpy

if __name__ == "__main__":
 runpy.run_module("%main_module%", run_name="__main__", alter_sys=True)

40 changes: 33 additions & 7 deletions
python/private/py_executable.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -201,6 +201,10 @@ accepting arbitrary Python versions.
 # empty target for other platforms.
 default = "//tools/launcher:launcher",
 ),
 "_main_module_entrypoint_template": lambda: attrb.Label(
 allow_single_file = True,
 default = "//python/private:main_module_entrypoint_template.py",
 ),
 "_py_interpreter": lambda: attrb.Label(
 # The configuration_field args are validated when called;
 # we use the precense of py_internal to indicate this Bazel
Expand DownExpand Up@@ -360,9 +364,8 @@ def _create_executable(
 )
 else:
 stage2_bootstrap = None
 extra_runfiles = ctx.runfiles()
 zip_main = ctx.actions.declare_file(base_executable_name + ".temp", sibling = executable)
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = zip_main,
 main_py = main_py,
Expand DownExpand Up@@ -426,16 +429,17 @@ def _create_executable(
 if bootstrap_output != None:
 fail("Should not occur: bootstrap_output should not be used " +
 "when creating an executable zip")
 _create_executable_zip_file(
more_runfiles = _create_executable_zip_file(
 ctx,
 output = executable,
 zip_file = zip_file,
 stage2_bootstrap = stage2_bootstrap,
 runtime_details = runtime_details,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 elif bootstrap_output:
 _create_stage1_bootstrap(
more_runfiles = _create_stage1_bootstrap(
 ctx,
 output = bootstrap_output,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -445,6 +449,7 @@ def _create_executable(
 main_py = main_py,
 venv = venv,
 )
 extra_runfiles = extra_runfiles.merge(more_runfiles)
 else:
 # Otherwise, this should be the Windows case of launcher + zip.
 # Double check this just to make sure.
Expand DownExpand Up@@ -796,6 +801,7 @@ def _create_stage1_bootstrap(
 is_for_zip,
 runtime_details,
 venv = None):
 extra_runfiles = ctx.runfiles()
 runtime = runtime_details.effective_runtime

 if venv:
Expand DownExpand Up@@ -833,9 +839,10 @@ def _create_stage1_bootstrap(
 )
 template = runtime.bootstrap_template
 subs["%shebang%"] = runtime.stub_shebang
 elif not ctx.files.srcs:
 fail("mandatory 'srcs' files have not been provided")
 else:
 if not ctx.files.srcs and not ctx.attr.main_module:
 fail("mandatory 'srcs' files have not been provided")

 if (ctx.configuration.coverage_enabled and
 runtime and
 runtime.coverage_tool):
Expand All@@ -855,6 +862,20 @@ def _create_stage1_bootstrap(
 subs["%coverage_tool%"] = coverage_tool_runfiles_path
 subs["%import_all%"] = ("True" if ctx.fragments.bazel_py.python_import_all_repositories else "False")
 subs["%imports%"] = ":".join(imports.to_list())

 if ctx.attr.main_module:
 main_module_entrypoint = ctx.actions.declare_file("main_module_entrypoint.py")
 ctx.actions.expand_template(
 template = ctx.file._main_module_entrypoint_template,
 output = main_module_entrypoint,
 substitutions = {"%main_module%": ctx.attr.main_module},
 )
 main_py = main_module_entrypoint
 extra_runfiles = extra_runfiles.merge(ctx.runfiles([main_module_entrypoint]))
 elif not main_py:
 # shouldn't happen
 fail("Neither main nor main_module was provided")

 subs["%main%"] = "{}/{}".format(ctx.workspace_name, main_py.short_path)

 ctx.actions.expand_template(
Expand All@@ -863,6 +884,8 @@ def _create_stage1_bootstrap(
 substitutions = subs,
 )

 return extra_runfiles

def _create_windows_exe_launcher(
 ctx,
 *,
Expand DownExpand Up@@ -985,7 +1008,7 @@ def _create_executable_zip_file(
 sibling = output,
 )
 if stage2_bootstrap:
 _create_stage1_bootstrap(
extra_runfiles = _create_stage1_bootstrap(
 ctx,
 output = prelude,
 stage2_bootstrap = stage2_bootstrap,
Expand All@@ -994,6 +1017,7 @@ def _create_executable_zip_file(
 venv = venv,
 )
 else:
 extra_runfiles = ctx.runfiles()
 ctx.actions.write(prelude, "#!/usr/bin/env python3\n")

 ctx.actions.run_shell(
Expand All@@ -1009,6 +1033,8 @@ def _create_executable_zip_file(
 progress_message = "Build Python zip executable: %{label}",
 )

 return extra_runfiles

def _get_cc_details_for_binary(ctx, extra_deps):
 cc_info = collect_cc_info(ctx, extra_deps = extra_deps)
 return create_cc_details_struct(
Expand Down

4 changes: 2 additions & 2 deletions
tests/base_rules/py_executable_base_tests.bzl

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -363,8 +363,8 @@ def _test_main_module_bootstrap_system_python(name, config):
 )

def _test_main_module_bootstrap_system_python_impl(env, target):
 env.expect.that_target(target).failures().contains_predicate(
matching.str_matches("mandatory*srcs"),
 env.expect.that_target(target).default_outputs().contains(
"{package}/{test_name}_subject",
 )

_tests.append(_test_main_module_bootstrap_system_python)
Expand Down

19 changes: 16 additions & 3 deletions
tests/bootstrap_impls/BUILD.bazel

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
# limitations under the License.
load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_shell//shell:sh_test.bzl", "sh_test")
load("//python:defs.bzl", "py_library")
load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
Expand DownExpand Up@@ -123,13 +124,25 @@ py_reconfig_test(
 main = "sys_path_order_test.py",
)

py_reconfig_test(
 name = "main_module_test",
py_library(
 name = "main_module_lib",
 srcs = ["main_module.py"],
 bootstrap_impl = "script",
 imports = ["."],
@rickeylevrickeylevJul 10, 2025

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This needs to be kept because it ensures the correct entry is added to sys.path. Without it, it can inadvertently rely on the implicit behavior from the flag that adds repos to sys.path and the PYTHONSAFEPATH setting
@brandonchinn178brandonchinn178Jul 11, 2025

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I can re-add it, but I don't understand the reasoning. IIUC, imports says "add this directory to PYTHONPATH", but we're specifying main_module with the full absolute path, so imports = ["."] isn't doing anything. Would imports = [] have the behavior you want?
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py_reconfig_test(
 name = "main_module_script_test",
 bootstrap_impl = "script",
 main_module = "tests.bootstrap_impls.main_module",
 target_compatible_with = SUPPORTS_BOOTSTRAP_SCRIPT,
 deps = [":main_module_lib"],
)

py_reconfig_test(
 name = "main_module_system_python_test",
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 bootstrap_impl = "system_python",
 main_module = "tests.bootstrap_impls.main_module",
 deps = [":main_module_lib"],
)

sh_py_run_test(
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