gh-124621: Emscripten: Support pyrepl in browser by hoodmane · Pull Request #136931 · python/cpython

hoodmane · 2025-07-21T14:05:00Z

Basic support for pyrepl in Emscripten. Limitations:

requires JSPI
no signal handling implemented

As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling.

Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around.

cc @ambv

Issue: Use new REPL for wasm demo #124621

Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around.

hoodmane · 2025-07-21T14:15:31Z

@adqm If you want to work on any of the followup tasks, let me know. I'm happy to meet / provide suggestions as well if you need them.

hoodmane · 2025-07-21T14:23:13Z

!buildbot emscripten

bedevere-bot · 2025-07-21T14:23:17Z

🤖 New build scheduled with the buildbot fleet by @hoodmane for commit 50c9932 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F136931%2Fmerge

The command will test the builders whose names match following regular expression: emscripten

The builders matched are:

WASM Emscripten PR

hoodmane · 2025-07-21T14:36:18Z

!buildbot emscripten

bedevere-bot · 2025-07-21T14:36:22Z

🤖 New build scheduled with the buildbot fleet by @hoodmane for commit c83eb65 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F136931%2Fmerge

The command will test the builders whose names match following regular expression: emscripten

The builders matched are:

WASM Emscripten PR

hoodmane · 2025-07-21T15:10:13Z

!buildbot emscripten

bedevere-bot · 2025-07-21T15:10:16Z

🤖 New build scheduled with the buildbot fleet by @hoodmane for commit 60e65f5 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F136931%2Fmerge

The command will test the builders whose names match following regular expression: emscripten

The builders matched are:

WASM Emscripten PR

Co-authored-by: Éric <merwok@netwok.org>

miss-islington-app · 2025-07-22T10:13:42Z

Thanks @hoodmane for the PR, and @ambv for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

miss-islington-app · 2025-07-22T10:13:45Z

Sorry, @hoodmane and @ambv, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker c933a6bb329bb97bc7e448388dad1b74f7ca4baa 3.14

Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around. Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: Éric <merwok@netwok.org> (cherry picked from commit c933a6b)

bedevere-app · 2025-07-22T10:30:55Z

GH-136978 is a backport of this pull request to the 3.14 branch.

…GH-136931) Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around. (cherry picked from commit c933a6b) Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com> Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: Éric <merwok@netwok.org>

bedevere-app · 2025-07-22T11:39:14Z

GH-136988 is a backport of this pull request to the 3.14 branch.

If there is an error, we have to return `-errno` not positive errno. Included in backport of pythonGH-136931: python#136988

…H-136988) Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around. (cherry picked from commit c933a6b) Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com> Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: Éric <merwok@netwok.org>

If there is an error, we have to return `-errno` not positive errno. Included in backport of GH-136931: #136988

adqm · 2025-07-23T03:49:15Z

Exciting stuff!

@adqm If you want to work on any of the followup tasks, let me know. I'm happy to meet / provide suggestions as well if you need them.

@hoodmane, I'm certainly happy to help where I can, which is probably more on the web-UI side than on the low-level-details side (though I'd be happy to learn more there, too). If there are particular things you think it would be helpful for me to look at, just let me know; otherwise, I'll poke at the demo and see where to go from there. Happy to coordinate however makes sense for you.

hoodmane · 2025-07-23T08:59:11Z

more on the web-UI side

Help with the UI or anything is very welcome!

Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around. Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: Éric <merwok@netwok.org>

If there is an error, we have to return `-errno` not positive errno. Included in backport of pythonGH-136931: python#136988

Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around. Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: Éric <merwok@netwok.org>

If there is an error, we have to return `-errno` not positive errno. Included in backport of pythonGH-136931: python#136988

…GH-136931) (pythonGH-136988) Basic support for pyrepl in Emscripten. Limitations: * requires JSPI * no signal handling implemented As followup work, it would be nice to implement a webworker variant for when JSPI is not available and proper signal handling. Because it requires JSPI, it doesn't work in Safari. Firefox requires setting an experimental flag. All the Chromiums have full support since May. Until we make it work without JSPI, let's keep the original web_example around. (cherry picked from commit c933a6b) Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com> Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: Éric <merwok@netwok.org>

hoodmane requested review from ambv, corona10, erlend-aasland, freakboy3742, lysnikolaou and pablogsal as code owners July 21, 2025 14:05

bedevere-appBot added the awaiting review label Jul 21, 2025

bedevere-appBot mentioned this pull request Jul 21, 2025
Use new REPL for wasm demo #124621
Closed

hoodmane force-pushed the pyrepl-emscripten branch from 26a2ae2 to 0f6928cCompare July 21, 2025 14:06

hoodmane force-pushed the pyrepl-emscripten branch from 0f6928c to 733846cCompare July 21, 2025 14:08

Add blurb
50c9932

hoodmane added topic-repl Related to the interactive shell OS-emscripten labels Jul 21, 2025

Fix makefile
c83eb65

hoodmane changed the title ~~gh-124621: Emscripten: Support pyrepl~~gh-124621: Emscripten: Support pyrepl in browserJul 21, 2025

ambvand others added 2 commits July 21, 2025 17:05

Be a little petty about color choices
d764db8

Add some extra test skips
60e65f5

Implement FIONBIO using fcntl
79424a4

merwok reviewed Jul 21, 2025
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Comment threadTools/wasm/emscripten/web_example_pyrepl_jspi/index.html

merwok reviewed Jul 21, 2025
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Comment threadTools/wasm/emscripten/web_example_pyrepl_jspi/index.html Outdated

merwok reviewed Jul 21, 2025
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Comment threadTools/wasm/emscripten/web_example_pyrepl_jspi/index.html Outdated

tomasr8 reviewed Jul 21, 2025
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Comment threadModules/posixmodule.c

hoodmaneand others added 2 commits July 22, 2025 11:39

Apply suggestions from code review
d108ea7
Co-authored-by: Éric <merwok@netwok.org>

Merge branch 'main' into pyrepl-emscripten
483c6ec

ambv added the needs backport to 3.14 bugs and security fixes label Jul 22, 2025

ambv merged commit c933a6b into python:mainJul 22, 2025
51 checks passed

bedevere-appBot removed the awaiting review label Jul 22, 2025

miss-islington-appBot assigned ambv Jul 22, 2025

hoodmane deleted the pyrepl-emscripten branch July 22, 2025 10:28

bedevere-appBot removed the needs backport to 3.14 bugs and security fixes label Jul 22, 2025

hoodmane added a commit to hoodmane/cpython that referenced this pull request Jul 22, 2025
pythongh-124621: Emscripten: Fix __syscall_ioctl patch
9dad34c
If there is an error, we have to return `-errno` not positive errno. Included in backport of pythonGH-136931: python#136988

hoodmane mentioned this pull request Jul 22, 2025
gh-124621: Emscripten: Fix __syscall_ioctl patch #136993
Merged

ambv pushed a commit that referenced this pull request Jul 22, 2025
gh-124621: Emscripten: Fix __syscall_ioctl patch (GH-136993)
12d2f37
If there is an error, we have to return `-errno` not positive errno. Included in backport of GH-136931: #136988

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