Accept Python 3 on Windows

[joaocgreis]

This loosely depends on #25878. Doesn't make much sense without it, but doesn't break either.

This allows Python 3 to be used, but only if it is the only Python version installed. #25878 does this for configure, this PR does for vcbuild.

If Python 3 is being used and configure fails, a warning is displayed.

cc @nodejs/platform-windows @nodejs/python @cclauss

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25134/ ✔️

[cclauss]

I am not a Windows guy so patience please...
If I go to the Microsoft Windows Store and install Python from there, where will it go?
My sense is that py is always set to the current preferred Python 3 on Windows boxes. Is that a better way to find py3?

[joaocgreis]

If I go to the Microsoft Windows Store and install Python from there, where will it go?

Under %LocalAppData%\Microsoft\WindowsApps\, which is already in PATH.

My sense is that py is always set to the current preferred Python 3 on Windows boxes. Is that a better way to find py3?

Possibly, but isn't that mostly for people running multiple versions? Is that worth the complexity for our case? For node-gyp that would make more sense I think, if someone has the time to implement it.

Here, we should make sure an installation of Python with all things default works - that's why the PEP514 detection was added: nodejs/CTC#147 (comment). For someone wanting to customize, it's reasonable to assume they can add Python to the path.

[Trott]

@nodejs/python @nodejs/platform-windows @nodejs/build-files This could use some reviews.

It's not clear to me if this should be blocked on #25878 or not. Based on @joaocgreis's comment, I'd say not, but I'd love someone else's opinion (especially @joaocgreis's!).

[cclauss]

What happens on a Windows box when this is run? How far does it get and what are the results? What cannot be achieved by doing python3 configure.py? Our current Python 3.6 runs on Travis Linux run for 50 minutes before timing out. I would be interested to see our builds get to some interesting place before we open the experimentation to a broad audience.

As discussed at #29196 (comment) there are several vectors of testing that I believe we should shape up before opening the floodgates with #25878 and #29236.

1. PYTHON=python3 ; tools/gyp_node.py
2. PYTHON=python3 ; tools/test.py
3. python3 configure.py ; make test # current Travis CI run
4. python3 configure.py ; make install

[cclauss]

Explained at 9m30s into
https://pythonbytes.fm/episodes/show/130/python.exe-now-shipping-with-windows-10

[cclauss]

Given the state of #25789, I think we are ready to land this one.

What are the results of python3.6 configure.py ?

[joaocgreis]

I think this can land. Building with Python 3 does not work, but the error is clear and this allows for experimentation.

@cclauss running configure.py directly on Windows is not straightforward because the environment needs to be set up by vcbuild.bat. FWIW this is what happens:

C:\Users\Administrator\Desktop\node>C:\Users\Administrator\AppData\Local\Programs\Python\Python36\python.exe configure.py
�[1m�[31mERROR�[0m: Did not find a new enough assembler, install one or build with
--openssl-no-asm.
Please refer to BUILDING.md

Running this together with #25878 is a better option, this is what happens:

C:\Users\Administrator\Desktop\node>git checkout nodejs/node/master
...
C:\Users\Administrator\Desktop\node>git clean -fdx
...
C:\Users\Administrator\Desktop\node>git cherry-pick nodejs/node/pull/25878~4..nodejs/node/pull/25878
...
C:\Users\Administrator\Desktop\node>git cherry-pick nodejs/node/pull/29236~2..nodejs/node/pull/29236
...
C:\Users\Administrator\Desktop\node>vcbuild.bat
Looking for Python
Python found in C:\Users\Administrator\AppData\Local\Programs\Python\Python36\\python.exe
WARNING: Python 3 is not yet fully supported, to avoid issues Python 2 should be installed.
Looking for NASM
Looking for Visual Studio 2017
Found MSVS version 15.0
configure --dest-cpu=x64
Node configure: Found Python 3.6.8...
�[1m�[32mINFO�[0m: Using floating patch "tools/icu/patches/64/source/common/putil.cpp" from "tools/icu"
�[1m�[32mINFO�[0m: Using floating patch "tools/icu/patches/64/source/i18n/dtptngen.cpp" from "tools/icu"
Traceback (most recent call last):
File "configure", line 23, in <module>
import configure
File "C:\Users\Administrator\Desktop\node\configure.py", line 1716, in <module>
run_gyp(gyp_args)
File "tools\gyp_node.py", line 54, in run_gyp
rc = gyp.main(args)
File "tools\gyp\pylib\gyp\__init__.py", line 547, in main
return gyp_main(args)
File "tools\gyp\pylib\gyp\__init__.py", line 523, in gyp_main
options.duplicate_basename_check)
File "tools\gyp\pylib\gyp\__init__.py", line 100, in Load
generator = __import__(generator_name, globals(), locals(), generator_name)
File "tools\gyp\pylib\gyp\generator\msvs.py", line 17, in <module>
import gyp.generator.ninja as ninja_generator
File "tools\gyp\pylib\gyp\generator\ninja.py", line 23, in <module>
from cStringIO import StringIO
ModuleNotFoundError: No module named 'cStringIO'
Failed to create vc project files.
Python 3 is not yet fully supported, to avoid issues Python 2 should be installed.
C:\Users\Administrator\Desktop\node>

[cclauss]

Feel free to cherrypick in #29371 if it helps you make progress.

It would be cool if we could set up a Jenkins, Travis CI, or GitHub Actions-based CI, or other CI that exercised Python 3 on Windows.

[bnoordhuis]

My review was requested but I don't think I'm the right person to sign off on this. My Windows shell scripting skills are close to non-existent.

[Trott]

FWIW, since this has been open for more than a week, one approval is enough to land it as long as there isn't any opposition to it (which I'm not seeing any) and CI passes (which it did).

[Trott]

Nit that can totally be ignored, especially since this message eventually will go away anyway.

Suggested change

	echo Python 3 is not yet fully supported, to avoid issues Python 2 should be installed.
	echo Python 3 is not yet fully supported. To avoid issues, Python 2 should be installed.

[Trott]

A bit rubber-stamp-y of me since I don't have a Windows machine available to test on, but LGTM as far as I can tell.

[Trott]

Landed in ab841d5...d18b6a7

[joaocgreis]

@Trott thanks for landing this!