emsdk.ps1 does not find python on Windows

[vanyle]

I am using Windows 11. I have python 3.13.7 installed. I use powershell 7.5.2

λ python --version
Python 3.11.7

I run ./emsdk/emsdk_env.ps1 to activate my environment:

Setting up EMSDK environment (suppress these messages with EMSDK_QUIET=1)
Adding directories to PATH:
PATH += /c/installation_path/of/emsdk
PATH += /c/installation_path/of/emsdk/upstream/emscripten

Setting environment variables:
PATH = ... very long array of paths ...
EMSDK = C:/installation_path/of/emsdk
EMSDK_NODE = C:/installation_path/of/emsdk/node/22.16.0_64bit/bin/node.exe
EMSDK_PYTHON = C:/installation_path/of/emsdk/python/3.13.3_64bit/python.exe

Afterwards, I notice the following:

1. Python is no longer in the PATH

λ python
python: The term 'python' is not recognized as a name of a cmdlet, function, script file, or executable program.
Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

2. The variable "EMSDK_PYTHON" is not defined like the output of the script seems to imply, but "$env:EMSDK_PYTHON" is:

λ echo $EMSDK_PYTHON

λ echo $env:EMSDK_PYTHON
C:/installation_path/of/emsdk/python/3.13.3_64bit/python.exe

3. emsdk.ps1, which uses the $EMSDK_PYTHON variable does not work:

λ .\emsdk\emsdk.ps1 install 4.0.13
Line |
  26 |  & $EMSDK_PY "$ScriptDirectory/emsdk.py" $args
     |    ~~~~~~~~~
     | The term 'python' is not recognized as a name of a cmdlet, function, script file, or executable program. Check the       
     | spelling of the name, or if a path was included, verify that the path is correct and try again.

If I replace occurrences of $EMSDK_PY by $env:EMSDK_PY in this script, the installation of components seems to work again.

However, .\emsdk\emsdk.ps1 activate 4.0.13 does not work in the sense that emcc or em++ are not added to the path.

Is there something wrong with my environment or is the emsdk.ps1 script incorrect?

[sbc100]

It looks like we do have some testing of emsdk.ps1 so I hope its not completely broken. See test/test_activation.ps1 for example.

Looking at emsdk.ps1 itself it looks like EMSDK_PY is supposed to be a local variable that contains the python location, which is different to EMSDK_PYTHON which is a global environment variable which gets set only after activation (emsdk.ps1 needs to be able run before activation).

The fact that the generated ./emsdk/emsdk_env.ps1 somehow removed your system python from the PATH is very odd. Where is the system python located (i.e. what does where python say)?

Also, the PATH += /c/installation_path/of/emsdk looks a little suspicious because it has a mingw/cycwin style path in it. Do you know how / why that might be? Is your system python comign from cywin/mingw maybe? If so that could be the problem. Does he PATH = ... very long array of paths ... path contains cygwin-style or windows-style paths?

[vanyle]

I did some tests and I had both a regular Python 3.13 install and a Python 3.11 from Mingw that gets added to my path by OCaml of all things (opam env).

λ where.exe python
C:\msys64\mingw64\bin\python.exe

Removing the init code of OCaml makes the ./emsdk/emsdk_env.ps1 and the ./emsdk/emsdk.ps1 [activate/install] commands work!

I am surprised that having a mingw python in the path would break everything like that. Also, why do the path look all unixy? While I was using Python on Mingw, I was still on Windows with a Powershell.

The very long array of path contains cygwin-style paths. It is as if the script thinks I am using the bash shell from Mingw.

[sbc100]

I think the reason is that if you run a mingw version of python then emsdk thinks you are running mingw so it does mingw-style things... there may be a way to avoid this be it starts get pretty complicated I think.

[sbc100]

For example if you run the mingw version of python and use os.path.normpath or os.path.abspath I imagine it returns unix-style mingw-friendly paths, right?

[vanyle]

No, Python in Mingw still behaves like regular python on windows, the main difference is that sysconfig.get_platform() indicates that its mingw and paths use slash instead of backslashes when normalized, but they still start with C:/

>>> import os.path
>>> os.path.normpath("C:/path/abc/../def")
'C:/path/def'
>>> import sysconfig
>>> sysconfig.get_platform()
'mingw_x86_64'
>>> os.getenv('MSYSTEM')
'MINGW64'

[sbc100]

I looks like we a bunch of msys specific stuff in emsdk.py. See to_msys_path for example. I assume the version of python you are running is being reported as MSYS?