Not passing environment vars to subprocess

[syrusakbary]

Note: you'll need to use the #4735 PR which unblocks the process.

You can try this by doing:

git clone https://github.com/wasmer-examples/pip-wasmer.git
wasmer-dev run . --net

This will run python -m pip install flask.

And return something similar to:

➜  pip-wasmer wasmer-dev run . --net
Collecting flask
  Downloading flask-3.0.3-py3-none-any.whl.metadata (3.2 kB)
Collecting Werkzeug>=3.0.0 (from flask)
  Downloading werkzeug-3.0.3-py3-none-any.whl.metadata (3.7 kB)
Collecting Jinja2>=3.1.2 (from flask)
  Downloading jinja2-3.1.4-py3-none-any.whl.metadata (2.6 kB)
Collecting itsdangerous>=2.1.2 (from flask)
  Downloading itsdangerous-2.2.0-py3-none-any.whl.metadata (1.9 kB)
Collecting click>=8.1.3 (from flask)
  Downloading click-8.1.7-py3-none-any.whl.metadata (3.0 kB)
Collecting blinker>=1.6.2 (from flask)
  Downloading blinker-1.8.2-py3-none-any.whl.metadata (1.6 kB)
Collecting MarkupSafe>=2.0 (from Jinja2>=3.1.2->flask)
  Downloading MarkupSafe-2.1.5.tar.gz (19 kB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  error: subprocess-exited-with-error

  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [14 lines of output]
      Traceback (most recent call last):
        File "/cpython/lib/python3.12/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
          main()
        File "/cpython/lib/python3.12/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/cpython/lib/python3.12/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 112, in get_requires_for_build_wheel
          backend = _build_backend()
                    ^^^^^^^^^^^^^^^^
        File "/cpython/lib/python3.12/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 74, in _build_backend
          ep = os.environ['PEP517_BUILD_BACKEND']
               ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
        File "<frozen os>", line 685, in __getitem__
      KeyError: 'PEP517_BUILD_BACKEND'
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: subprocess-exited-with-error

× Getting requirements to build wheel did not run successfully.
│ exit code: 1
╰─> See above for output.

note: This error originates from a subprocess, and is likely not a problem with pip.

This is because the environment variables passed in site_packages/pip/_vendor/pyproject_hooks/_impl.py in call_hook:

extra_environ = {'PEP517_BUILD_BACKEND': self.build_backend}

Are not passed properly to the subprocess:

self._subprocess_runner(
   ...,
   extra_environ=extra_environ
)

[syrusakbary]

How to reproduce it minimally:

$ wasmer run python
>>> import subprocess; subprocess.run(["/bin/python"], env={"MY_NEW_VAR": "1"})
(new subprocess):
>>> import os; print(os.environ.get("MY_NEW_VAR"))
None

In native python works properly:

$ python3
>>> import subprocess; subprocess.run(["python3"], env={"MY_NEW_VAR": "1"})
(new subprocess):
>>> import os; print(os.environ.get("MY_NEW_VAR"))
1