PEP 517 builds cannot resolve directory dependencies

[AndrewGuenther]

pip version

21.0.1

Python version

3.8.5

OS

Linux, Ubuntu 20.04

Additional information

Relevant pyproject.toml bits:

[build-system]
requires = ["poetry-core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

Poetry is an illustrative example here, but the root cause lies within pip (or possibly even PEP 517)

Description

When performing a PEP 517 build, pip creates an isolated environment for the build to execute in within a temporary directory. No information about the directory the build originated from is shared with the build backend. As a result, any dependencies specified as a relative file/folder path cannot be resolved.

Expected behavior

Relative directory dependencies can be resolved in a PEP 517 build

How to Reproduce

1. Create a project which specifies a relative directory dependency using a PEP 517 build backend
2. Run pip install .
3. Build will fail to resolve directory dependency

Output

Most of this output is from poetry, but including here for completeness

Processing /home/andrew/worksapce/projects/my-project
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... error
    ERROR: Command errored out with exit status 1:
     command: /home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/bin/python /home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py prepare_metadata_for_build_wheel /tmp/tmp0h3jkq4v
         cwd: /tmp/pip-req-build-5e4zvq59
    Complete output (16 lines):
    Traceback (most recent call last):
      File "/home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py", line 280, in <module>
        main()
      File "/home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py", line 263, in main
        json_out['return_val'] = hook(**hook_input['kwargs'])
      File "/home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py", line 133, in prepare_metadata_for_build_wheel
        return hook(metadata_directory, config_settings)
      File "/tmp/pip-build-env-ta34h747/overlay/lib/python3.8/site-packages/poetry/core/masonry/api.py", line 43, in prepare_metadata_for_build_wheel
        poetry = Factory().create_poetry(Path(".").resolve(), with_dev=False)
      File "/tmp/pip-build-env-ta34h747/overlay/lib/python3.8/site-packages/poetry/core/factory.py", line 93, in create_poetry
        self.create_dependency(name, constraint, root_dir=package.root_dir)
      File "/tmp/pip-build-env-ta34h747/overlay/lib/python3.8/site-packages/poetry/core/factory.py", line 244, in create_dependency
        dependency = DirectoryDependency(
      File "/tmp/pip-build-env-ta34h747/overlay/lib/python3.8/site-packages/poetry/core/packages/directory_dependency.py", line 41, in __init__
        raise ValueError("Directory {} does not exist".format(self._path))
    ValueError: Directory ../../lib/my-project-lib does not exist
    ----------------------------------------
WARNING: Discarding file:///home/andrew/worksapce/projects/my-project. Command errored out with exit status 1: /home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/bin/python /home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py prepare_metadata_for_build_wheel /tmp/tmp0h3jkq4v Check the logs for full command output.
ERROR: Command errored out with exit status 1: /home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/bin/python /home/andrew/.cache/pypoetry/virtualenvs/my-project-JuauOX3v-py3.8/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py prepare_metadata_for_build_wheel /tmp/tmp0h3jkq4v Check the logs for full command output.

Code of Conduct

• I agree to follow the PSF Code of Conduct

[uranusjr]

Relative paths in a package is a non-standard Poetry extension. The build is handled by Poetry, so it should either reject this with a clear message, or somehow support it for you. pip can't do much about this.