Add new tool.pdm field for editable dependencies

[agoose77]

Is your feature request related to a problem? Please describe.

Right now PDM supports the specification of editable dependencies with an -e prefix. This is useful, but means that the resulting pyproject.toml file is no longer PEP 508 compliant. If you use a different build backend e.g. hatch, it will fail because of this incompatibility. Besides build backends, there are a myriad of other tools that could try to read this section.

$ pyproject-build -w
* Creating venv isolated environment...
* Installing packages in isolated environment... (hatchling)
* Getting dependencies for wheel...
* Building wheel...
Traceback (most recent call last):
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/packaging/requirements.py", line 102, in __init__
    req = REQUIREMENT.parseString(requirement_string)
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/pyparsing/core.py", line 1141, in parse_string
    raise exc.with_traceback(None)
pyparsing.exceptions.ParseException: Expected W:(0-9A-Za-z), found '-'  (at char 0), (line:1, col:1)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/hatchling/metadata/core.py", line 997, in dependencies_complex
    requirement = Requirement(entry)
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/packaging/requirements.py", line 104, in __init__
    raise InvalidRequirement(
packaging.requirements.InvalidRequirement: Parse error at "'-e file:'": Expected W:(0-9A-Za-z)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/angus/.local/pipx/venvs/build/lib/python3.10/site-packages/pep517/in_process/_in_process.py", line 363, in <module>
    main()
  File "/home/angus/.local/pipx/venvs/build/lib/python3.10/site-packages/pep517/in_process/_in_process.py", line 345, in main
    json_out['return_val'] = hook(**hook_input['kwargs'])
  File "/home/angus/.local/pipx/venvs/build/lib/python3.10/site-packages/pep517/in_process/_in_process.py", line 261, in build_wheel
    return _build_backend().build_wheel(wheel_directory, config_settings,
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/hatchling/build.py", line 41, in build_wheel
    return os.path.basename(next(builder.build(wheel_directory, ['standard'])))
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/hatchling/builders/plugin/interface.py", line 77, in build
    self.metadata.core.validate_fields()
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/hatchling/metadata/core.py", line 1119, in validate_fields
    getattr(self, attribute)
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/hatchling/metadata/core.py", line 1018, in dependencies
    self._dependencies = sorted(self.dependencies_complex)
  File "/tmp/build-env-7c0nfg0j/lib/python3.10/site-packages/hatchling/metadata/core.py", line 999, in dependencies_complex
    raise ValueError('Dependency #{} of field `project.dependencies` is invalid: {}'.format(i, e))
ValueError: Dependency #1 of field `project.dependencies` is invalid: Parse error at "'-e file:'": Expected W:(0-9A-Za-z)

ERROR Backend subproccess exited when trying to invoke build_wheel

Describe the solution you'd like

Remove this "extra" syntax, and add a new tool.pdm field to enumerate the editable packages.

By adding PDM-only metadata to indicate that these are editable packages, we can avoid breaking other tools. At the moment, editable packages are an implementation detail rather than something described by a packaging standard. This would mean that e.g. other build backends would end up using the non-editable version of the package. This seems to me to be the only good option unless a new

[project]
dependencies = [
    "my-local-package>=1.0.0"
]
[tool.pdm]
editable = [
    "my-local-package"
]

I'm sorry that I'm not submitting a PR alongside this. Right now, I just don't have any time to work on OS. I thought I'd create this issue as a TODO-item :)

[frostming]

Hi, I am going to forbid adding editable packages to the [project] table, but they are still allowed in the dev-dependencies table.

This will be a breaking change so I will make it in PDM 2.0, thanks.

[frostming]

Closed by #1140, please test it on 2.0.0a1