pants setup_py plugin that reads long description from a file.

setup_plugin.py

class ToolchainSetupKwargsRequest(SetupKwargsRequest):
    @classmethod
    def is_applicable(cls, _: Target) -> bool:
        return True


@rule
async def toolchain_setup_plugin(request: ToolchainSetupKwargsRequest) -> SetupKwargs:
    explicit_kwargs = request.explicit_kwargs
    digest_contents = await Get(
        DigestContents,
        PathGlobs(
            [explicit_kwargs.pop("long_desc_file")],
            description_of_origin="`setup_py()` plugin",
            glob_match_error_behavior=GlobMatchErrorBehavior.error,
        ),
    )
    classifiers = request.explicit_kwargs.pop("additional_classifiers")
    explicit_kwargs.update(
        version=VERSION,
        long_description=digest_contents[0].content.decode(),
        long_description_content_type="text/markdown",
        url="https://toolchain.com",
        license="Proprietary",
        zip_safe=True,
        classifiers=classifiers,
        author="Toolchain Inc",
        author_email="info@toolchain.com",
    )

    return SetupKwargs(explicit_kwargs, address=request.target.address)