Use custom build backend for PEP 660 editable installs

build_with_distutils_stubs.py

@@ -0,0 +1,70 @@
+"""Generate distutils stub files inside the source directory before packaging.
+We have to do this as a custom build backend for PEP 660 editable installs.
+Doing it this way also allows us to point local type-checkers to types/distutils,
+overriding the stdlib types even on Python < 3.12."""
+
+from __future__ import annotations
+
+import os
+import shutil
+from pathlib import Path
+
+from setuptools._path import StrPath
+from setuptools.build_meta import *  # noqa: F403 # expose everything
+from setuptools.build_meta import (
+    _ConfigSettings,
+    build_editable as _build_editable,
+    build_sdist as _build_sdist,
+    build_wheel as _build_wheel,
+)
+
+_vendored_distutils_path = Path(__file__).parent / "setuptools" / "_distutils"
+_distutils_stubs_path = Path(__file__).parent / "distutils-stubs"
+
+
+def _regenerate_distutils_stubs() -> None:
+    shutil.rmtree(_distutils_stubs_path, ignore_errors=True)
+    _distutils_stubs_path.mkdir(parents=True)
+    (_distutils_stubs_path / ".gitignore").write_text("*")
+    (_distutils_stubs_path / "ruff.toml").write_text('[lint]\nignore = ["F403"]')
+    for path in _vendored_distutils_path.rglob("*.py"):
+        relative_path = path.relative_to(_vendored_distutils_path)
+        if relative_path.parts[0] == "tests":
+            continue
+        # if str(relative_path) == "__init__.py":
+        #     # Work around a mypy issue with types/distutils/__init__.pyi:
+        #     # error: Source file found twice under different module names: "setuptools._distutils.__init__" and "setuptools._distutils"
+        #     (_distutils_stubs_path / "py.typed").write_text('partial')
+        #     continue
+        stub_path = _distutils_stubs_path / relative_path.with_suffix(".pyi")
+        stub_path.parent.mkdir(parents=True, exist_ok=True)
+        module = "setuptools._distutils." + str(relative_path.with_suffix("")).replace(
+            os.sep, "."
+        ).removesuffix(".__init__")
+        stub_path.write_text(f"from {module} import *\n")
+
+
+def build_wheel(  # type: ignore[no-redef]
+    wheel_directory: StrPath,
+    config_settings: _ConfigSettings = None,
+    metadata_directory: StrPath | None = None,
+) -> str:
+    _regenerate_distutils_stubs()
+    return _build_wheel(wheel_directory, config_settings, metadata_directory)
+
+
+def build_sdist(  # type: ignore[no-redef]
+    sdist_directory: StrPath,
+    config_settings: _ConfigSettings = None,
+) -> str:
+    _regenerate_distutils_stubs()
+    return _build_sdist(sdist_directory, config_settings)
+
+
+def build_editable(  # type: ignore[no-redef]
+    wheel_directory: StrPath,
+    config_settings: _ConfigSettings = None,
+    metadata_directory: StrPath | None = None,
+) -> str:
+    _regenerate_distutils_stubs()
+    return _build_editable(wheel_directory, config_settings, metadata_directory)

mypy.ini

@@ -5,7 +5,7 @@
 strict = False
 
 # Early opt-in even when strict = False
-# warn_unused_ignores = True # Disabled as long as there's inconsistent typing issues between pypa and stdlib's distutils
+warn_unused_ignores = True
 warn_redundant_casts = True
 enable_error_code = ignore-without-code
 

pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
 requires = []
-build-backend = "setuptools.build_meta"
+build-backend = "build_with_distutils_stubs"
 backend-path = ["."]
 
 [project]
@@ -202,6 +202,7 @@ include-package-data = true
 include = [
 	"setuptools*",
 	"pkg_resources*",
+	"distutils-stubs*",
 	"_distutils_hack*",
 ]
 exclude = [

setup.py

@@ -3,7 +3,6 @@
 import os
 import sys
 import textwrap
-from pathlib import Path
 
 import setuptools
 from setuptools.command.install import install
@@ -38,22 +37,6 @@ def pypi_link(pkg_filename):
     return '/'.join(parts)
 
 
-vendored_distutils_path = Path(here) / "setuptools" / "_distutils"
-
-
-def generate_distutils_stubs(destination: Path) -> None:
-    for path in vendored_distutils_path.rglob("*.py"):
-        relative_path = path.relative_to(vendored_distutils_path)
-        if relative_path.parts[0] == "tests":
-            continue
-        stub_path = (destination / relative_path).with_suffix(".pyi")
-        stub_path.parent.mkdir(parents=True, exist_ok=True)
-        module = "setuptools._distutils." + str(relative_path.with_suffix("")).replace(
-            os.sep, "."
-        ).removesuffix(".__init__")
-        stub_path.write_text(f"from {module} import *\n")
-
-
 class install_with_pth(install):
     """
     Custom install command to install a .pth file for distutils patching.
@@ -85,10 +68,6 @@ def initialize_options(self):
         install.initialize_options(self)
         self.extra_path = self._pth_name, self._pth_contents
 
-    def run(self):
-        install.run(self)
-        generate_distutils_stubs(Path(self.install_lib) / 'distutils-stubs')
-
     def finalize_options(self):
         install.finalize_options(self)
         self._restore_install_lib()

setuptools/__init__.py

@@ -206,7 +206,7 @@ def ensure_string_list(self, option: str) -> None:
                     f"'{option}' must be a list of strings (got {val!r})"
                 )
 
-    @overload  # type: ignore[override] # extra **kw param that distutils doesn't have
+    @overload
     def reinitialize_command(
         self, command: str, reinit_subcommands: bool = False, **kw
     ) -> _Command: ...

setuptools/command/build_py.py

@@ -48,7 +48,7 @@ def finalize_options(self):
         if 'data_files' in self.__dict__:
             del self.__dict__['data_files']
 
-    def copy_file(  # type: ignore[override] # No overload, no bytes support
+    def copy_file(
         self,
         infile: StrPath,
         outfile: StrPathT,
@@ -135,7 +135,7 @@ def find_data_files(self, package, src_dir):
         )
         return self.exclude_data_files(package, src_dir, files)
 
-    def get_outputs(self, include_bytecode: bool = True) -> list[str]:  # type: ignore[override] # Using a real boolean instead of 0|1
+    def get_outputs(self, include_bytecode: bool = True) -> list[str]:
         """See :class:`setuptools.commands.build.SubCommand`"""
         if self.editable_mode:
             return list(self.get_output_mapping().keys())

setuptools/command/install_lib.py

@@ -95,10 +95,9 @@ def copy_tree(
         self,
         infile: StrPath,
         outfile: str,
-        # override: Using actual booleans
-        preserve_mode: bool = True,  # type: ignore[override]
-        preserve_times: bool = True,  # type: ignore[override]
-        preserve_symlinks: bool = False,  # type: ignore[override]
+        preserve_mode: bool = True,
+        preserve_times: bool = True,
+        preserve_symlinks: bool = False,
         level: object = 1,
     ) -> list[str]:
         assert preserve_mode

setuptools/config/setupcfg.py

@@ -101,7 +101,7 @@ def _apply(
     filenames = [*other_files, filepath]
 
     try:
-        _Distribution.parse_config_files(dist, filenames=filenames)  # type: ignore[arg-type] # Vendored version of distutils supports PathLike
+        _Distribution.parse_config_files(dist, filenames=filenames)
         handlers = parse_configuration(
             dist, dist.command_options, ignore_option_errors=ignore_option_errors
         )

setuptools/dist.py

@@ -727,7 +727,7 @@ def fetch_build_egg(self, req):
 
         return fetch_build_egg(self, req)
 
-    def get_command_class(self, command: str) -> type[distutils.cmd.Command]:  # type: ignore[override] # Not doing complex overrides yet
+    def get_command_class(self, command: str) -> type[distutils.cmd.Command]:
         """Pluggable version of get_command_class()"""
         if command in self.cmdclass:
             return self.cmdclass[command]

setuptools/extension.py

@@ -151,12 +151,7 @@ def __init__(
         # The *args is needed for compatibility as calls may use positional
         # arguments. py_limited_api may be set only via keyword.
         self.py_limited_api = py_limited_api
-        super().__init__(
-            name,
-            sources,  # type: ignore[arg-type] # Vendored version of distutils supports PathLike
-            *args,
-            **kw,
-        )
+        super().__init__(name, sources, *args, **kw)
 
     def _convert_pyx_sources_to_lang(self):
         """

setuptools/modified.py

@@ -1,6 +1,6 @@
 try:
     # Ensure a DistutilsError raised by these methods is the same as distutils.errors.DistutilsError
-    from distutils._modified import (  # type: ignore[import-not-found]
+    from distutils._modified import (
         newer,
         newer_group,
         newer_pairwise,