Explicitly define the build/lib* paths

src/poetry/core/masonry/builders/wheel.py

@@ -9,6 +9,7 @@
 import stat
 import subprocess
 import sys
+import sysconfig
 import tempfile
 import zipfile
 
@@ -187,16 +188,13 @@ def _build(self, wheel: zipfile.ZipFile) -> None:
                         # in-place - so there's no need to copy them into the zip
                         return
 
-                    build_dir = self._path / "build"
-                    libs: list[Path] = list(build_dir.glob("lib.*"))
-                    if not libs:
+                    lib = self._get_build_lib_dir()
+                    if lib is None:
                         # The result of building the extensions
                         # does not exist, this may due to conditional
                         # builds, so we assume that it's okay
                         return
 
-                    lib = libs[0]
-
                     for pkg in sorted(lib.glob("**/*")):
                         if pkg.is_dir() or self.is_excluded(pkg):
                             continue
@@ -210,6 +208,25 @@ def _build(self, wheel: zipfile.ZipFile) -> None:
 
                         self._add_file(wheel, pkg, rel_path)
 
+    def _get_build_purelib_dir(self) -> Path:
+        return self._path / "build/lib"
+
+    def _get_build_platlib_dir(self) -> Path:
+        # Roughly equivalent to the naming convention in used by distutils, see:
+        # distutils.command.build.build.finalize_options
+        plat_specifier = f"{sysconfig.get_platform()}-{sys.implementation.cache_tag}"
+        return self._path / f"build/lib.{plat_specifier}"
+
+    def _get_build_lib_dir(self) -> Path | None:
+        # Either the purelib or platlib path will have been used when building
+        build_platlib = self._get_build_platlib_dir()
+        build_purelib = self._get_build_purelib_dir()
+        if build_platlib.exists():
+            return build_platlib
+        elif build_purelib.exists():
+            return build_purelib
+        return None
+
     def _copy_file_scripts(self, wheel: zipfile.ZipFile) -> None:
         file_scripts = self.convert_script_files()
 
@@ -237,6 +254,10 @@ def _run_build_command(self, setup: Path) -> None:
                 "build",
                 "-b",
                 str(self._path / "build"),
+                "--build-purelib",
+                str(self._get_build_purelib_dir()),
+                "--build-platlib",
+                str(self._get_build_platlib_dir()),
             ]
         )
 

tests/masonry/builders/fixtures/build_with_build_py_only/README.rst

@@ -0,0 +1,2 @@
+Module 1
+========

tests/masonry/builders/fixtures/build_with_build_py_only/build.py

@@ -0,0 +1,15 @@
+from pathlib import Path
+from setuptools.command.build_py import build_py
+
+
+class BuildPyCommand(build_py):
+    def run(self):
+        gen_file = Path("build_with_build_py_only/generated/file.py")
+        gen_file.touch()
+        ret = super().run()
+        gen_file.unlink()
+        return ret
+
+
+def build(setup_kwargs):
+    setup_kwargs["cmdclass"] = {"build_py": BuildPyCommand}

tests/masonry/builders/fixtures/build_with_build_py_only/pyproject.toml

@@ -0,0 +1,16 @@
+[tool.poetry]
+name = "build_with_build_py_only"
+version = "0.1"
+description = "Some description."
+authors = [
+    "Robert Belter <[email protected]>"
+]
+license = "MIT"
+
+readme = "README.rst"
+
+homepage = "https://python-poetry.org/"
+
+[tool.poetry.build]
+script = "build.py"
+generate-setup-file = true

tests/masonry/builders/test_wheel.py

@@ -417,3 +417,18 @@ def test_extended_editable_build_inplace() -> None:
     assert any(
         (root / "extended" / f"extended{ext}").exists() for ext in shared_lib_extensions
     )
+
+
+def test_build_py_only_included() -> None:
+    """Tests that a build.py that only defined the command build_py (which generates a
+    lib folder) will have its artifacts included.
+    """
+    root = fixtures_dir / "build_with_build_py_only"
+    WheelBuilder.make(Factory().create_poetry(root))
+
+    whl = next((root / "dist").glob("build_with_build_py_only-0.1-*.whl"))
+
+    assert whl.exists()
+
+    with zipfile.ZipFile(str(whl)) as z:
+        assert "build_with_build_py_only/generated/file.py" in z.namelist()