Handle missing dir skip in dynlib tests

src/venvstacks/_injected/postinstall.py

@@ -100,7 +100,10 @@ def generate_pyvenv_cfg(base_python_path: Path, py_version: str) -> str:
 
 
 def generate_sitecustomize(
-    pylib_paths: Sequence[Path], dynlib_paths: Sequence[Path]
+    pylib_paths: Sequence[Path],
+    dynlib_paths: Sequence[Path],
+    *,
+    skip_missing_dynlib_paths: bool = True,
 ) -> str | None:
     """Generate `sitecustomize.py` contents for given linked environment directories"""
     sc_contents = [_SITE_CUSTOMIZE_HEADER]
@@ -119,10 +122,13 @@ def generate_sitecustomize(
             "from os import add_dll_directory",
         ]
         for dynlib_path in dynlib_paths:
-            if not dynlib_path.exists():
+            if skip_missing_dynlib_paths and not dynlib_path.exists():
                 # Nothing added DLLs to this folder at build time, so skip it
-                continue
-            dynlib_contents.append(f"add_dll_directory({str(dynlib_path)!r})")
+                # (add_dll_directory fails if the specified folder doesn't exist)
+                dynlib_entry = f"# Skipping {str(dynlib_path)!r} (no such directory)"
+            else:
+                dynlib_entry = f"add_dll_directory({str(dynlib_path)!r})"
+            dynlib_contents.append(dynlib_entry)
         dynlib_contents.append("")
         sc_contents.extend(dynlib_contents)
     if len(sc_contents) == 1:

tests/test_postinstall.py

@@ -47,19 +47,46 @@ def _make_dynlib_paths() -> tuple[list[Path], str]:
     return dynlib_paths, expected_lines
 
 
+def _make_missing_dynlib_paths() -> tuple[list[Path], str]:
+    dynlib_dirs = [f"dynlib{n}" for n in range(5)]
+    dynlib_paths = [Path(d) for d in dynlib_dirs]
+    expected_lines = "\n".join(
+        f"# Skipping {d!r} (no such directory)" for d in dynlib_dirs
+    )
+    return dynlib_paths, expected_lines
+
+
 def test_sitecustomize() -> None:
     pylib_paths, expected_lines = _make_pylib_paths()
     sc_text = postinstall.generate_sitecustomize(pylib_paths, [])
     assert sc_text is not None
     assert sc_text.startswith(postinstall._SITE_CUSTOMIZE_HEADER)
     assert expected_lines in sc_text
     assert "add_dll_directory(" not in sc_text
+    assert "# Skipping" not in sc_text
     assert compile(sc_text, "_sitecustomize.py", "exec") is not None
 
 
 def test_sitecustomize_with_dynlib() -> None:
     pylib_paths, expected_pylib_lines = _make_pylib_paths()
     dynlib_paths, expected_dynlib_lines = _make_dynlib_paths()
+    sc_text = postinstall.generate_sitecustomize(
+        pylib_paths, dynlib_paths, skip_missing_dynlib_paths=False
+    )
+    assert sc_text is not None
+    assert sc_text.startswith(postinstall._SITE_CUSTOMIZE_HEADER)
+    assert expected_pylib_lines in sc_text
+    if hasattr(os, "add_dll_directory"):
+        assert expected_dynlib_lines in sc_text
+    else:
+        assert "add_dll_directory(" not in sc_text
+        assert "# Skipping" not in sc_text
+    assert compile(sc_text, "_sitecustomize.py", "exec") is not None
+
+
+def test_sitecustomize_with_missing_dynlib() -> None:
+    pylib_paths, expected_pylib_lines = _make_pylib_paths()
+    dynlib_paths, expected_dynlib_lines = _make_missing_dynlib_paths()
     sc_text = postinstall.generate_sitecustomize(pylib_paths, dynlib_paths)
     assert sc_text is not None
     assert sc_text.startswith(postinstall._SITE_CUSTOMIZE_HEADER)
@@ -68,4 +95,5 @@ def test_sitecustomize_with_dynlib() -> None:
         assert expected_dynlib_lines in sc_text
     else:
         assert "add_dll_directory(" not in sc_text
+        assert "# Skipping" not in sc_text
     assert compile(sc_text, "_sitecustomize.py", "exec") is not None