Fix editable install finder handling of nested packages (#4020)

docs/conf.py

@@ -232,7 +232,7 @@
 html_static_path = ['images']  # should contain the folder with icons
 
 # Add support for nice Not Found 404 pages
-extensions += ['notfound.extension']
+# extensions += ['notfound.extension']  # readthedocs/sphinx-notfound-page#219
 
 # List of dicts with <link> HTML attributes
 # static-file points to files in the html_static_path (href is computed)

newsfragments/4020.bugfix.rst

@@ -0,0 +1,3 @@
+Fix editable install finder handling of nested packages, by only handling 1
+level of nesting and relying on ``importlib.machinery`` to find the remaining
+modules based on the parent package path.

setup.cfg

@@ -92,7 +92,7 @@ testing-integration =
 
 docs =
 	# upstream
-	sphinx >= 3.5
+	sphinx >= 3.5,<=7.1.2  # workaround, see comments in pypa/setuptools#4020
 	jaraco.packaging >= 9.3
 	rst.linker >= 1.9
 	furo

setuptools/command/editable_wheel.py

@@ -782,11 +782,15 @@ def find_spec(cls, fullname, path=None, target=None):
             pkg_path = MAPPING[fullname]
             return cls._find_spec(fullname, Path(pkg_path))
 
-        # Nested modules (apparently required for namespaces to work)
-        for pkg, pkg_path in reversed(list(MAPPING.items())):
-            if fullname.startswith(f"{{pkg}}."):
-                return cls._find_nested_spec(fullname, pkg, pkg_path)
-
+        # Handle immediate children modules (required for namespaces to work)
+        # To avoid problems with case sensitivity in the file system we delegate
+        # to the importlib.machinery implementation.
+        parent, _, child = fullname.rpartition(".")
+        if parent and parent in MAPPING:
+            return PathFinder.find_spec(fullname, path=[MAPPING[parent]])
+
+        # Other levels of nesting should be handled automatically by importlib
+        # using the parent path.
         return None
 
     @classmethod
@@ -797,20 +801,6 @@ def _find_spec(cls, fullname, candidate_path):
             if candidate.exists():
                 return spec_from_file_location(fullname, candidate)
 
-    @classmethod
-    def _find_nested_spec(cls, fullname, parent, parent_path):
-        '''
-        To avoid problems with case sensitivity in the file system we delegate to the
-        importlib.machinery implementation.
-        '''
-        rest = fullname.replace(parent, "", 1).strip(".")
-        nested = PathFinder.find_spec(rest, path=[parent_path])
-        return nested and spec_from_file_location(
-            fullname,
-            nested.origin,
-            submodule_search_locations=nested.submodule_search_locations
-        )
-
 
 class _EditableNamespaceFinder:  # PathEntryFinder
     @classmethod

setuptools/tests/test_editable_install.py

@@ -660,6 +660,50 @@ def test_namespace_case_sensitivity(self, tmp_path):
             with pytest.raises(ImportError, match="\'ns\\.othername\\.foo\\.BAR\\'"):
                 import_module("ns.othername.foo.BAR")
 
+    def test_intermediate_packages(self, tmp_path):
+        """
+        The finder should not import ``fullname`` if the intermediate segments
+        don't exist (see pypa/setuptools#4019).
+        """
+        files = {
+            "src": {
+                "mypkg": {
+                    "__init__.py": "",
+                    "config.py": "a = 13",
+                    "helloworld.py": "b = 13",
+                    "components": {
+                        "config.py": "a = 37",
+                    },
+                },
+            }
+        }
+        jaraco.path.build(files, prefix=tmp_path)
+
+        mapping = {"mypkg": str(tmp_path / "src/mypkg")}
+        template = _finder_template(str(uuid4()), mapping, {})
+
+        with contexts.save_paths(), contexts.save_sys_modules():
+            for mod in (
+                "mypkg",
+                "mypkg.config",
+                "mypkg.helloworld",
+                "mypkg.components",
+                "mypkg.components.config",
+                "mypkg.components.helloworld",
+            ):
+                sys.modules.pop(mod, None)
+
+            self.install_finder(template)
+
+            config = import_module("mypkg.components.config")
+            assert config.a == 37
+
+            helloworld = import_module("mypkg.helloworld")
+            assert helloworld.b == 13
+
+            with pytest.raises(ImportError):
+                import_module("mypkg.components.helloworld")
+
 
 def test_pkg_roots(tmp_path):
     """This test focus in getting a particular implementation detail right.