bpo-32303 - Consistency fixes for namespace loaders (#5481)

* Make sure ``__spec__.loader`` matches ``__loader__`` for namespace packages.
* Make sure ``__spec__.origin` matches ``__file__`` for namespace packages.

https://bugs.python.org/issue32303
https://bugs.python.org/issue32305

3 files changed, 27 insertions, 6 deletions

diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index 5df6aa0..2bdd192 100644
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -522,6 +522,18 @@ def _init_module_attrs(spec, module, *, override=False):
 
                 loader = _NamespaceLoader.__new__(_NamespaceLoader)
                 loader._path = spec.submodule_search_locations
+                spec.loader = loader
+                # While the docs say that module.__file__ is not set for
+                # built-in modules, and the code below will avoid setting it if
+                # spec.has_location is false, this is incorrect for namespace
+                # packages.  Namespace packages have no location, but their
+                # __spec__.origin is None, and thus their module.__file__
+                # should also be None for consistency.  While a bit of a hack,
+                # this is the best place to ensure this consistency.
+                #
+                # See # https://docs.python.org/3/library/importlib.html#importlib.abc.Loader.load_module
+                # and bpo-32305
+                module.__file__ = None
         try:
             module.__loader__ = loader
         except AttributeError:
diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index d3f58af..f9a708c 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1276,9 +1276,9 @@ class PathFinder:
         elif spec.loader is None:
             namespace_path = spec.submodule_search_locations
             if namespace_path:
-                # We found at least one namespace path.  Return a
-                #  spec which can create the namespace package.
-                spec.origin = 'namespace'
+                # We found at least one namespace path.  Return a spec which
+                # can create the namespace package.
+                spec.origin = None
                 spec.submodule_search_locations = _NamespacePath(fullname, namespace_path, cls._get_spec)
                 return spec
             else:
diff --git a/Lib/importlib/resources.py b/Lib/importlib/resources.py
index bf6d703..c4f6bbd 100644
--- a/Lib/importlib/resources.py
+++ b/Lib/importlib/resources.py
@@ -66,6 +66,11 @@ def _get_resource_reader(
     return None
 
 
+def _check_location(package):
+    if package.__spec__.origin is None or not package.__spec__.has_location:
+        raise FileNotFoundError(f'Package has no location {package!r}')
+
+
 def open_binary(package: Package, resource: Resource) -> BinaryIO:
     """Return a file-like object opened for binary reading of the resource."""
     resource = _normalize_path(resource)
@@ -73,6 +78,7 @@ def open_binary(package: Package, resource: Resource) -> BinaryIO:
     reader = _get_resource_reader(package)
     if reader is not None:
         return reader.open_resource(resource)
+    _check_location(package)
     absolute_package_path = os.path.abspath(package.__spec__.origin)
     package_path = os.path.dirname(absolute_package_path)
     full_path = os.path.join(package_path, resource)
@@ -106,6 +112,7 @@ def open_text(package: Package,
     reader = _get_resource_reader(package)
     if reader is not None:
         return TextIOWrapper(reader.open_resource(resource), encoding, errors)
+    _check_location(package)
     absolute_package_path = os.path.abspath(package.__spec__.origin)
     package_path = os.path.dirname(absolute_package_path)
     full_path = os.path.join(package_path, resource)
@@ -172,6 +179,8 @@ def path(package: Package, resource: Resource) -> Iterator[Path]:
             return
         except FileNotFoundError:
             pass
+    else:
+        _check_location(package)
     # Fall-through for both the lack of resource_path() *and* if
     # resource_path() raises FileNotFoundError.
     package_directory = Path(package.__spec__.origin).parent
@@ -232,9 +241,9 @@ def contents(package: Package) -> Iterator[str]:
         yield from reader.contents()
         return
     # Is the package a namespace package?  By definition, namespace packages
-    # cannot have resources.
-    if (package.__spec__.origin == 'namespace' and
-            not package.__spec__.has_location):
+    # cannot have resources.  We could use _check_location() and catch the
+    # exception, but that's extra work, so just inline the check.
+    if package.__spec__.origin is None or not package.__spec__.has_location:
         return []
     package_directory = Path(package.__spec__.origin).parent
     yield from os.listdir(str(package_directory))