autodoc: only mock specified modules with their descendants

Do not mock the ancestors of the specified modules in
autodoc_mock_imports. Only mock the modules themselves and their
descendants (as specified in the docs).

Fix the test configs accordingly.

Signed-off-by: Robin Jarry <robin@jarry.cc>

sphinx/ext/autodoc/importer.py

@@ -23,7 +23,7 @@ from sphinx.util.inspect import isenumclass, safe_getattr
 
 if False:
     # For type annotation
-    from typing import Any, Callable, Dict, Generator, List, Optional, Set  # NOQA
+    from typing import Any, Callable, Dict, Generator, List, Optional  # NOQA
 
 logger = logging.getLogger(__name__)
 
@@ -84,13 +84,7 @@ class _MockModule(ModuleType):
 class _MockImporter(object):
     def __init__(self, names):
         # type: (List[str]) -> None
-        self.base_packages = set()  # type: Set[str]
-        for n in names:
-            # Convert module names:
-            #     ['a.b.c', 'd.e']
-            # to a set of base packages:
-            #     set(['a', 'd'])
-            self.base_packages.add(n.split('.')[0])
+        self.names = names
         self.mocked_modules = []  # type: List[str]
         # enable hook by adding itself to meta_path
         sys.meta_path = sys.meta_path + [self]
@@ -106,9 +100,10 @@ class _MockImporter(object):
 
     def find_module(self, name, path=None):
         # type: (str, str) -> Any
-        base_package = name.split('.')[0]
-        if base_package in self.base_packages:
-            return self
+        # check if name is (or is a descendant of) one of our base_packages
+        for n in self.names:
+            if n == name or name.startswith(n + '.'):
+                return self
         return None
 
     def load_module(self, name):

tests/roots/test-root/autodoc_missing_imports.py

@@ -4,6 +4,8 @@ from missing_module import missing_name
 import missing_package1.missing_module1
 from missing_package2 import missing_module2
 from missing_package3.missing_module3 import missing_name
+import sphinx.missing_module4
+from sphinx.missing_module4 import missing_name2
 
 @missing_name
 def decoratedFunction():
@@ -16,3 +18,5 @@ class TestAutodoc(object):
     def decoratedMethod(self):
         """TestAutodoc::decoratedMethod docstring"""
         return None
+
+sphinx.missing_module4.missing_function(len(missing_name2))

tests/roots/test-root/conf.py

@@ -69,9 +69,10 @@ extlinks = {'issue': ('http://bugs.python.org/issue%s', 'issue '),
 
 autodoc_mock_imports = [
     'missing_module',
-    'missing_package1.missing_module1',
-    'missing_package2.missing_module2',
-    'missing_package3.missing_module3',
+    'missing_package1',
+    'missing_package2',
+    'missing_package3',
+    'sphinx.missing_module4',
 ]
 
 # modify tags from conf.py