fix incorrect basenames caused by a lack of __init__.py

The problem was caused by
   pylint-dev/astroid#2589, changing the
  package discovery.

Since tests/reporters/ didn't have `__init__.py`, the new package
   discovery would resolve module names as one level higher than
   desired (so, `unittest_reporting` instead of
   `reporters.unittest_reporting`). We're fixing this, by adding the
   appropriate `__init__.py`.

We're also adding the `ModuleDescriptionDict` corresponding to the new
   `__init__.py` to the `expand_modules` tests.

The changes in `expand_modules.py` are small optimizations mostly done
   in the process of understanding what is happening there.

pylint/lint/expand_modules.py

@@ -136,32 +136,28 @@ def expand_modules(
             is_namespace = modutils.is_namespace(spec)
             is_directory = modutils.is_directory(spec)
         if not is_namespace:
-            if filepath in result:
-                # Always set arg flag if module explicitly given.
-                result[filepath]["isarg"] = True
-            else:
-                result[filepath] = {
-                    "path": filepath,
-                    "name": modname,
-                    "isarg": True,
-                    "basepath": filepath,
-                    "basename": modname,
-                    "isignored": False,
-                }
+            default: ModuleDescriptionDict = {
+                "path": filepath,
+                "name": modname,
+                "isarg": True,
+                "basepath": filepath,
+                "basename": modname,
+                "isignored": False,
+            }
+            result.setdefault(filepath, default)["isarg"] = True
         has_init = (
-            not (modname.endswith(".__init__") or modname == "__init__")
-            and os.path.basename(filepath) == "__init__.py"
+            modparts[-1] != "__init__" and os.path.basename(filepath) == "__init__.py"
         )
         if has_init or is_namespace or is_directory:
             for subfilepath in modutils.get_module_files(
-                os.path.dirname(filepath) or ".", ignore_list, list_all=is_namespace
+                os.path.dirname(filepath) or ".", [], list_all=is_namespace
             ):
                 subfilepath = os.path.normpath(subfilepath)
                 if filepath == subfilepath:
                     continue
-                if _is_in_ignore_list_re(
-                    os.path.basename(subfilepath), ignore_list_re
-                ) or _is_in_ignore_list_re(subfilepath, ignore_list_paths_re):
+                if _is_ignored_file(
+                    subfilepath, ignore_list, ignore_list_re, ignore_list_paths_re
+                ):
                     result[subfilepath] = {
                         "path": subfilepath,
                         "name": "",

tests/lint/unittest_expand_modules.py

@@ -127,20 +127,28 @@ def test__is_in_ignore_list_re_match() -> None:
 # A directory that is not a python package.
 REPORTERS_PATH = Path(__file__).parent.parent / "reporters"
 test_reporters = {  # pylint: disable=consider-using-namedtuple-or-dataclass
-    str(REPORTERS_PATH / "unittest_json_reporter.py"): {
-        "path": str(REPORTERS_PATH / "unittest_json_reporter.py"),
-        "name": "reporters.unittest_json_reporter",
-        "isarg": False,
+    str(REPORTERS_PATH / "__init__.py"): {
+        "basename": "reporters",
         "basepath": str(REPORTERS_PATH / "__init__.py"),
+        "isarg": True,
+        "name": "reporters",
+        "path": str(REPORTERS_PATH / "__init__.py"),
+        "isignored": False,
+    },
+    str(REPORTERS_PATH / "unittest_json_reporter.py"): {
         "basename": "reporters",
+        "basepath": str(REPORTERS_PATH / "__init__.py"),
+        "isarg": False,
+        "name": "reporters.unittest_json_reporter",
+        "path": str(REPORTERS_PATH / "unittest_json_reporter.py"),
         "isignored": False,
     },
     str(REPORTERS_PATH / "unittest_reporting.py"): {
+        "basename": "reporters",
+        "basepath": str(REPORTERS_PATH / "__init__.py"),
+        "isarg": False,
         "path": str(REPORTERS_PATH / "unittest_reporting.py"),
         "name": "reporters.unittest_reporting",
-        "isarg": False,
-        "basepath": str(REPORTERS_PATH / "__init__.py"),
-        "basename": "reporters",
         "isignored": False,
     },
 }