Add test for ModuleNotFoundError fix (pylint-dev#7938)

tests/regrtest_data/importing_plugin/importing_plugin.py

@@ -0,0 +1,32 @@
+from importlib import import_module
+
+from pylint.checkers import BaseChecker
+from pylint.lint.pylinter import PyLinter
+
+
+class ImportingChecker(BaseChecker):
+    options = (
+        (
+            "settings-module",
+            {
+                "default": "settings",
+                "type": "string",
+                "metavar": "<settings module>"
+            },
+        ),
+    )
+
+    msgs = {
+        "E9999": (
+            "Importing checker error message",
+            "importing-checker-error",
+            "Importing checker error message",
+        ),
+    }
+
+    def open(self) -> None:
+        import_module(self.linter.config.settings_module)
+
+
+def register(linter: "PyLinter") -> None:
+    linter.register_checker(ImportingChecker(linter))

tests/test_self.py

@@ -869,6 +869,23 @@ def test_modify_sys_path() -> None:
                 modify_sys_path()
             assert sys.path == paths[1:]
 
+    @staticmethod
+    def test_plugin_that_imports_from_open() -> None:
+        """Test that a plugin that imports a source file from a checker open()
+        function (ala pylint_django) does not raise an exception."""
+
+        project_path = join(HERE, "regrtest_data", "settings_project")
+        plugin_path = join(HERE, "regrtest_data", "importing_plugin")
+        # Enable --load-plugins=importing_plugin
+        sys.path.append(plugin_path)
+        with _test_cwd():
+            os.chdir(project_path)
+            Run(
+                ["--load-plugins=importing_plugin", "models.py"],
+                exit=False,
+            )
+        sys.path.remove(plugin_path)
+
     @pytest.mark.parametrize(
         "args",
         [