Add import-based submodule detection for preferred-modules (#8186)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

2 files changed, 58 insertions, 1 deletions

diff --git a/tests/checkers/unittest_imports.py b/tests/checkers/unittest_imports.py
index 40aa8432a..8aa062cf4 100644
--- a/tests/checkers/unittest_imports.py
+++ b/tests/checkers/unittest_imports.py
@@ -123,7 +123,7 @@ class TestImportsChecker(CheckerTestCase):
         # test preferred-modules case with base module import
         Run(
             [
-                f"{os.path.join(REGR_DATA, 'preferred_module')}",
+                f"{os.path.join(REGR_DATA, 'preferred_module/unpreferred_module.py')}",
                 "-d all",
                 "-e preferred-module",
                 # prefer sys instead of os (for triggering test)
@@ -138,6 +138,60 @@ class TestImportsChecker(CheckerTestCase):
         # assert there were no errors
         assert len(errors) == 0
 
+        # test preferred-modules trigger case with submodules
+        Run(
+            [
+                f"{os.path.join(REGR_DATA, 'preferred_module/unpreferred_submodule.py')}",
+                "-d all",
+                "-e preferred-module",
+                # prefer os.path instead of pathlib (for triggering test)
+                "--preferred-modules=os.path:pathlib",
+            ],
+            exit=False,
+        )
+        output, errors = capsys.readouterr()
+
+        # assert that we saw preferred-modules triggered
+        assert "Prefer importing 'pathlib' instead of 'os.path'" in output
+        # assert there were no errors
+        assert len(errors) == 0
+
+        # test preferred-modules ignore case with submodules
+        Run(
+            [
+                f"{os.path.join(REGR_DATA, 'preferred_module/unpreferred_submodule.py')}",
+                "-d all",
+                "-e preferred-module",
+                # prefer pathlib instead of os.stat (for untriggered test)
+                "--preferred-modules=os.stat:pathlib",
+            ],
+            exit=False,
+        )
+        output, errors = capsys.readouterr()
+
+        # assert that we didn't see preferred-modules triggered
+        assert "Your code has been rated at 10.00/10" in output
+        # assert there were no errors
+        assert len(errors) == 0
+
+        # test preferred-modules base module for implemented submodule (from ... import)
+        Run(
+            [
+                f"{os.path.join(REGR_DATA, 'preferred_module/unpreferred_submodule.py')}",
+                "-d all",
+                "-e preferred-module",
+                # prefer pathlib instead of os (for triggering test)
+                "--preferred-modules=os:pathlib",
+            ],
+            exit=False,
+        )
+        output, errors = capsys.readouterr()
+
+        # assert that we saw preferred-modules triggered with base module
+        assert "Prefer importing 'pathlib' instead of 'os'" in output
+        # assert there were no errors
+        assert len(errors) == 0
+
     @staticmethod
     def test_allow_reexport_package(capsys: CaptureFixture[str]) -> None:
         """Test --allow-reexport-from-package option."""
diff --git a/tests/regrtest_data/preferred_module/unpreferred_submodule.py b/tests/regrtest_data/preferred_module/unpreferred_submodule.py
new file mode 100644
index 000000000..22c61ffbe
--- /dev/null
+++ b/tests/regrtest_data/preferred_module/unpreferred_submodule.py
@@ -0,0 +1,3 @@
+from os import path, getrandom
+
+path(".")