Fix unused-import to checkdummy-variables-rgx (#8566)

Resolve #8500

Co-authored-by: Pierre Sassoulas <[email protected]>

doc/whatsnew/fragments/8500.false_positive

@@ -0,0 +1,3 @@
+Fixed `unused-import` so that it observes the `dummy-variables-rgx` option.
+
+Closes #8500

pylint/checkers/variables.py

@@ -3055,6 +3055,13 @@ def _check_imports(self, not_consumed: dict[str, list[nodes.NodeNG]]) -> None:
                     imported_name in self._type_annotation_names
                     or as_name in self._type_annotation_names
                 )
+
+                is_dummy_import = (
+                    as_name
+                    and self.linter.config.dummy_variables_rgx
+                    and self.linter.config.dummy_variables_rgx.match(as_name)
+                )
+
                 if isinstance(stmt, nodes.Import) or (
                     isinstance(stmt, nodes.ImportFrom) and not stmt.modname
                 ):
@@ -3065,12 +3072,11 @@ def _check_imports(self, not_consumed: dict[str, list[nodes.NodeNG]]) -> None:
                         # because they can be imported for exporting.
                         continue
 
-                    if is_type_annotation_import:
+                    if is_type_annotation_import or is_dummy_import:
                         # Most likely a typing import if it wasn't used so far.
+                        # Also filter dummy variables.
                         continue
 
-                    if as_name == "_":
-                        continue
                     if as_name is None:
                         msg = f"import {imported_name}"
                     else:
@@ -3088,8 +3094,9 @@ def _check_imports(self, not_consumed: dict[str, list[nodes.NodeNG]]) -> None:
                         # __future__ import in another module.
                         continue
 
-                    if is_type_annotation_import:
+                    if is_type_annotation_import or is_dummy_import:
                         # Most likely a typing import if it wasn't used so far.
+                        # Also filter dummy variables.
                         continue
 
                     if imported_name == "*":

tests/checkers/unittest_typecheck.py

@@ -10,7 +10,7 @@
 from pylint.testutils import CheckerTestCase, MessageTest, set_config
 
 try:
-    from coverage import tracer as _  # pylint: disable=unused-import
+    from coverage import tracer as _
 
     C_EXTENTIONS_AVAILABLE = True
 except ImportError:

tests/functional/i/import_dummy.py

@@ -0,0 +1,5 @@
+"""Testing importing module as dummy variable."""
+import gettext as _
+import sys as __
+import typing as ___dummy
+from base64 import b64encode as ____dummy