[Pylint] Disallow using legacy type hinting

tools/pylint-extensions/azure-pylint-guidelines-checker/README.md

@@ -92,3 +92,4 @@ In the case of a false positive, use the disable command to remove the pylint er
 | docstring-keyword-should-match-keyword-only        | Docstring keyword arguments and keyword-only method arguments should match.                                                                                          | pylint:disable=docstring-keyword-should-match-keyword-only          | [link](https://azure.github.io/azure-sdk/python_documentation.html#docstrings)                          |
 | docstring-type-do-not-use-class                    | Docstring type is formatted incorrectly. Do not use `:class` in docstring type.                                                                                      | pylint:disable=docstring-type-do-not-use-class                      | [link](https://sphinx-rtd-tutorial.readthedocs.io/en/latest/docstrings.html)                            |
 | no-typing-import-in-type-check                     | Do not import typing under TYPE_CHECKING.                                                                                                                            | pylint:disable=no-typing-import-in-type-check                       | No Link.                                                                                                |
+| do-not-use-legacy-typing                           | Do not use legacy (<Python 3.8) type hinting comments                                                                                                             | pylint:disable=do-not-use-legacy-typing                             | No Link.

tools/pylint-extensions/azure-pylint-guidelines-checker/pylint_guidelines_checker.py

@@ -2750,6 +2750,29 @@ def visit_import(self, node):
         except:
             pass
 
+class DoNotUseLegacyTyping(BaseChecker):
+
+    """ Rule to check that we aren't using legacy typing using comments. """
+
+    name = "do-not-use-legacy-typing"
+    priority = -1
+    msgs = {
+        "C4761": (
+            "Do not use legacy typing using comments.",
+            "do-not-use-legacy-typing",
+            "Do not use legacy typing using comments. Python 2 is no longer supported, use Python 3.9+ type hints instead.",
+        ),
+    }
+
+    def visit_functiondef(self, node):
+        """Check that we aren't using legacy typing."""
+        if node.is_function and (node.type_comment_args or node.type_comment_returns):
+            self.add_message(
+                msgid=f"do-not-use-legacy-typing",
+                node=node,
+                confidence=None,
+            )
+
 # if a linter is registered in this function then it will be checked with pylint
 def register(linter):
     linter.register_checker(ClientsDoNotUseStaticMethods(linter))
@@ -2782,6 +2805,8 @@ def register(linter):
     linter.register_checker(DoNotImportLegacySix(linter))
     linter.register_checker(NoLegacyAzureCoreHttpResponseImport(linter))
     linter.register_checker(NoImportTypingFromTypeCheck(linter))
+    linter.register_checker(DoNotUseLegacyTyping(linter))
+
 
     # disabled by default, use pylint --enable=check-docstrings if you want to use it
     linter.register_checker(CheckDocstringParameters(linter))

tools/pylint-extensions/azure-pylint-guidelines-checker/tests/test_pylint_custom_plugins.py

@@ -4829,4 +4829,54 @@ def test_allowed_import_else(self):
             self.checker.visit_importfrom(ima)
             self.checker.visit_import(imb)
             self.checker.visit_import(imc)
-            self.checker.visit_importfrom(imd)
+            self.checker.visit_importfrom(imd)
+
+class TestCheckDoNotUseLegacyTyping(pylint.testutils.CheckerTestCase):
+    """Test that we are blocking disallowed legacy typing practices"""
+
+    CHECKER_CLASS = checker.DoNotUseLegacyTyping
+
+    def test_disallowed_typing(self):
+        """Check that illegal method typing comments raise warnings"""
+        fdef = astroid.extract_node(
+            """
+            def function(x): #@
+                # type: (str) -> str
+                pass
+            """
+        )
+
+        with self.assertAddsMessages(
+            pylint.testutils.MessageTest(
+                msg_id="do-not-use-legacy-typing",
+                line=2,
+                node=fdef,
+                col_offset=0,
+                end_line=2,
+                end_col_offset=12,
+            )
+        ):
+            self.checker.visit_functiondef(fdef)
+
+    def test_allowed_typing(self):
+        """Check that allowed method typing comments don't raise warnings"""
+        fdef = astroid.extract_node(
+            """
+            def function(x: str) -> str: #@
+                pass
+            """
+        )
+        with self.assertNoMessages():
+            self.checker.visit_functiondef(fdef)
+
+    def test_arbitrary_comments(self):
+        """Check that arbitrary comments don't raise warnings"""
+        fdef = astroid.extract_node(
+            """
+            def function(x): #@
+                # This is a comment
+                pass
+            """
+        )
+        with self.assertNoMessages():
+            self.checker.visit_functiondef(fdef)