From 3d6389b97e8f9416304185a1babfe49e8a0dc348 Mon Sep 17 00:00:00 2001
From: Sergei Lebedev <185856+superbobry@users.noreply.github.com>
Date: Sun, 27 Jun 2021 19:11:54 +0100
Subject: [PATCH] VariableChecker now accounts for attribute lookups in type
 comments (#4604)

* VariableChecker now accounts for attribute lookups in type comments

Prior to this commit VariableChecker did not recurse into attribute lookups
in type comments. This lead to false positive unused-import messages in e.g.

    import collections
    d = ...  # type: collections.OrderedDict

Fixes #4603
---
 CONTRIBUTORS.txt                     |  2 ++
 ChangeLog                            |  5 +++++
 pylint/checkers/variables.py         |  4 ++++
 pylint/constants.py                  |  2 ++
 tests/checkers/unittest_variables.py | 20 ++++++++++++++++++++
 5 files changed, 33 insertions(+)

diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index b1de7ff30e..05e4a31e18 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -503,3 +503,5 @@ contributors:
 * Markus Siebenhaar: contributor
 
 * Lorena Buciu (lorena-b): contributor
+
+* Sergei Lebedev (superbobry): contributor
diff --git a/ChangeLog b/ChangeLog
index a0f12a7a88..7172972b82 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -186,6 +186,11 @@ Closes #4555
 
   Closes #4023
 
+* Fix ``unused-import`` false positive for imported modules referenced in
+  attribute lookups in type comments.
+
+  Closes #4603
+
 
 What's New in Pylint 2.8.3?
 ===========================
diff --git a/pylint/checkers/variables.py b/pylint/checkers/variables.py
index 3ddafd5994..8a46375097 100644
--- a/pylint/checkers/variables.py
+++ b/pylint/checkers/variables.py
@@ -1826,6 +1826,10 @@ def _store_type_annotation_node(self, type_annotation):
             self._type_annotation_names.append(type_annotation.name)
             return
 
+        if isinstance(type_annotation, astroid.Attribute):
+            self._store_type_annotation_node(type_annotation.expr)
+            return
+
         if not isinstance(type_annotation, astroid.Subscript):
             return
 
diff --git a/pylint/constants.py b/pylint/constants.py
index b95d701c04..786cde7d02 100644
--- a/pylint/constants.py
+++ b/pylint/constants.py
@@ -1,6 +1,7 @@
 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 # For details: https://github.com/PyCQA/pylint/blob/master/LICENSE
 
+import platform
 import sys
 
 import astroid
@@ -11,6 +12,7 @@
 PY39_PLUS = sys.version_info[:2] >= (3, 9)
 PY310_PLUS = sys.version_info[:2] >= (3, 10)
 
+IS_PYPY = platform.python_implementation() == "PyPy"
 
 PY_EXTS = (".py", ".pyc", ".pyo", ".pyw", ".so", ".dll")
 
diff --git a/tests/checkers/unittest_variables.py b/tests/checkers/unittest_variables.py
index 90daa8d5d1..2a590708d9 100644
--- a/tests/checkers/unittest_variables.py
+++ b/tests/checkers/unittest_variables.py
@@ -21,11 +21,13 @@
 import os
 import re
 import sys
+import unittest
 from pathlib import Path
 
 import astroid
 
 from pylint.checkers import variables
+from pylint.constants import IS_PYPY
 from pylint.interfaces import UNDEFINED
 from pylint.testutils import CheckerTestCase, Message, linter, set_config
 
@@ -191,6 +193,24 @@ def my_method(self) -> MyType:
         with self.assertNoMessages():
             self.walk(module)
 
+    @unittest.skipIf(IS_PYPY, "PyPy does not parse type comments")
+    def test_attribute_in_type_comment(self):
+        """Ensure attribute lookups in type comments are accounted for.
+
+        https://github.com/PyCQA/pylint/issues/4603
+        """
+        module = astroid.parse(
+            """
+        import foo
+        from foo import Bar, Boo
+        a = ... # type: foo.Bar
+        b = ... # type: foo.Bar[Boo]
+        c = ... # type: Bar.Boo
+        """
+        )
+        with self.assertNoMessages():
+            self.walk(module)
+
 
 class TestVariablesCheckerWithTearDown(CheckerTestCase):