Make consider-iterating-dictionary consider memb. check

ChangeLog

@@ -93,6 +93,10 @@ Release date: TBA
 
   Closes #4616
 
+* The ``consider-iterating-dictionary`` checker now also considers membership checks
+
+  Closes #4069
+
 
 What's New in Pylint 2.10.3?
 ============================

doc/whatsnew/2.11.rst

@@ -85,3 +85,7 @@ Other Changes
 
   Closes #1375
   Closes #330
+
+* The ``consider-iterating-dictionary`` checker now also considers membership checks
+
+  Closes #4069

pylint/checkers/refactoring/recommendation_checker.py

@@ -26,7 +26,7 @@ class RecommendationChecker(checkers.BaseChecker):
             "consider-iterating-dictionary",
             "Emitted when the keys of a dictionary are iterated through the .keys() "
             "method. It is enough to just iterate through the dictionary itself, as "
-            'in "for key in dictionary".',
+            'in "for key in dictionary" or "if key in dictionary".',
         ),
         "C0206": (
             "Consider iterating with .items()",
@@ -75,7 +75,13 @@ def _check_consider_iterating_dictionary(self, node: nodes.Call) -> None:
             return
         if node.func.attrname != "keys":
             return
-        if not isinstance(node.parent, (nodes.For, nodes.Comprehension)):
+        if not (
+            isinstance(node.parent, (nodes.For, nodes.Comprehension))
+            or (
+                isinstance(node.parent, nodes.Compare)
+                and isinstance(node.parent.parent, nodes.If)
+            )
+        ):
             return
 
         inferred = utils.safe_infer(node.func)
@@ -84,8 +90,7 @@ def _check_consider_iterating_dictionary(self, node: nodes.Call) -> None:
         ):
             return
 
-        if isinstance(node.parent, (nodes.For, nodes.Comprehension)):
-            self.add_message("consider-iterating-dictionary", node=node)
+        self.add_message("consider-iterating-dictionary", node=node)
 
     def _check_use_maxsplit_arg(self, node: nodes.Call) -> None:
         """Add message when accessing first or last elements of a str.split() or str.rsplit()."""

tests/functional/c/consider/consider_iterating_dictionary.py

@@ -1,4 +1,4 @@
-# pylint: disable=missing-docstring, expression-not-assigned, too-few-public-methods, no-member, import-error, no-self-use, line-too-long, useless-object-inheritance, unnecessary-comprehension
+# pylint: disable=missing-docstring, expression-not-assigned, too-few-public-methods, no-member, import-error, no-self-use, line-too-long, useless-object-inheritance, unnecessary-comprehension, use-dict-literal
 
 from unknown import Unknown
 
@@ -36,3 +36,21 @@ def keys(self):
 COMP1 = [k * 2 for k in DICT.keys()] + [k * 3 for k in DICT.keys()]  # [consider-iterating-dictionary,consider-iterating-dictionary]
 COMP2, COMP3 = [k * 2 for k in DICT.keys()], [k * 3 for k in DICT.keys()]  # [consider-iterating-dictionary,consider-iterating-dictionary]
 SOME_TUPLE = ([k * 2 for k in DICT.keys()], [k * 3 for k in DICT.keys()])  # [consider-iterating-dictionary,consider-iterating-dictionary]
+
+# Checks for membership checks
+if 1 in dict().keys(): # [consider-iterating-dictionary]
+    pass
+if 1 in {}.keys(): # [consider-iterating-dictionary]
+    pass
+if 1 in Unknown().keys():
+    pass
+if 1 in Unknown.keys():
+    pass
+if 1 in CustomClass().keys():
+    pass
+if 1 in dict():
+    pass
+if 1 in dict().values():
+    pass
+if (1, 1) in dict().items():
+    pass

tests/functional/c/consider/consider_iterating_dictionary.txt

@@ -1,15 +1,17 @@
-consider-iterating-dictionary:23:16::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:24:16::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:25:16::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:26:21::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:27:24::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:28:24::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:29:24::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:30:29::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:31:11::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:36:24::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:36:55::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:37:31::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:37:61::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:38:30::Consider iterating the dictionary directly instead of calling .keys()
-consider-iterating-dictionary:38:60::Consider iterating the dictionary directly instead of calling .keys()
+consider-iterating-dictionary:23:16::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:24:16::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:25:16::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:26:21::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:27:24::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:28:24::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:29:24::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:30:29::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:31:11::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:36:24::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:36:55::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:37:31::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:37:61::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:38:30::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:38:60::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:41:8::Consider iterating the dictionary directly instead of calling .keys():HIGH
+consider-iterating-dictionary:43:8::Consider iterating the dictionary directly instead of calling .keys():HIGH