Better and faster implementation of instance_has_bool

Author: Pierre-Sassoulas

pylint/checkers/refactoring/len_checker.py

@@ -107,7 +107,11 @@ def visit_call(self, node):
 
     @staticmethod
     def instance_has_bool(class_def: astroid.ClassDef) -> bool:
-        return any(hasattr(f, "name") and f.name == "__bool__" for f in class_def.body)
+        try:
+            class_def.getattr("__bool__")
+        except astroid.AttributeInferenceError:
+            ...
+        return False
 
     @utils.check_messages("len-as-condition")
     def visit_unaryop(self, node):

tests/functional/l/len_checks.py

@@ -120,9 +120,7 @@ class ChildClassWithoutBool(ClassWithoutBool):
         pass
 
     assert len(ClassWithBool())
-    # We could expect to not have a len-as-condition for ChildClassWithBool,
-    # but I don't think the required analysis is worth it.
-    assert len(ChildClassWithBool()) # [len-as-condition]
+    assert len(ChildClassWithBool())
     assert len(ClassWithoutBool())  # [len-as-condition]
     assert len(ChildClassWithoutBool())  # [len-as-condition]
     assert len(range(0))  # [len-as-condition]

tests/functional/l/len_checks.txt

@@ -13,12 +13,12 @@ len-as-condition:98:github_issue_1331_v3:Do not use `len(SEQUENCE)` without comp
 len-as-condition:101:github_issue_1331_v4:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:103::Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:104::Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
+len-as-condition:124:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:125:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:126:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:127:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:128:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:129:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:130:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
 len-as-condition:131:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
-len-as-condition:132:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
-len-as-condition:163:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty
+len-as-condition:161:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty