Fix E1102 / not-callable false positive for property that returns a lambda function conditionally (#6068)

Co-authored-by: Jacob Walls <[email protected]>
Co-authored-by: Daniël van Noord <[email protected]>
Co-authored-by: Pierre Sassoulas <[email protected]>

Author: 4 people

ChangeLog

@@ -24,6 +24,9 @@ Release date: TBA
   * functions & classes which contain both a docstring and an ellipsis.
   * A body which contains an ellipsis ``nodes.Expr`` node & at least one other statement.
 
+* Only raise ``not-callable`` when all the inferred values of a property are not callable.
+
+  Closes #5931
 
 
 What's New in Pylint 2.13.4?

doc/whatsnew/2.13.rst

@@ -575,3 +575,7 @@ Other Changes
   separated (e.g. by parens).
 
   Closes #5769
+
+* Only raise ``not-callable`` when all the inferred values of a property are not callable.
+
+  Closes #5931

pylint/checkers/typecheck.py

@@ -1217,20 +1217,22 @@ def _check_uninferable_call(self, node):
             # Decorated, see if it is decorated with a property.
             # Also, check the returns and see if they are callable.
             if decorated_with_property(attr):
-
                 try:
-                    all_returns_are_callable = all(
-                        return_node.callable() or return_node is astroid.Uninferable
-                        for return_node in attr.infer_call_result(node)
-                    )
+                    call_results = list(attr.infer_call_result(node))
                 except astroid.InferenceError:
                     continue
 
-                if not all_returns_are_callable:
-                    self.add_message(
-                        "not-callable", node=node, args=node.func.as_string()
-                    )
-                    break
+                if all(
+                    return_node is astroid.Uninferable for return_node in call_results
+                ):
+                    # We were unable to infer return values of the call, skipping
+                    continue
+
+                if any(return_node.callable() for return_node in call_results):
+                    # Only raise this issue if *all* the inferred values are not callable
+                    continue
+
+                self.add_message("not-callable", node=node, args=node.func.as_string())
 
     def _check_argument_order(self, node, call_site, called, called_param_names):
         """Match the supplied argument names against the function parameters.

tests/functional/n/not_callable.py

@@ -200,3 +200,27 @@ def get_number(arg):
 
 
 get_number(10)()  # [not-callable]
+
+class Klass:
+    def __init__(self):
+        self._x = None
+
+    @property
+    def myproperty(self):
+        if self._x is None:
+            self._x = lambda: None
+        return self._x
+
+myobject = Klass()
+myobject.myproperty()
+
+class Klass2:
+    @property
+    def something(self):
+        if __file__.startswith('s'):
+            return str
+
+        return 'abcd'
+
+obj2 = Klass2()
+obj2.something()