Fix a false positive for unbalanced-tuple-unpacking. (#10724)

* Fix a false positive for ``unbalanced-tuple-unpacking`` when a tuple is assigned to a function call and the structure of the function's return value is ambiguous.

Closes #10721

Co-authored-by: Pierre Sassoulas <[email protected]>

Author: mbyrnepr2

doc/whatsnew/fragments/10721.false_positive

@@ -0,0 +1,3 @@
+Fix a false positive for ``unbalanced-tuple-unpacking`` when a tuple is assigned to a function call and the structure of the function's return value is ambiguous.
+
+Closes #10721

pylint/checkers/variables.py

@@ -2162,11 +2162,10 @@ def visit_assign(self, node: nodes.Assign) -> None:
         # Check if we have starred nodes.
         if any(isinstance(target, nodes.Starred) for target in targets):
             return
-
         try:
-            inferred = utils.safe_infer(node.value)
-            if inferred is not None:
-                self._check_unpacking(inferred, node, targets)
+            inferred = node.value.inferred()
+            if inferred is not None and len(inferred) == 1:
+                self._check_unpacking(inferred[0], node, targets)
         except astroid.InferenceError:
             return
 

tests/functional/u/unbalanced/unbalanced_tuple_unpacking.py

@@ -167,3 +167,14 @@ def my_function(mystring):
 # Using a lot of args, so we have a high probability to still trigger the problem if
 # we add arguments to our unittest command later
 (p, q, r, s, t, u, v, w, x, y, z) = sys.argv  # pylint: disable=invalid-name
+
+
+# https://github.com/pylint-dev/pylint/issues/10721
+def fruit(apple: int, pear: int, kiwi: int | None = None) -> tuple[int, int] | tuple[int, int, int]:
+    return (apple, pear) if kiwi is None else (apple, pear, kiwi)
+
+def main():
+    _, _ = fruit(1, 2)
+    _, _ = fruit(1, 2, 3)  # known false negative, requires better None comprehension in astroid
+    _, _, _ = fruit(1, 2)  # known false negative, requires better None comprehension in astroid
+    _, _, _ = fruit(1, 2, 3)