SIM908: Fix false-positive (#128)

Ensure that the assigned name is equal to the name in the if.test

See #126

flake8_simplify/rules/ast_if.py

@@ -341,6 +341,12 @@ def get_sim908(node: ast.If) -> List[Tuple[int, int, str]]:
         and isinstance(node.body[0].targets[0], ast.Name)
     ):
         return errors
+
+    test_var = node.test.left
+    slice_var = node.body[0].value.slice
+    if to_source(slice_var) != to_source(test_var):
+        return errors
+
     key = to_source(node.test.left)
     dictname = to_source(node.test.comparators[0])
     errors.append(

tests/test_900_rules.py

@@ -154,6 +154,25 @@ def test_sim908():
     }
 
 
+@pytest.mark.parametrize(
+    "s",
+    (
+        # Credits to jonyscathe for this example:
+        # https://github.com/MartinThoma/flake8-simplify/issues/126
+        """if "." in resistance:
+    # Swap '.' with suffix
+    resistance = resistance.replace(".", resistance[-1])[:-1]""",
+        """if "." in iterable:
+    iterable = iterable[:-1]""",
+    ),
+    ids=("issue-125", "issue-125-simplified"),
+)
+def test_sim908_false_positive(s):
+    results = _results(s)
+    for el in results:
+        assert "SIM908" not in el
+
+
 @pytest.mark.parametrize(
     ("s", "msg"),
     (