SIM106: Remove false-positives (#95)

Don't trigger if the 'else' block ends with a ValueError or a NotImplementedError.

Closes #87

flake8_simplify.py

@@ -421,6 +421,18 @@ def _get_sim106(node: ast.If) -> List[Tuple[int, int, str]]:
     )
     if not (just_one or many):
         return errors
+    ast_raise = node.orelse[-1]
+    if not isinstance(ast_raise, ast.Raise):
+        return errors
+    ast_raised = ast_raise.exc
+    if (
+        isinstance(ast_raised, ast.Call)
+        and ast_raised.func
+        and isinstance(ast_raised.func, ast.Name)
+        and ast_raised.func.id in ["ValueError", "NotImplementedError"]
+    ):
+        return errors
+
     errors.append((node.lineno, node.col_offset, SIM106))
     return errors
 

tests/test_simplify.py

@@ -195,14 +195,33 @@ def test_sim106():
     assert ret == {"1:0 SIM106 Handle error-cases first"}
 
 
-def test_sim106_no():
-    ret = _results(
+@pytest.mark.parametrize(
+    "s",
+    (
+        """if image_extension in ['.jpg', '.jpeg']:
+    return 'JPEG'
+elif image_extension in ['.png']:
+    return 'PNG'
+else:
+    raise ValueError("Unknwon image extension {image extension}")""",
+        """if image_extension in ['.jpg', '.jpeg']:
+    return 'JPEG'
+elif image_extension in ['.png']:
+    return 'PNG'
+else:
+    logger.error("Unknwon image extension {image extension}")
+    raise ValueError("Unknwon image extension {image extension}")""",
         """if cond:
     raise Exception
 else:
-    raise Exception"""
-    )
-    assert ret == set()
+    raise Exception""",
+    ),
+    ids=["ValueError", "ValueError-with-logging", "TwoExceptions"],
+)
+def test_sim106_false_positive(s):
+    ret = _results(s)
+    for el in ret:
+        assert "SIM106" not in el
 
 
 def test_sim107():