Fix bug in b030 (#364)

* Update _flatten_excepthandler with more logic

* Shift some code left

* Reformat, _duh_

---------

Co-authored-by: Aaron Cunningham <aaron.cu@enervee.com>

bugbear.py

@@ -190,11 +190,18 @@ def _is_identifier(arg):
 
 
 def _flatten_excepthandler(node):
-    if isinstance(node, ast.Tuple):
-        for elt in node.elts:
-            yield from _flatten_excepthandler(elt)
-    else:
+    if not isinstance(node, ast.Tuple):
         yield node
+        return
+    expr_list = node.elts.copy()
+    while len(expr_list):
+        expr = expr_list.pop(0)
+        if isinstance(expr, ast.Starred) and isinstance(
+            expr.value, (ast.List, ast.Tuple)
+        ):
+            expr_list.extend(expr.value.elts)
+            continue
+        yield expr
 
 
 def _check_redundant_excepthandlers(names, node):

tests/b030.py

@@ -1,6 +1,11 @@
 try:
     pass
-except (ValueError, (RuntimeError, (KeyError, TypeError))):  # ok
+except (ValueError, (RuntimeError, (KeyError, TypeError))):  # error
+    pass
+
+try:
+    pass
+except (ValueError, *(RuntimeError, *(KeyError, TypeError))):  # ok
     pass
 
 try:

tests/test_bugbear.py

@@ -456,8 +456,9 @@ def test_b030(self):
         bbc = BugBearChecker(filename=str(filename))
         errors = list(bbc.run())
         expected = self.errors(
-            B030(8, 0),
+            B030(3, 0),
             B030(13, 0),
+            B030(18, 0),
         )
         self.assertEqual(errors, expected)