Fix #53: crash in RewriteEmptyContainers.

Instagram · Jan 11, 2018 · 13de516 · 13de516
1 parent d35f3e9
commit 13de516
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diff --git a/CHANGES.rst b/CHANGES.rst
@@ -4,6 +4,9 @@ Changelog
 master
 ------
 
+* Fix crash in RewriteEmptyContainers rewriter if a parameter has only empty
+  container types in traces (and more than one). Fixes #53.
+
 
 18.1.10
 -------

diff --git a/monkeytype/typing.py b/monkeytype/typing.py
@@ -177,7 +177,9 @@ def _is_empty(self, typ):
     def rewrite_Union(self, union):
         elems = tuple(
             self.rewrite(e) for e in union.__args__ if not self._is_empty(e))
-        return Union[elems]
+        if elems:
+            return Union[elems]
+        return union
 
 
 class RewriteConfigDict(TypeRewriter):

diff --git a/tests/test_typing.py b/tests/test_typing.py
@@ -118,6 +118,7 @@ class TestRemoveEmptyContainers:
             ),
             (Union[str, int], Union[str, int]),
             (Dict[str, Union[List[str], List[Any]]], Dict[str, List[str]]),
+            (Union[List[Any], Set[Any]], Union[List[Any], Set[Any]])
         ],
     )
     def test_rewrite(self, typ, expected):