Merge pull request #773 from krassowski/union-from-string

ipython · Sep 9, 2022 · 367ac77 · 367ac77
2 parents 4a0a708 + 9493030
commit 367ac77
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diff --git a/traitlets/tests/test_traitlets.py b/traitlets/tests/test_traitlets.py
@@ -3136,6 +3136,14 @@ def test_tcp_from_string(s, expected):
     _from_string_test(TCPAddress, s, expected)
 
 
+@pytest.mark.parametrize(
+    "s, expected",
+    [("[]", []), ("{}", "{}")],
+)
+def test_union_of_list_and_unicode_from_string(s, expected):
+    _from_string_test(Union([List(), Unicode()]), s, expected)
+
+
 def test_all_attribute():
     """Verify all trait types are added to `traitlets.__all__`"""
     names = dir(traitlets)

diff --git a/traitlets/traitlets.py b/traitlets/traitlets.py
@@ -2179,6 +2179,15 @@ def __or__(self, other):
         else:
             return Union(self.trait_types + [other])
 
+    def from_string(self, s):
+        for trait_type in self.trait_types:
+            try:
+                v = trait_type.from_string(s)
+                return trait_type.validate(None, v)
+            except TraitError:
+                continue
+        self.error(None, s)
+
 
 # -----------------------------------------------------------------------------
 # Basic TraitTypes implementations/subclasses