[#137] Fix error when list with empty env var and subcast (#143)

sloria · Mar 22, 2020 · d8f75d7 · d8f75d7
1 parent 1a4adbf
commit d8f75d7
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diff --git a/environs/__init__.py b/environs/__init__.py
@@ -136,7 +136,9 @@ def _make_list_field(*, subcast: typing.Optional[type], **kwargs) -> ma.fields.L
 
 
 def _preprocess_list(value: typing.Union[str, typing.Iterable], **kwargs) -> typing.Iterable:
-    return value if ma.utils.is_iterable_but_not_string(value) else typing.cast(str, value).split(",")
+    if ma.utils.is_iterable_but_not_string(value):
+        return value
+    return typing.cast(str, value).split(",") if value != "" else []
 
 
 def _preprocess_dict(

diff --git a/tests/test_environs.py b/tests/test_environs.py
@@ -81,6 +81,11 @@ def test_list_with_subcast(self, set_env, env):
         assert env.list("LIST", subcast=int) == [1, 2, 3]
         assert env.list("LIST", subcast=float) == [1.0, 2.0, 3.0]
 
+    def test_list_with_empty_env_and_subcast(self, set_env, env):
+        set_env({"LIST": ""})
+        assert env.list("LIST", subcast=int) == []
+        assert env.list("LIST", subcast=float) == []
+
     def test_bool(self, set_env, env):
         set_env({"TRUTHY": "1", "FALSY": "0"})
         assert env.bool("TRUTHY") is True