Fix error message for prefixed var

close #102

CHANGELOG.md

@@ -24,6 +24,13 @@ def https_url(value):
     return "https://" + value
 ```
 
+Bug fixes:
+
+- Fix error message for prefixed variables ([#102](https://github.com/sloria/environs/issues/102)).
+  Thanks [AGeekInside](https://github.com/AGeekInside) for reporting.
+
+Other changes:
+
 - _Backwards-incompatible_: Rename `Env.__parser_map__` to `Env.__custom_parsers__`.
 
 ## 5.2.1 (2019-08-08)

environs.py

@@ -52,8 +52,9 @@ def method(
             field = typing.cast(FieldFactory, field_or_factory)(subcast=subcast, missing=missing, **kwargs)
         parsed_key, raw_value, proxied_key = self._get_from_environ(name, ma.missing)
         self._fields[parsed_key] = field
+        source_key = proxied_key or parsed_key
         if raw_value is ma.missing and field.missing is ma.missing:
-            raise EnvError('Environment variable "{}" not set'.format(proxied_key or parsed_key))
+            raise EnvError('Environment variable "{}" not set'.format(source_key))
         if raw_value or raw_value == "":
             value = raw_value
         else:
@@ -63,7 +64,9 @@ def method(
         try:
             value = field.deserialize(value)
         except ma.ValidationError as error:
-            raise EnvError('Environment variable "{}" invalid: {}'.format(name, error.args[0])) from error
+            raise EnvError(
+                'Environment variable "{}" invalid: {}'.format(source_key, error.args[0])
+            ) from error
         else:
             self._values[parsed_key] = value
             return value

tests/test_environs.py

@@ -435,6 +435,11 @@ def test_dump_with_prefixed(self, env):
             env("NOT_FOUND", "mydefault") == "mydefault"
         assert env.dump() == {"APP_STR": "foo", "APP_INT": 42, "APP_NOT_FOUND": "mydefault"}
 
+    def test_error_message_for_prefixed_var(self, env):
+        with env.prefixed("APP_"):
+            with pytest.raises(environs.EnvError, match='Environment variable "APP_INT" invalid'):
+                env.int("INT", validate=lambda val: val < 42)
+
 
 class TestNestedPrefix:
     @pytest.fixture(autouse=True)