Add Support for marshmallow.fields.Enum in marshmallow >= v3.18

This fixes #169.

Detailed changes:
* Introduce distinction between Enums imports from `marshmallow_enum` and `marshmallow.fields` (the latter are refered to as "marshmallow native" Enums)
* Add function to find out if the version of marshmallow used supports the native Enum type
* Add test cases that reproduce the issue
* Adapt the code to also support the native enums

marshmallow_jsonschema/base.py

@@ -9,8 +9,21 @@
 from marshmallow.class_registry import get_class
 from marshmallow.decorators import post_dump
 from marshmallow.utils import _Missing
-
 from marshmallow import INCLUDE, EXCLUDE, RAISE
+# marshmallow.fields.Enum support has been added in marshmallow v3.18
+# see https://github.com/marshmallow-code/marshmallow/blob/dev/CHANGELOG.rst#3180-2022-09-15
+from marshmallow import __version__ as _MarshmallowVersion
+# the package "packaging" is a requirement of marshmallow itself => we don't need to install it separately
+# see https://github.com/marshmallow-code/marshmallow/blob/ddbe06f923befe754e213e03fb95be54e996403d/setup.py#L61
+from packaging.version import Version
+
+
+def marshmallow_version_supports_native_enums() -> bool:
+    """
+    returns true if and only if the version of marshmallow installed supports enums natively
+    """
+    return Version(_MarshmallowVersion) >= Version("3.18")
+
 
 try:
     from marshmallow_union import Union
@@ -20,11 +33,15 @@
     ALLOW_UNIONS = False
 
 try:
-    from marshmallow_enum import EnumField, LoadDumpOptions
+    from marshmallow_enum import EnumField as MarshmallowEnumEnumField, LoadDumpOptions
 
-    ALLOW_ENUMS = True
+    ALLOW_MARSHMALLOW_ENUM_ENUMS = True
 except ImportError:
-    ALLOW_ENUMS = False
+    ALLOW_MARSHMALLOW_ENUM_ENUMS = False
+
+ALLOW_MARSHMALLOW_NATIVE_ENUMS = marshmallow_version_supports_native_enums()
+if ALLOW_MARSHMALLOW_NATIVE_ENUMS:
+    from marshmallow.fields import Enum as MarshmallowNativeEnumField
 
 from .exceptions import UnsupportedValueError
 from .validation import (
@@ -92,10 +109,12 @@
     (fields.Nested, dict),
 ]
 
-if ALLOW_ENUMS:
+if ALLOW_MARSHMALLOW_NATIVE_ENUMS:
+    MARSHMALLOW_TO_PY_TYPES_PAIRS.append((MarshmallowNativeEnumField, Enum))
+if ALLOW_MARSHMALLOW_ENUM_ENUMS:
     # We currently only support loading enum's from their names. So the possible
     # values will always map to string in the JSONSchema
-    MARSHMALLOW_TO_PY_TYPES_PAIRS.append((EnumField, Enum))
+    MARSHMALLOW_TO_PY_TYPES_PAIRS.append((MarshmallowEnumEnumField, Enum))
 
 
 FIELD_VALIDATORS = {
@@ -191,8 +210,10 @@ def _from_python_type(self, obj, field, pytype) -> typing.Dict[str, typing.Any]:
         if field.default is not missing and not callable(field.default):
             json_schema["default"] = field.default
 
-        if ALLOW_ENUMS and isinstance(field, EnumField):
-            json_schema["enum"] = self._get_enum_values(field)
+        if ALLOW_MARSHMALLOW_NATIVE_ENUMS and isinstance(field, MarshmallowNativeEnumField):
+            json_schema["enum"] = self._get_marshmallow_native_enum_values(field)
+        elif ALLOW_MARSHMALLOW_ENUM_ENUMS and isinstance(field, MarshmallowEnumEnumField):
+            json_schema["enum"] = self._get_marshmallow_enum_enum_values(field)
 
         if field.allow_none:
             previous_type = json_schema["type"]
@@ -218,8 +239,8 @@ def _from_python_type(self, obj, field, pytype) -> typing.Dict[str, typing.Any]:
             )
         return json_schema
 
-    def _get_enum_values(self, field) -> typing.List[str]:
-        assert ALLOW_ENUMS and isinstance(field, EnumField)
+    def _get_marshmallow_enum_enum_values(self, field) -> typing.List[str]:
+        assert ALLOW_MARSHMALLOW_ENUM_ENUMS and isinstance(field, MarshmallowEnumEnumField)
 
         if field.load_by == LoadDumpOptions.value:
             # Python allows enum values to be almost anything, so it's easier to just load from the
@@ -229,6 +250,17 @@ def _get_enum_values(self, field) -> typing.List[str]:
             )
 
         return [value.name for value in field.enum]
+    def _get_marshmallow_native_enum_values(self, field) -> typing.List[str]:
+        assert ALLOW_MARSHMALLOW_NATIVE_ENUMS and isinstance(field, MarshmallowNativeEnumField)
+
+        if field.by_value:
+            # Python allows enum values to be almost anything, so it's easier to just load from the
+            # names of the enum's which will have to be strings.
+            raise NotImplementedError(
+                "Currently do not support JSON schema for enums loaded by value"
+            )
+
+        return [value.name for value in field.enum]
 
     def _from_union_schema(
         self, obj, field

tests/test_dump.py

@@ -3,12 +3,18 @@
 
 import pytest
 from marshmallow import Schema, fields, validate
-from marshmallow_enum import EnumField
+from marshmallow_enum import EnumField as MarshmallowEnumEnumField
 from marshmallow_union import Union
 
+import marshmallow_jsonschema
 from marshmallow_jsonschema import JSONSchema, UnsupportedValueError
 from . import UserSchema, validate_and_dump
 
+TEST_MARSHMALLOW_NATIVE_ENUM = marshmallow_jsonschema.base.marshmallow_version_supports_native_enums()
+try:
+    from marshmallow.fields import Enum as MarshmallowNativeEnumField
+except ImportError:
+    assert TEST_MARSHMALLOW_NATIVE_ENUM is False
 
 def test_dump_schema():
     schema = UserSchema()
@@ -648,14 +654,14 @@ class Meta:
     assert properties_names == ["d", "c", "a"]
 
 
-def test_enum_based():
+def test_marshmallow_enum_enum_based():
     class TestEnum(Enum):
         value_1 = 0
         value_2 = 1
         value_3 = 2
 
     class TestSchema(Schema):
-        enum_prop = EnumField(TestEnum)
+        enum_prop = MarshmallowEnumEnumField(TestEnum)
 
     # Should be sorting of fields
     schema = TestSchema()
@@ -671,15 +677,39 @@ class TestSchema(Schema):
     )
     assert received_enum_values == ["value_1", "value_2", "value_3"]
 
+def test_native_marshmallow_enum_based():
+    if not TEST_MARSHMALLOW_NATIVE_ENUM:
+        return
+    class TestEnum(Enum):
+        value_1 = 0
+        value_2 = 1
+        value_3 = 2
+
+    class TestSchema(Schema):
+        enum_prop = MarshmallowNativeEnumField(TestEnum)
+
+    # Should be sorting of fields
+    schema = TestSchema()
+
+    json_schema = JSONSchema()
+    data = json_schema.dump(schema)
+
+    assert (
+        data["definitions"]["TestSchema"]["properties"]["enum_prop"]["type"] == "string"
+    )
+    received_enum_values = sorted(
+        data["definitions"]["TestSchema"]["properties"]["enum_prop"]["enum"]
+    )
+    assert received_enum_values == ["value_1", "value_2", "value_3"]
 
-def test_enum_based_load_dump_value():
+def test_marshmallow_enum_enum_based_load_dump_value():
     class TestEnum(Enum):
         value_1 = 0
         value_2 = 1
         value_3 = 2
 
     class TestSchema(Schema):
-        enum_prop = EnumField(TestEnum, by_value=True)
+        enum_prop = MarshmallowEnumEnumField(TestEnum, by_value=True)
 
     # Should be sorting of fields
     schema = TestSchema()
@@ -689,6 +719,24 @@ class TestSchema(Schema):
     with pytest.raises(NotImplementedError):
         validate_and_dump(json_schema.dump(schema))
 
+def test_native_marshmallow_enum_based_load_dump_value():
+    if not TEST_MARSHMALLOW_NATIVE_ENUM:
+        return
+    class TestEnum(Enum):
+        value_1 = 0
+        value_2 = 1
+        value_3 = 2
+
+    class TestSchema(Schema):
+        enum_prop = MarshmallowNativeEnumField(TestEnum, by_value=True)
+
+    # Should be sorting of fields
+    schema = TestSchema()
+
+    json_schema = JSONSchema()
+
+    with pytest.raises(NotImplementedError):
+        validate_and_dump(json_schema.dump(schema))
 
 def test_union_based():
     class TestNestedSchema(Schema):

tests/test_imports.py

@@ -19,7 +19,7 @@ def test_import_marshmallow_enum(monkeypatch):
 
     base = importlib.reload(marshmallow_jsonschema.base)
 
-    assert not base.ALLOW_ENUMS
+    assert not base.ALLOW_MARSHMALLOW_ENUM_ENUMS
 
     monkeypatch.undo()