Discriminated union schemas use oneOf instead of anyOf (#4335)

pydantic · Aug 11, 2022 · 4cb58cf · 4cb58cf
1 parent 149c05b
commit 4cb58cf
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Showing 5 changed files with 18 additions and 16 deletions.
diff --git a/changes/4335-MaxwellPayne.md b/changes/4335-MaxwellPayne.md
@@ -0,0 +1 @@
+Discriminated union models now use `oneOf` instead of `anyOf` when generating OpenAPI schema definitions.
diff --git a/pydantic/schema.py b/pydantic/schema.py
@@ -705,7 +705,8 @@ def field_singleton_sub_fields_schema(
     else:
         s: Dict[str, Any] = {}
         # https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#discriminator-object
-        if field.discriminator_key is not None:
+        field_has_discriminator: bool = field.discriminator_key is not None
+        if field_has_discriminator:
             assert field.sub_fields_mapping is not None
 
             discriminator_models_refs: Dict[str, Union[str, Dict[str, Any]]] = {}
@@ -748,16 +749,16 @@ def field_singleton_sub_fields_schema(
             definitions.update(sub_definitions)
             if schema_overrides and 'allOf' in sub_schema:
                 # if the sub_field is a referenced schema we only need the referenced
-                # object. Otherwise we will end up with several allOf inside anyOf.
+                # object. Otherwise we will end up with several allOf inside anyOf/oneOf.
                 # See https://github.com/pydantic/pydantic/issues/1209
                 sub_schema = sub_schema['allOf'][0]
 
-            if sub_schema.keys() == {'discriminator', 'anyOf'}:
-                # we don't want discriminator information inside anyOf choices, this is dealt with elsewhere
+            if sub_schema.keys() == {'discriminator', 'oneOf'}:
+                # we don't want discriminator information inside oneOf choices, this is dealt with elsewhere
                 sub_schema.pop('discriminator')
             sub_field_schemas.append(sub_schema)
             nested_models.update(sub_nested_models)
-        s['anyOf'] = sub_field_schemas
+        s['oneOf' if field_has_discriminator else 'anyOf'] = sub_field_schemas
         return s, definitions, nested_models
 
 

diff --git a/tests/test_dataclasses.py b/tests/test_dataclasses.py
@@ -1201,7 +1201,7 @@ class Users(BaseModel):
     }
 
 
-def test_discrimated_union_basemodel_instance_value():
+def test_discriminated_union_basemodel_instance_value():
     @pydantic.dataclasses.dataclass
     class A:
         l: Literal['a']
@@ -1223,7 +1223,7 @@ class Top:
             'sub': {
                 'title': 'Sub',
                 'discriminator': {'propertyName': 'l', 'mapping': {'a': '#/definitions/A', 'b': '#/definitions/B'}},
-                'anyOf': [{'$ref': '#/definitions/A'}, {'$ref': '#/definitions/B'}],
+                'oneOf': [{'$ref': '#/definitions/A'}, {'$ref': '#/definitions/B'}],
             }
         },
         'required': ['sub'],

diff --git a/tests/test_forward_ref.py b/tests/test_forward_ref.py
@@ -588,7 +588,7 @@ class Dog(BaseModel):
     assert module.Pet.schema() == {
         'title': 'Pet',
         'discriminator': {'propertyName': 'type', 'mapping': {'cat': '#/definitions/Cat', 'dog': '#/definitions/Dog'}},
-        'anyOf': [{'$ref': '#/definitions/Cat'}, {'$ref': '#/definitions/Dog'}],
+        'oneOf': [{'$ref': '#/definitions/Cat'}, {'$ref': '#/definitions/Dog'}],
         'definitions': {
             'Cat': {
                 'title': 'Cat',

diff --git a/tests/test_schema.py b/tests/test_schema.py
@@ -2675,7 +2675,7 @@ class Model(BaseModel):
                         'lizard': '#/definitions/Lizard',
                     },
                 },
-                'anyOf': [
+                'oneOf': [
                     {'$ref': '#/definitions/Cat'},
                     {'$ref': '#/definitions/Dog'},
                     {'$ref': '#/definitions/Lizard'},
@@ -2708,7 +2708,7 @@ class Model(BaseModel):
                     'propertyName': 'color',
                     'mapping': {'black': '#/definitions/BlackCat', 'white': '#/definitions/WhiteCat'},
                 },
-                'anyOf': [{'$ref': '#/definitions/BlackCat'}, {'$ref': '#/definitions/WhiteCat'}],
+                'oneOf': [{'$ref': '#/definitions/BlackCat'}, {'$ref': '#/definitions/WhiteCat'}],
             },
             'Dog': {
                 'title': 'Dog',
@@ -2775,11 +2775,11 @@ class Model(BaseModel):
                         'dog': '#/definitions/Dog',
                     },
                 },
-                'anyOf': [
+                'oneOf': [
                     {
-                        'anyOf': [
+                        'oneOf': [
                             {
-                                'anyOf': [
+                                'oneOf': [
                                     {'$ref': '#/definitions/BlackCatWithHeight'},
                                     {'$ref': '#/definitions/BlackCatWithWeight'},
                                 ]
@@ -2858,7 +2858,7 @@ class Model(BaseModel):
         'properties': {
             'number': {'title': 'Number', 'type': 'integer'},
             'pet': {
-                'anyOf': [{'$ref': '#/definitions/Cat'}, {'$ref': '#/definitions/Dog'}],
+                'oneOf': [{'$ref': '#/definitions/Cat'}, {'$ref': '#/definitions/Dog'}],
                 'discriminator': {
                     'mapping': {'cat': '#/definitions/Cat', 'dog': '#/definitions/Dog'},
                     'propertyName': 'typeOfPet',
@@ -2960,9 +2960,9 @@ class Model(BaseModel):
                         'dog': '#/definitions/Dog',
                     },
                 },
-                'anyOf': [
+                'oneOf': [
                     {
-                        'anyOf': [
+                        'oneOf': [
                             {'$ref': '#/definitions/BlackCat'},
                             {'$ref': '#/definitions/WhiteCat'},
                         ],