feat(schema): set minItems and maxItems in JSON schema for tuples (…

…#2497) * feat(schema): enforce length in generated JSON schema for tuple type * docs: add change file * docs: update documentation * simplify a bit * always set array
pydantic · Dec 5, 2021 · a35cde9 · a35cde9
1 parent cc1cb48
commit a35cde9
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Showing 5 changed files with 66 additions and 26 deletions.
diff --git a/changes/2497-PrettyWood.md b/changes/2497-PrettyWood.md
@@ -0,0 +1 @@
+Set `minItems` and `maxItems` in generated JSON schema for fixed-length tuples
diff --git a/docs/build/schema_mapping.py b/docs/build/schema_mapping.py
@@ -81,10 +81,17 @@
         'JSON Schema Validation',
         'And equivalently for any other sub type, e.g. `List[int]`.'
     ],
+    [
+        'Tuple[str, ...]',
+        'array',
+        {'items': {'type': 'string'}},
+        'JSON Schema Validation',
+        'And equivalently for any other sub type, e.g. `Tuple[int, ...]`.'
+    ],
     [
         'Tuple[str, int]',
         'array',
-        {'items': [{'type': 'string'}, {'type': 'integer'}]},
+        {'items': [{'type': 'string'}, {'type': 'integer'}], 'minItems': 2, 'maxItems': 2},
         'JSON Schema Validation',
         (
             'And equivalently for any other set of subtypes. Note: If using schemas for OpenAPI, '

diff --git a/pydantic/schema.py b/pydantic/schema.py
@@ -499,15 +499,19 @@ def field_type_schema(
             definitions.update(sf_definitions)
             nested_models.update(sf_nested_models)
             sub_schema.append(sf_schema)
-        if len(sub_schema) == 1:
-            if field.shape == SHAPE_GENERIC:
-                f_schema = sub_schema[0]
-            else:
-                f_schema = {'type': 'array', 'items': sub_schema[0]}
-        else:
-            f_schema = {'type': 'array', 'items': sub_schema}
+
+        sub_fields_len = len(sub_fields)
         if field.shape == SHAPE_GENERIC:
-            f_schema = {'allOf': [f_schema]}
+            all_of_schemas = sub_schema[0] if sub_fields_len == 1 else {'type': 'array', 'items': sub_schema}
+            f_schema = {'allOf': [all_of_schemas]}
+        else:
+            f_schema = {
+                'type': 'array',
+                'minItems': sub_fields_len,
+                'maxItems': sub_fields_len,
+            }
+            if sub_fields_len >= 1:
+                f_schema['items'] = sub_schema
     else:
         assert field.shape in {SHAPE_SINGLETON, SHAPE_GENERIC}, field.shape
         f_schema, f_definitions, f_nested_models = field_singleton_schema(
@@ -844,7 +848,15 @@ def field_singleton_schema(  # noqa: C901 (ignore complexity)
             ref_template=ref_template,
             known_models=known_models,
         )
-        f_schema.update({'type': 'array', 'items': list(sub_schema['properties'].values())})
+        items_schemas = list(sub_schema['properties'].values())
+        f_schema.update(
+            {
+                'type': 'array',
+                'items': items_schemas,
+                'minItems': len(items_schemas),
+                'maxItems': len(items_schemas),
+            }
+        )
     elif not hasattr(field_type, '__pydantic_model__'):
         add_field_type_to_schema(field_type, f_schema)
 

diff --git a/tests/test_annotated_types.py b/tests/test_annotated_types.py
@@ -79,6 +79,8 @@ class Model(BaseModel):
                     {'title': 'X', 'type': 'integer'},
                     {'title': 'Y', 'type': 'integer'},
                 ],
+                'minItems': 2,
+                'maxItems': 2,
             },
             'pos2': {
                 'title': 'Pos2',
@@ -87,6 +89,8 @@ class Model(BaseModel):
                     {'title': 'X'},
                     {'title': 'Y'},
                 ],
+                'minItems': 2,
+                'maxItems': 2,
             },
             'pos3': {
                 'title': 'Pos3',
@@ -95,6 +99,8 @@ class Model(BaseModel):
                     {'type': 'integer'},
                     {'type': 'integer'},
                 ],
+                'minItems': 2,
+                'maxItems': 2,
             },
         },
         'required': ['pos1', 'pos2', 'pos3'],

diff --git a/tests/test_schema.py b/tests/test_schema.py
@@ -535,34 +535,36 @@ class Model(BaseModel):
 
 
 @pytest.mark.parametrize(
-    'field_type,expected_schema',
+    'field_type,extra_props',
     [
-        (tuple, {}),
+        (tuple, {'items': {}}),
         (
             Tuple[str, int, Union[str, int, float], float],
-            [
-                {'type': 'string'},
-                {'type': 'integer'},
-                {'anyOf': [{'type': 'string'}, {'type': 'integer'}, {'type': 'number'}]},
-                {'type': 'number'},
-            ],
+            {
+                'items': [
+                    {'type': 'string'},
+                    {'type': 'integer'},
+                    {'anyOf': [{'type': 'string'}, {'type': 'integer'}, {'type': 'number'}]},
+                    {'type': 'number'},
+                ],
+                'minItems': 4,
+                'maxItems': 4,
+            },
         ),
-        (Tuple[str], {'type': 'string'}),
+        (Tuple[str], {'items': [{'type': 'string'}], 'minItems': 1, 'maxItems': 1}),
+        (Tuple[()], {'maxItems': 0, 'minItems': 0}),
     ],
 )
-def test_tuple(field_type, expected_schema):
+def test_tuple(field_type, extra_props):
     class Model(BaseModel):
         a: field_type
 
-    base_schema = {
+    assert Model.schema() == {
         'title': 'Model',
         'type': 'object',
-        'properties': {'a': {'title': 'A', 'type': 'array'}},
+        'properties': {'a': {'title': 'A', 'type': 'array', **extra_props}},
         'required': ['a'],
     }
-    base_schema['properties']['a']['items'] = expected_schema
-
-    assert Model.schema() == base_schema
 
 
 def test_deque():
@@ -1944,6 +1946,8 @@ class Config:
                     {'exclusiveMinimum': 0, 'type': 'integer'},
                     {'exclusiveMinimum': 0, 'type': 'integer'},
                 ],
+                'minItems': 3,
+                'maxItems': 3,
             },
         ),
         (
@@ -2333,6 +2337,8 @@ class LocationBase(BaseModel):
                 'default': Coordinates(x=0, y=0),
                 'type': 'array',
                 'items': [{'title': 'X', 'type': 'number'}, {'title': 'Y', 'type': 'number'}],
+                'minItems': 2,
+                'maxItems': 2,
             }
         },
     }
@@ -2424,11 +2430,19 @@ class Model(BaseModel):
                 'examples': 'examples',
             },
             'data3': {'title': 'Data3', 'type': 'array', 'items': {}},
-            'data4': {'title': 'Data4', 'type': 'array', 'items': {'$ref': '#/definitions/CustomType'}},
+            'data4': {
+                'title': 'Data4',
+                'type': 'array',
+                'items': [{'$ref': '#/definitions/CustomType'}],
+                'minItems': 1,
+                'maxItems': 1,
+            },
             'data5': {
                 'title': 'Data5',
                 'type': 'array',
                 'items': [{'$ref': '#/definitions/CustomType'}, {'type': 'string'}],
+                'minItems': 2,
+                'maxItems': 2,
             },
         },
         'required': ['data0', 'data1', 'data2', 'data3', 'data4', 'data5'],