Add ability to specify dataclass name in dataclass_schema

Author: dmontagu

pydantic_core/core_schema.py

@@ -3111,6 +3111,7 @@ class DataclassSchema(TypedDict, total=False):
     type: Required[Literal['dataclass']]
     cls: Required[Type[Any]]
     schema: Required[CoreSchema]
+    cls_name: str
     post_init: bool  # default: False
     revalidate_instances: Literal['always', 'never', 'subclass-instances']  # default: 'never'
     strict: bool  # default: False
@@ -3124,6 +3125,7 @@ def dataclass_schema(
     cls: Type[Any],
     schema: CoreSchema,
     *,
+    cls_name: str | None = None,
     post_init: bool | None = None,
     revalidate_instances: Literal['always', 'never', 'subclass-instances'] | None = None,
     strict: bool | None = None,
@@ -3139,6 +3141,7 @@ def dataclass_schema(
     Args:
         cls: The dataclass type, used to to perform subclass checks
         schema: The schema to use for the dataclass fields
+        cls_name: The name to use for the class in error locs, etc; this is useful for generics (default: cls.__name__)
         post_init: Whether to call `__post_init__` after validation
         revalidate_instances: whether instances of models and dataclasses (including subclass instances)
             should re-validate defaults to config.revalidate_instances, else 'never'
@@ -3151,6 +3154,7 @@ def dataclass_schema(
     return dict_not_none(
         type='dataclass',
         cls=cls,
+        cls_name=cls_name,
         schema=schema,
         post_init=post_init,
         revalidate_instances=revalidate_instances,

src/validators/dataclass.rs

@@ -428,6 +428,10 @@ impl BuildValidator for DataclassValidator {
         let py = schema.py();
 
         let class: &PyType = schema.get_as_req(intern!(py, "cls"))?;
+        let name = match schema.get_as_req::<String>(intern!(py, "cls_name")) {
+            Ok(name) => name,
+            Err(_) => class.getattr(intern!(py, "__name__"))?.extract()?,
+        };
         let sub_schema: &PyAny = schema.get_as_req(intern!(py, "schema"))?;
         let validator = build_validator(sub_schema, config, definitions)?;
 
@@ -447,9 +451,7 @@ impl BuildValidator for DataclassValidator {
                 config,
                 intern!(py, "revalidate_instances"),
             )?)?,
-            // as with model, get the class's `__name__`, not using `class.name()` since it uses `__qualname__`
-            // which is not what we want here
-            name: class.getattr(intern!(py, "__name__"))?.extract()?,
+            name,
             frozen: schema.get_as(intern!(py, "frozen"))?.unwrap_or(false),
         }
         .into())

tests/validators/test_dataclasses.py

@@ -1,6 +1,6 @@
 import dataclasses
 import re
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, List, Optional, Union
 
 import pytest
 from dirty_equals import IsListOrTuple, IsStr
@@ -1137,3 +1137,56 @@ class Model:
     v.validate_assignment(instance, 'number', 2)
     assert instance.number == 2
     assert calls == [({'number': 1}, ({'number': 1}, None)), ({'number': 2}, ({'number': 2}, None))]
+
+
+@dataclasses.dataclass
+class FooParentDataclass:
+    foo: Optional[FooDataclass]
+
+
+def test_custom_dataclass_names():
+    # Note: normally you would use the same values for DataclassArgsSchema.dataclass_name and DataclassSchema.cls_name,
+    # but I have purposely made them different here to show which parts of the errors are affected by which.
+    # I have used square brackets in the names to hint that the most likely reason for using a value different from
+    # cls.__name__ is for use with generic types.
+    schema = core_schema.dataclass_schema(
+        FooParentDataclass,
+        core_schema.dataclass_args_schema(
+            'FooParentDataclass',
+            [
+                core_schema.dataclass_field(
+                    name='foo',
+                    schema=core_schema.union_schema(
+                        [
+                            core_schema.dataclass_schema(
+                                FooDataclass,
+                                core_schema.dataclass_args_schema(
+                                    'FooDataclass[dataclass_args_schema]',
+                                    [
+                                        core_schema.dataclass_field(name='a', schema=core_schema.str_schema()),
+                                        core_schema.dataclass_field(name='b', schema=core_schema.bool_schema()),
+                                    ],
+                                ),
+                                cls_name='FooDataclass[cls_name]',
+                            ),
+                            core_schema.none_schema(),
+                        ]
+                    ),
+                )
+            ],
+        ),
+    )
+
+    v = SchemaValidator(schema)
+    with pytest.raises(ValidationError) as exc_info:
+        v.validate_python({'foo': 123})
+    assert exc_info.value.errors(include_url=False) == [
+        {
+            'ctx': {'dataclass_name': 'FooDataclass[dataclass_args_schema]'},
+            'input': 123,
+            'loc': ('foo', 'FooDataclass[cls_name]'),
+            'msg': 'Input should be a dictionary or an instance of FooDataclass[dataclass_args_schema]',
+            'type': 'dataclass_type',
+        },
+        {'input': 123, 'loc': ('foo', 'none'), 'msg': 'Input should be None', 'type': 'none_required'},
+    ]