Fix const validations

This fixes #620 and #793

changes/794-hmvp.rst

@@ -0,0 +1 @@
+Fix const validations for lists

pydantic/error_wrappers.py

@@ -105,7 +105,7 @@ def flatten_errors(
             else:
                 yield error.dict(config, loc_prefix=loc)
         elif isinstance(error, list):
-            yield from flatten_errors(error, config)
+            yield from flatten_errors(error, config, loc=loc)
         else:
             raise RuntimeError(f'Unknown error object: {error}')
 

pydantic/fields.py

@@ -106,8 +106,8 @@ def __init__(
         self.sub_fields: Optional[List[Field]] = None
         self.key_field: Optional[Field] = None
         self.validators: 'ValidatorsList' = []
-        self.whole_pre_validators: Optional['ValidatorsList'] = None
-        self.whole_post_validators: Optional['ValidatorsList'] = None
+        self.whole_pre_validators: 'ValidatorsList' = []
+        self.whole_post_validators: 'ValidatorsList' = []
         self.parse_json: bool = False
         self.shape: int = SHAPE_SINGLETON
         self.prepare()
@@ -251,9 +251,8 @@ def _populate_sub_fields(self) -> None:  # noqa: C901 (ignore complexity)
         else:
             raise TypeError(f'Fields of type "{origin}" are not supported.')
 
-        if getattr(self.type_, '__origin__', None):
-            # type_ has been refined eg. as the type of a List and sub_fields needs to be populated
-            self.sub_fields = [self._create_sub_type(self.type_, '_' + self.name)]
+        # type_ has been refined eg. as the type of a List and sub_fields needs to be populated
+        self.sub_fields = [self._create_sub_type(self.type_, '_' + self.name)]
 
     def _create_sub_type(self, type_: AnyType, name: str, *, for_keys: bool = False) -> 'Field':
         return self.__class__(
@@ -270,13 +269,16 @@ def _populate_validators(self) -> None:
             v_funcs = (
                 *[v.func for v in class_validators_ if not v.whole and v.pre],
                 *(get_validators() if get_validators else list(find_validators(self.type_, self.model_config))),
-                self.schema is not None and self.schema.const and constant_validator,
                 *[v.func for v in class_validators_ if not v.whole and not v.pre],
             )
             self.validators = self._prep_vals(v_funcs)
 
+        # Add const validator
+        if self.schema is not None and self.schema.const:
+            self.whole_pre_validators = self._prep_vals([constant_validator])
+
         if class_validators_:
-            self.whole_pre_validators = self._prep_vals(v.func for v in class_validators_ if v.whole and v.pre)
+            self.whole_pre_validators.extend(self._prep_vals(v.func for v in class_validators_ if v.whole and v.pre))
             self.whole_post_validators = self._prep_vals(v.func for v in class_validators_ if v.whole and not v.pre)
 
     @staticmethod

tests/test_main.py

@@ -1,3 +1,4 @@
+import json
 from enum import Enum
 from typing import Any, ClassVar, List, Mapping
 
@@ -397,6 +398,86 @@ class Model(BaseModel):
     ]
 
 
+def test_const_list():
+    class SubModel(BaseModel):
+        b: int
+
+    class Model(BaseModel):
+        a: List[SubModel] = Schema([SubModel(b=1), SubModel(b=2), SubModel(b=3)], const=True)
+        b: List[SubModel] = Schema([{'b': 4}, {'b': 5}, {'b': 6}], const=True)
+
+    m = Model()
+    assert m.a == [SubModel(b=1), SubModel(b=2), SubModel(b=3)]
+    assert m.b == [SubModel(b=4), SubModel(b=5), SubModel(b=6)]
+
+
+def test_const_list_with_wrong_value():
+    class SubModel(BaseModel):
+        b: int
+
+    class Model(BaseModel):
+        a: List[SubModel] = Schema([SubModel(b=1), SubModel(b=2), SubModel(b=3)], const=True)
+        b: List[SubModel] = Schema([{'b': 4}, {'b': 5}, {'b': 6}], const=True)
+
+    with pytest.raises(ValidationError) as exc_info:
+        Model(a=[{'b': 3}, {'b': 1}, {'b': 2}], b=[{'b': 6}, {'b': 5}])
+
+    assert exc_info.value.errors() == [
+        {
+            'ctx': {
+                'given': [{'b': 3}, {'b': 1}, {'b': 2}],
+                'permitted': [[SubModel(b=1), SubModel(b=2), SubModel(b=3)]],
+            },
+            'loc': ('a',),
+            'msg': 'unexpected value; permitted: [<SubModel b=1>, <SubModel b=2>, <SubModel b=3>]',
+            'type': 'value_error.const',
+        },
+        {
+            'ctx': {'given': [{'b': 6}, {'b': 5}], 'permitted': [[{'b': 4}, {'b': 5}, {'b': 6}]]},
+            'loc': ('b',),
+            'msg': "unexpected value; permitted: [{'b': 4}, {'b': 5}, {'b': 6}]",
+            'type': 'value_error.const',
+        },
+    ]
+
+    with pytest.raises(ValidationError) as exc_info:
+        Model(a=[SubModel(b=3), SubModel(b=1), SubModel(b=2)], b=[SubModel(b=3), SubModel(b=1)])
+
+    assert exc_info.value.errors() == [
+        {
+            'ctx': {
+                'given': [SubModel(b=3), SubModel(b=1), SubModel(b=2)],
+                'permitted': [[SubModel(b=1), SubModel(b=2), SubModel(b=3)]],
+            },
+            'loc': ('a',),
+            'msg': 'unexpected value; permitted: [<SubModel b=1>, <SubModel b=2>, <SubModel b=3>]',
+            'type': 'value_error.const',
+        },
+        {
+            'ctx': {'given': [SubModel(b=3), SubModel(b=1)], 'permitted': [[{'b': 4}, {'b': 5}, {'b': 6}]]},
+            'loc': ('b',),
+            'msg': "unexpected value; permitted: [{'b': 4}, {'b': 5}, {'b': 6}]",
+            'type': 'value_error.const',
+        },
+    ]
+
+
+def test_const_validation_json_serializable():
+    class SubForm(BaseModel):
+        field: int
+
+    class Form(BaseModel):
+        field1: SubForm = Schema({'field': 2}, const=True)
+        field2: List[SubForm] = Schema([{'field': 2}], const=True)
+
+    try:
+        # Fails
+        Form(field1={'field': 1}, field2=[{'field': 1}])
+    except ValidationError as e:
+        # This should not raise an Json error
+        assert json.dumps(e.json())
+
+
 class ValidateAssignmentModel(BaseModel):
     a: int = 2
     b: constr(min_length=1)