Fix allOf array items partial override to inherit parent item types instead of Any (#2667)

* Fix allOf array item type inheritance for partial overrides

* Add test for OpenAPI allOf partial override with List[Any] and update related files

* Fix type inheritance for nested array items in allOf partial overrides

Author: koxudaxi

src/datamodel_code_generator/parser/jsonschema.py

@@ -1344,6 +1344,27 @@ def _build_lightweight_type(  # noqa: PLR0911, PLR0912
 
         return None
 
+    def _is_list_with_any_item_type(self, data_type: DataType | None) -> bool:  # noqa: PLR6301
+        """Return True when data_type represents List[Any] (including nested lists)."""
+        if not data_type:  # pragma: no cover
+            return False
+
+        candidate = data_type
+        if not candidate.is_list and len(candidate.data_types) == 1 and candidate.data_types[0].is_list:
+            candidate = candidate.data_types[0]
+
+        if not candidate.is_list or len(candidate.data_types) != 1:
+            return False
+
+        item_type = candidate.data_types[0]
+        while len(item_type.data_types) == 1:
+            inner = item_type.data_types[0]
+            if (not item_type.is_list and inner.is_list) or item_type.is_list:
+                item_type = inner
+            else:
+                break
+        return item_type.type == ANY
+
     def _get_inherited_field_type(self, prop_name: str, base_classes: list[Reference]) -> DataType | None:
         """Get the data type for an inherited property from parent schemas."""
         for base in base_classes:
@@ -1497,7 +1518,7 @@ def _create_data_model(self, model_type: type[DataModel] | None = None, **kwargs
             kwargs.pop("dataclass_arguments", None)
         return data_model_class(**kwargs)
 
-    def _parse_object_common_part(  # noqa: PLR0912, PLR0913
+    def _parse_object_common_part(  # noqa: PLR0912, PLR0913, PLR0915
         self,
         name: str,
         obj: JsonSchemaObject,
@@ -1539,6 +1560,37 @@ def _parse_object_common_part(  # noqa: PLR0912, PLR0913
                         if new_type.kwargs is None and current_type.kwargs is not None:  # pragma: no cover
                             new_type.kwargs = current_type.kwargs
                         field.data_type = new_type
+                # Handle List[Any] case: inherit item type from parent if items have Any type
+                elif field_name and self._is_list_with_any_item_type(current_type):
+                    inherited_type = self._get_inherited_field_type(field_name, base_classes)
+                    if inherited_type is None or not inherited_type.is_list or not inherited_type.data_types:
+                        continue
+
+                    new_type = inherited_type.model_copy(deep=True) if PYDANTIC_V2 else inherited_type.copy(deep=True)
+
+                    # Preserve modifiers coming from the overriding schema.
+                    if current_type is not None:  # pragma: no branch
+                        new_type.is_optional = new_type.is_optional or current_type.is_optional
+                        new_type.is_dict = new_type.is_dict or current_type.is_dict
+                        new_type.is_list = new_type.is_list or current_type.is_list
+                        new_type.is_set = new_type.is_set or current_type.is_set
+                        if new_type.kwargs is None and current_type.kwargs is not None:  # pragma: no cover
+                            new_type.kwargs = current_type.kwargs
+
+                    # Some code paths represent the list type inside an outer container.
+                    is_wrapped = (
+                        current_type is not None
+                        and not current_type.is_list
+                        and len(current_type.data_types) == 1
+                        and current_type.data_types[0].is_list
+                    )
+                    if is_wrapped:
+                        wrapper = current_type.model_copy(deep=True) if PYDANTIC_V2 else current_type.copy(deep=True)
+                        wrapper.data_types[0] = new_type
+                        field.data_type = wrapper
+                        continue
+
+                    field.data_type = new_type  # pragma: no cover
         # ignore an undetected object
         if ignore_duplicate_model and not fields and len(base_classes) == 1:
             with self.model_resolver.current_base_path_context(self.model_resolver._base_path):  # noqa: SLF001

tests/data/expected/main/openapi/allof_partial_override_array_items.py

@@ -0,0 +1,19 @@
+# generated by datamodel-codegen:
+#   filename:  allof_partial_override_array_items.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List, Optional
+
+from pydantic import BaseModel
+
+
+class Thing(BaseModel):
+    type: Optional[str] = 'playground:Thing'
+    type_list: Optional[List[str]] = ['playground:Thing']
+
+
+class Person(Thing):
+    type: Optional[str] = 'playground:Person'
+    type_list: Optional[List[str]] = ['playground:Person']

tests/data/expected/main/openapi/allof_partial_override_array_items_no_parent.py

@@ -0,0 +1,17 @@
+# generated by datamodel-codegen:
+#   filename:  allof_partial_override_array_items_no_parent.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Any, List, Optional
+
+from pydantic import BaseModel
+
+
+class Thing(BaseModel):
+    name: Optional[str] = None
+
+
+class Person(Thing):
+    tags: Optional[List[Any]] = ['tag1']

tests/data/expected/main/openapi/allof_partial_override_deeply_nested_array.py

@@ -0,0 +1,17 @@
+# generated by datamodel-codegen:
+#   filename:  allof_partial_override_deeply_nested_array.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List, Optional
+
+from pydantic import BaseModel
+
+
+class Thing(BaseModel):
+    cube: Optional[List[List[List[str]]]] = [[['a']]]
+
+
+class Person(Thing):
+    cube: Optional[List[List[List[str]]]] = [[['b']]]

tests/data/expected/main/openapi/allof_partial_override_nested_array_items.py

@@ -0,0 +1,17 @@
+# generated by datamodel-codegen:
+#   filename:  allof_partial_override_nested_array_items.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List, Optional
+
+from pydantic import BaseModel
+
+
+class Thing(BaseModel):
+    matrix: Optional[List[List[str]]] = [['a', 'b']]
+
+
+class Person(Thing):
+    matrix: Optional[List[List[str]]] = [['c', 'd']]

tests/data/expected/main/openapi/allof_partial_override_non_array_field.py

@@ -0,0 +1,19 @@
+# generated by datamodel-codegen:
+#   filename:  allof_partial_override_non_array_field.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+
+class Thing(BaseModel):
+    name: Optional[str] = 'default_name'
+    count: Optional[int] = 0
+
+
+class Person(Thing):
+    name: Optional[str] = Field(None, title='Person name')
+    count: Optional[int] = Field(None, description='Count value')

tests/data/expected/main/openapi/allof_partial_override_simple_list_any.py

@@ -0,0 +1,17 @@
+# generated by datamodel-codegen:
+#   filename:  allof_partial_override_simple_list_any.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List, Optional
+
+from pydantic import BaseModel
+
+
+class Parent(BaseModel):
+    items: Optional[List[str]] = None
+
+
+class Child(Parent):
+    items: Optional[List[str]] = None

tests/data/openapi/allof_partial_override_array_items.yaml

@@ -0,0 +1,27 @@
+openapi: "3.0.0"
+components:
+  schemas:
+    Thing:
+      type: object
+      properties:
+        type:
+          type: string
+          default: playground:Thing
+        type_list:
+          type: array
+          default:
+            - playground:Thing
+          items:
+            type: string
+    Person:
+      allOf:
+        - $ref: "#/components/schemas/Thing"
+        - type: object
+          properties:
+            type:
+              default: playground:Person
+            type_list:
+              default:
+                - playground:Person
+              items:
+                title: A type entry

tests/data/openapi/allof_partial_override_array_items_no_parent.yaml

@@ -0,0 +1,19 @@
+openapi: "3.0.0"
+components:
+  schemas:
+    Thing:
+      type: object
+      properties:
+        name:
+          type: string
+    Person:
+      allOf:
+        - $ref: "#/components/schemas/Thing"
+        - type: object
+          properties:
+            tags:
+              type: array
+              default:
+                - tag1
+              items:
+                title: A tag entry

tests/data/openapi/allof_partial_override_deeply_nested_array.yaml

@@ -0,0 +1,30 @@
+openapi: "3.0.0"
+components:
+  schemas:
+    Thing:
+      type: object
+      properties:
+        cube:
+          type: array
+          default:
+            - - - a
+          items:
+            type: array
+            items:
+              type: array
+              items:
+                type: string
+    Person:
+      allOf:
+        - $ref: "#/components/schemas/Thing"
+        - type: object
+          properties:
+            cube:
+              default:
+                - - - b
+              items:
+                title: A plane
+                items:
+                  title: A row
+                  items:
+                    title: A cell