Fix recursive TypeAlias generation for Python 3.11 (covers mutual alias refs) (#2570)

* fix: enhance recursive type alias handling for Python 3.11

* fix: improve handling of recursive type aliases and render order

* fix: skip tests for mutual recursive type aliases on unsupported black versions

* fix: enhance type alias handling for recursive and cross-module scenarios

* fix: simplify type hint rendering and improve type alias handling

* fix: remove redundant test for TypeAlias with no fields

* fix: refine type alias handling in recursive type resolution

* fix: update type alias definitions for improved compatibility with Python 3.11

* fix: update type alias handling to properly manage forward references per PEP 484

Author: koxudaxi

src/datamodel_code_generator/model/type_alias.py

@@ -59,7 +59,11 @@ class TypeAliasTypeBackport(TypeAliasBase):
 
 
 class TypeStatement(TypeAliasBase):
-    """Type statement for Python 3.12+ (type Name = type)."""
+    """Type statement for Python 3.12+ (type Name = type).
+
+    Note: Python 3.12+ type statements use deferred evaluation,
+    so forward references don't need to be quoted.
+    """
 
     TEMPLATE_FILE_PATH: ClassVar[str] = "TypeStatement.jinja2"
     BASE_CLASS: ClassVar[str] = ""

src/datamodel_code_generator/parser/base.py

@@ -47,7 +47,7 @@
     DataModelFieldBase,
 )
 from datamodel_code_generator.model.enum import Enum, Member
-from datamodel_code_generator.model.type_alias import TypeAliasBase
+from datamodel_code_generator.model.type_alias import TypeAliasBase, TypeStatement
 from datamodel_code_generator.parser import DefaultPutDict, LiteralType
 from datamodel_code_generator.reference import ModelResolver, Reference
 from datamodel_code_generator.types import DataType, DataTypeManager, StrictTypes
@@ -1298,6 +1298,34 @@ def __set_one_literal_on_default(self, models: list[DataModel]) -> None:
                 if model_field.nullable is not True:  # pragma: no cover
                     model_field.nullable = False
 
+    @classmethod
+    def __update_type_aliases(cls, models: list[DataModel]) -> None:
+        """Update type aliases to properly handle forward references per PEP 484."""
+        rendered_aliases: set[str] = set()
+
+        for model in models:
+            if not isinstance(model, TypeAliasBase):
+                continue
+
+            if isinstance(model, TypeStatement):
+                rendered_aliases.add(model.class_name)
+                continue
+
+            for field in model.fields:
+                for data_type in field.data_type.all_data_types:
+                    if not data_type.reference:
+                        continue
+                    source = data_type.reference.source
+                    if not isinstance(source, TypeAliasBase):
+                        continue
+                    if isinstance(source, TypeStatement):  # pragma: no cover
+                        continue
+                    name = data_type.reference.short_name
+                    if name not in rendered_aliases:
+                        data_type.alias = f'"{name}"'
+
+            rendered_aliases.add(model.class_name)
+
     @classmethod
     def __postprocess_result_modules(cls, results: dict[tuple[str, ...], Result]) -> dict[tuple[str, ...], Result]:
         def process(input_tuple: tuple[str, ...]) -> tuple[str, ...]:
@@ -1547,6 +1575,7 @@ class Processed(NamedTuple):
                 if with_import:
                     result += [str(self.imports), str(imports), "\n"]
 
+                self.__update_type_aliases(models)
                 code = dump_templates(models)
                 result += [code]
 

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

@@ -0,0 +1,12 @@
+# generated by datamodel-codegen:
+#   filename:  type_alias_mutual_recursive.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import TypeAlias, Union
+
+NodeA: TypeAlias = Union[int, "NodeB"]
+
+
+NodeB: TypeAlias = Union[str, NodeA]

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

@@ -0,0 +1,9 @@
+# generated by datamodel-codegen:
+#   filename:  a.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import TypeAlias
+
+Item: TypeAlias = str

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

@@ -0,0 +1,9 @@
+# generated by datamodel-codegen:
+#   filename:  b.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List, TypeAlias
+
+Item: TypeAlias = List["Item"]

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

@@ -0,0 +1,22 @@
+# generated by datamodel-codegen:
+#   filename:  type_alias_forward_ref_multiple.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional, TypeAlias, Union
+
+from pydantic import BaseModel
+
+
+class RegularModel(BaseModel):
+    name: Optional[str] = None
+
+
+Third: TypeAlias = str
+
+
+Second: TypeAlias = Union["First", Third, RegularModel]
+
+
+First: TypeAlias = Second

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

@@ -0,0 +1,12 @@
+# generated by datamodel-codegen:
+#   filename:  type_alias_mutual_recursive.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import TypeAlias, Union
+
+NodeA: TypeAlias = Union[int, "NodeB"]
+
+
+NodeB: TypeAlias = Union[str, NodeA]

tests/data/expected/main/openapi/type_alias_recursive_py311.py

@@ -0,0 +1,41 @@
+# generated by datamodel-codegen:
+#   filename:  type_alias_recursive.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Dict, List, Optional, TypeAlias, Union
+
+from pydantic import BaseModel
+
+
+class File(BaseModel):
+    path: str
+
+
+class Folder(BaseModel):
+    address: Optional[str] = None
+    files: List[File]
+    subfolders: Optional[List[Folder]] = None
+
+
+ElementaryType: TypeAlias = Optional[Union[bool, str, int, float]]
+
+
+JsonType: TypeAlias = Union[ElementaryType, List["JsonType"], Dict[str, "JsonType"]]
+
+
+class Space(BaseModel):
+    label: Optional[str] = None
+    data: Optional[JsonType] = None
+    dual: Optional[DualSpace] = None
+
+
+class DualSpace(BaseModel):
+    label: Optional[str] = None
+    data: Optional[JsonType] = None
+    predual: Optional[Space] = None
+
+
+Folder.update_forward_refs()
+Space.update_forward_refs()

tests/data/openapi/type_alias_cross_module_collision/a.yaml

@@ -0,0 +1,8 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Module A
+components:
+  schemas:
+    Item:
+      type: string

tests/data/openapi/type_alias_cross_module_collision/b.yaml

@@ -0,0 +1,11 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Module B
+components:
+  schemas:
+    Item:
+      oneOf:
+        - type: array
+          items:
+            $ref: "#/components/schemas/Item"