Fix handling of ClassVar fields in msgspec rendering to avoid conflicts (#2663)

Author: koxudaxi

src/datamodel_code_generator/model/msgspec.py

@@ -22,7 +22,6 @@
 from datamodel_code_generator.model import DataModel, DataModelFieldBase
 from datamodel_code_generator.model.base import UNDEFINED
 from datamodel_code_generator.model.imports import (
-    IMPORT_CLASSVAR,
     IMPORT_MSGSPEC_CONVERT,
     IMPORT_MSGSPEC_FIELD,
     IMPORT_MSGSPEC_META,
@@ -82,6 +81,8 @@ def import_extender(cls: type[DataModelFieldBaseT]) -> type[DataModelFieldBaseT]
 
     @wraps(original_imports.fget)  # pyright: ignore[reportArgumentType]
     def new_imports(self: DataModelFieldBaseT) -> tuple[Import, ...]:
+        if self.extras.get("is_classvar"):
+            return ()
         extra_imports = []
         field = self.field
         # TODO: Improve field detection
@@ -91,8 +92,6 @@ def new_imports(self: DataModelFieldBaseT) -> tuple[Import, ...]:
             extra_imports.append(IMPORT_MSGSPEC_CONVERT)
         if isinstance(self, DataModelField) and self.needs_meta_import:
             extra_imports.append(IMPORT_MSGSPEC_META)
-        if self.extras.get("is_classvar"):
-            extra_imports.append(IMPORT_CLASSVAR)
         if not self.required and not self.nullable:
             extra_imports.append(IMPORT_MSGSPEC_UNSETTYPE)
             if not self.data_type.use_union_operator:

src/datamodel_code_generator/model/template/msgspec.jinja2

@@ -13,13 +13,15 @@ class {{ class_name }}:
     {{ description | indent(4) }}
     """
 {%- endif %}
-{%- if not fields and not description %}
-    pass
-{%- endif %}
+{%- set ns = namespace(has_rendered_field=false) -%}
 {%- for field in fields -%}
-    {%- if not field.annotated and field.field %}
+    {%- if field.extras.get('is_classvar') %}
+    {#- Skip fields with is_classvar=True - they are managed by msgspec tag_field -#}
+    {%- elif not field.annotated and field.field %}
+    {%- set ns.has_rendered_field = true %}
     {{ field.name }}: {{ field.type_hint }} = {{ field.field }}
     {%- else %}
+    {%- set ns.has_rendered_field = true %}
     {%- if field.annotated and not field.field %}
     {{ field.name }}: {{ field.annotated }}
     {%- elif field.annotated and field.field %}
@@ -34,17 +36,20 @@ class {{ class_name }}:
 
 
 
-    {%- if field.docstring %}
+    {%- if not field.extras.get('is_classvar') and field.docstring %}
     """
     {{ field.docstring | indent(4) }}
     """
 {%- if field.use_inline_field_description and not loop.last %}
 
 {% endif %}
-    {%- elif field.inline_field_docstring %}
+    {%- elif not field.extras.get('is_classvar') and field.inline_field_docstring %}
     {{ field.inline_field_docstring }}
 {%- if not loop.last %}
 
 {% endif %}
     {%- endif %}
 {%- endfor -%}
+{%- if not ns.has_rendered_field and not description %}
+    pass
+{%- endif -%}

src/datamodel_code_generator/parser/base.py

@@ -2028,6 +2028,8 @@ def walk_data_type(data_type: DataType) -> None:
             for import_ in model.imports:
                 add(import_.alias or import_.import_.split(".")[-1])
             for field in model.fields:
+                if field.extras.get("is_classvar"):
+                    continue
                 add(field.name)
                 add(field.alias)
                 walk_data_type(field.data_type)
@@ -2495,7 +2497,9 @@ class Processed(NamedTuple):
                 )
             ]
             for from_, import_ in unused_imports:
-                processed_model.imports.remove(Import(from_=from_, import_=import_))
+                import_obj = Import(from_=from_, import_=import_)
+                while processed_model.imports.counter.get((from_, import_), 0) > 0:
+                    processed_model.imports.remove(import_obj)
 
         for module, mod_key, models, init, imports, scoped_model_resolver in processed_models:  # noqa: B007
             # process after removing unused models

tests/data/expected/main/jsonschema/discriminator_literals_msgspec.py

@@ -4,21 +4,17 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, Union
 
 from msgspec import Meta, Struct, UnsetType
 
 
 class Type1(Struct, tag_field='type_', tag='a'):
-    type_: ClassVar[Annotated[Union[Literal['a'], UnsetType], Meta(title='Type ')]] = (
-        'a'
-    )
+    pass
 
 
 class Type2(Struct, tag_field='type_', tag='b'):
-    type_: ClassVar[Annotated[Union[Literal['b'], UnsetType], Meta(title='Type ')]] = (
-        'b'
-    )
+    pass
 
 
 class UnrelatedType(Struct):

tests/data/expected/main/jsonschema/discriminator_literals_msgspec_keyword_only.py

@@ -4,21 +4,17 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, Union
 
 from msgspec import Meta, Struct, UnsetType
 
 
 class Type1(Struct, kw_only=True, tag_field='type_', tag='a'):
-    type_: ClassVar[Annotated[Union[Literal['a'], UnsetType], Meta(title='Type ')]] = (
-        'a'
-    )
+    pass
 
 
 class Type2(Struct, kw_only=True, tag_field='type_', tag='b'):
-    type_: ClassVar[Annotated[Union[Literal['b'], UnsetType], Meta(title='Type ')]] = (
-        'b'
-    )
+    pass
 
 
 class UnrelatedType(Struct, kw_only=True):

tests/data/expected/main/jsonschema/discriminator_literals_msgspec_keyword_only_omit_defaults.py

@@ -4,21 +4,17 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, Union
 
 from msgspec import Meta, Struct, UnsetType
 
 
 class Type1(Struct, omit_defaults=True, kw_only=True, tag_field='type_', tag='a'):
-    type_: ClassVar[Annotated[Union[Literal['a'], UnsetType], Meta(title='Type ')]] = (
-        'a'
-    )
+    pass
 
 
 class Type2(Struct, omit_defaults=True, kw_only=True, tag_field='type_', tag='b'):
-    type_: ClassVar[Annotated[Union[Literal['b'], UnsetType], Meta(title='Type ')]] = (
-        'b'
-    )
+    pass
 
 
 class UnrelatedType(Struct, omit_defaults=True, kw_only=True):

tests/data/expected/main/jsonschema/discriminator_with_external_reference_msgspec.py

@@ -4,42 +4,31 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, Union
 
 from msgspec import UNSET, Meta, Struct, UnsetType
 
 
 class Type1(Struct, tag_field='type_', tag='a'):
-    type_: ClassVar[Annotated[Union[Literal['a'], UnsetType], Meta(title='Type ')]] = (
-        'a'
-    )
+    pass
 
 
 class Type2(Struct, tag_field='type_', tag='b'):
-    type_: ClassVar[Annotated[Union[Literal['b'], UnsetType], Meta(title='Type ')]] = (
-        'b'
-    )
     ref_type: Union[
         Annotated[Type1, Meta(description='A referenced type.')], UnsetType
     ] = UNSET
 
 
 class Type4(Struct, tag_field='type_', tag='d'):
-    type_: ClassVar[Annotated[Union[Literal['d'], UnsetType], Meta(title='Type ')]] = (
-        'd'
-    )
+    pass
 
 
 class Type5(Struct, tag_field='type_', tag='e'):
-    type_: ClassVar[Annotated[Union[Literal['e'], UnsetType], Meta(title='Type ')]] = (
-        'e'
-    )
+    pass
 
 
 class Type3(Struct, tag_field='type_', tag='c'):
-    type_: ClassVar[Annotated[Union[Literal['c'], UnsetType], Meta(title='Type ')]] = (
-        'c'
-    )
+    pass
 
 
 class Response(Struct):

tests/data/expected/main/jsonschema/discriminator_with_external_references_folder_msgspec/inner_folder/artificial_folder/type_1.py

@@ -4,12 +4,8 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
-
-from msgspec import Meta, Struct, UnsetType
+from msgspec import Struct
 
 
 class Type1(Struct, tag_field='type_', tag='a'):
-    type_: ClassVar[Annotated[Union[Literal['a'], UnsetType], Meta(title='Type ')]] = (
-        'a'
-    )
+    pass

tests/data/expected/main/jsonschema/discriminator_with_external_references_folder_msgspec/inner_folder/schema.py

@@ -4,9 +4,9 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, Union
 
-from msgspec import Meta, Struct, UnsetType
+from msgspec import Meta, Struct
 
 from .. import type_4
 from ..subfolder import type_5
@@ -15,9 +15,7 @@
 
 
 class Type3(Struct, tag_field='type_', tag='c'):
-    type_: ClassVar[Annotated[Union[Literal['c'], UnsetType], Meta(title='Type ')]] = (
-        'c'
-    )
+    pass
 
 
 class Response(Struct):

tests/data/expected/main/jsonschema/discriminator_with_external_references_folder_msgspec/inner_folder/type_2.py

@@ -4,17 +4,14 @@
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, Union
 
 from msgspec import UNSET, Meta, Struct, UnsetType
 
 from .artificial_folder import type_1
 
 
 class Type2(Struct, tag_field='type_', tag='b'):
-    type_: ClassVar[Annotated[Union[Literal['b'], UnsetType], Meta(title='Type ')]] = (
-        'b'
-    )
     ref_type: Union[
         Annotated[type_1.Type1, Meta(description='A referenced type.')], UnsetType
     ] = UNSET