Fix array RootModel default value handling in parser (#2963)

* Fix array RootModel default value handling in parser

* docs: update llms.txt files

Generated by GitHub Actions

* Show uncovered lines when coverage check fails

* Fix coverage report path in CI workflow

* Remove redundant comments and use direct attribute access

* Remove unnecessary comment

* Inline _should_field_be_required to improve branch coverage

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: koxudaxi

.github/workflows/test.yaml

@@ -120,23 +120,34 @@ jobs:
           pattern: .coverage.*
           merge-multiple: true
       - name: Combine and report coverage
+        id: coverage
         run: tox run -e coverage --skip-uv-sync --skip-pkg-install
+        continue-on-error: true
         env:
           UV_PYTHON_PREFERENCE: only-managed
+      - name: Show uncovered lines on failure
+        if: steps.coverage.outcome == 'failure'
+        run: |
+          echo "::error::Coverage check failed. Lines not covered:"
+          COVERAGE_FILE=.tox/.coverage .tox/coverage/bin/coverage report --show-missing --fail-under=0 | grep -v "100%"
       - name: Upload HTML report
+        if: always()
         uses: actions/upload-artifact@v4
         with:
           name: html-report
           path: .tox/htmlcov
       - name: Upload coverage to Codecov
-        if: success() || failure()
+        if: always()
         uses: codecov/codecov-action@v5
         with:
           flags: unittests
           files: .tox/coverage.xml
           fail_ci_if_error: true
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+      - name: Fail if coverage check failed
+        if: steps.coverage.outcome == 'failure'
+        run: exit 1
 
   check:
     name: ${{ matrix.tox_env }}

docs/cli-reference/field-customization.md

@@ -3912,7 +3912,7 @@ This is useful when schemas have descriptive titles that should be preserved.
     class ProcessingStatusUnionTitle(BaseModel):
         __root__: (
             ProcessingStatusDetail | ExtendedProcessingTask | ProcessingStatusTitle
-        ) = Field(..., title='Processing Status Union Title')
+        ) = Field('COMPLETED', title='Processing Status Union Title')
 
 
     class ProcessingTaskTitle(BaseModel):

docs/llms-full.txt

@@ -11680,7 +11680,7 @@ This is useful when schemas have descriptive titles that should be preserved.
     class ProcessingStatusUnionTitle(BaseModel):
         __root__: (
             ProcessingStatusDetail | ExtendedProcessingTask | ProcessingStatusTitle
-        ) = Field(..., title='Processing Status Union Title')
+        ) = Field('COMPLETED', title='Processing Status Union Title')
 
 
     class ProcessingTaskTitle(BaseModel):

src/datamodel_code_generator/model/pydantic/base_model.py

@@ -220,7 +220,7 @@ def __str__(self) -> str:  # noqa: PLR0912
             elif isinstance(discriminator, dict):  # pragma: no cover
                 data["discriminator"] = discriminator["propertyName"]
 
-        if self.required and not self.has_default:
+        if self.required:
             default_factory = None
         elif self.default is not UNDEFINED and self.default is not None and "default_factory" not in data:
             default_factory = self._get_default_as_pydantic_model()
@@ -249,7 +249,7 @@ def __str__(self) -> str:  # noqa: PLR0912
 
         if self.use_annotated:
             field_arguments = self._process_annotated_field_arguments(field_arguments)
-        elif self.required and not default_factory:
+        elif self.required:
             field_arguments = ["...", *field_arguments]
         elif not default_factory:
             default_repr = repr_set_sorted(self.default) if isinstance(self.default, set) else repr(self.default)

src/datamodel_code_generator/model/template/pydantic/BaseModel_root.jinja2

@@ -24,7 +24,7 @@ class {{ class_name }}({{ base_class }}):{% if comment is defined %}  # {{ comme
     {%- else %}
     __root__: {{ field.type_hint }}
     {%- endif %}
-    {%- if not field.has_default_factory_in_field and not ((field.required and not field.has_default) or (field.represented_default == 'None' and field.strip_default_none))
+    {%- if not field.has_default_factory_in_field and not (field.required or (field.represented_default == 'None' and field.strip_default_none))
             %} = {{ field.represented_default }}
     {%- endif -%}
     {%- endif %}

src/datamodel_code_generator/model/template/pydantic_v2/RootModel.jinja2

@@ -42,7 +42,7 @@ class {{ class_name }}({{ base_class }}{%- if fields -%}[{{get_type_hint(fields,
     {%- else %}
     root: {{ field.type_hint }}
     {%- endif %}
-    {%- if not field.has_default_factory_in_field and not ((field.required and not field.has_default) or (field.represented_default == 'None' and field.strip_default_none))
+    {%- if not field.has_default_factory_in_field and not (field.required or (field.represented_default == 'None' and field.strip_default_none))
             %} = {{ field.represented_default }}
     {%- endif -%}
     {%- endif %}

src/datamodel_code_generator/parser/jsonschema.py

@@ -903,7 +903,7 @@ def _create_synthetic_enum_obj(
             title=original.title,
             description=original.description,
             x_enum_varnames=final_varnames,
-            default=original.default if original.has_default else None,
+            **({"default": original.default} if original.has_default else {}),
         )
 
     def is_constraints_field(self, obj: JsonSchemaObject) -> bool:
@@ -1528,22 +1528,6 @@ def _apply_title_as_name(self, name: str, obj: JsonSchemaObject) -> str:
             return sanitize_module_name(obj.title, treat_dot_as_module=self.treat_dot_as_module)
         return name
 
-    def _should_field_be_required(
-        self,
-        *,
-        in_required_list: bool = True,
-        has_default: bool = False,
-        is_nullable: bool = False,
-    ) -> bool:
-        """Determine if a field should be marked as required."""
-        if self.force_optional_for_required_fields:
-            return False
-        if self.apply_default_values_for_required_fields and has_default:  # pragma: no cover
-            return False
-        if is_nullable:
-            return False
-        return in_required_list
-
     def _deep_merge(self, dict1: dict[Any, Any], dict2: dict[Any, Any]) -> dict[Any, Any]:
         """Deep merge two dictionaries, combining nested dicts and lists."""
         result = dict1.copy()
@@ -3054,7 +3038,7 @@ def parse_list_item(
             for index, item in enumerate(target_items)
         ]
 
-    def parse_array_fields(  # noqa: PLR0912
+    def parse_array_fields(  # noqa: PLR0912, PLR0915
         self,
         name: str,
         obj: JsonSchemaObject,
@@ -3069,12 +3053,17 @@ def parse_array_fields(  # noqa: PLR0912
             required: bool = False
             nullable: Optional[bool] = None  # noqa: UP045
         else:
-            required = not (obj.has_default and self.apply_default_values_for_required_fields)
+            required = not obj.has_default
             if self.strict_nullable:
                 nullable = obj.nullable if obj.has_default or required else True
             else:
                 required = not obj.nullable and required
-                nullable = None
+                if obj.nullable:
+                    nullable = True
+                elif obj.has_default:
+                    nullable = False
+                else:
+                    nullable = None
         is_tuple = False
         suppress_item_constraints = False
         if isinstance(obj.items, JsonSchemaObject):
@@ -3259,10 +3248,27 @@ def parse_root_type(  # noqa: PLR0912, PLR0914, PLR0915
             data_type = self.data_type_manager.get_data_type(
                 Types.any,
             )
-        required = self._should_field_be_required(
-            has_default=obj.has_default,
-            is_nullable=bool(obj.nullable),
-        )
+        is_type_alias = self.data_model_root_type.IS_ALIAS
+        if self.force_optional_for_required_fields:
+            required = False
+            nullable = None
+            has_default_override = True
+            default_value = obj.default if obj.has_default else None
+        elif obj.nullable:
+            required = False
+            nullable = True
+            has_default_override = True
+            default_value = obj.default if obj.has_default else None
+        elif obj.has_default and not is_type_alias:
+            required = False
+            nullable = False
+            has_default_override = True
+            default_value = obj.default
+        else:
+            required = True
+            nullable = None
+            has_default_override = obj.has_default
+            default_value = obj.default if obj.has_default else UNDEFINED
         name = self._apply_title_as_name(name, obj)
         if not reference:
             reference = self.model_resolver.add(path, name, loaded=True, class_name=True)
@@ -3276,20 +3282,18 @@ def parse_root_type(  # noqa: PLR0912, PLR0914, PLR0915
             fields=[
                 self.data_model_field_type(
                     data_type=data_type,
-                    default=obj.default,
+                    default=default_value,
                     required=required,
                     constraints=constraints,
-                    nullable=obj.nullable
-                    if self.strict_nullable and obj.nullable is not None
-                    else (False if self.strict_nullable and obj.has_default else None),
+                    nullable=nullable,
                     strip_default_none=self.strip_default_none,
                     extras=self.get_field_extras(obj),
                     use_annotated=self.use_annotated,
                     use_field_description=self.use_field_description,
                     use_field_description_example=self.use_field_description_example,
                     use_inline_field_description=self.use_inline_field_description,
                     original_name=None,
-                    has_default=obj.has_default,
+                    has_default=has_default_override,
                 )
             ],
             custom_base_class=self._resolve_base_class(name, obj.custom_base_path),
@@ -3298,7 +3302,7 @@ def parse_root_type(  # noqa: PLR0912, PLR0914, PLR0915
             path=self.current_source_path,
             nullable=obj.type_has_null,
             treat_dot_as_module=self.treat_dot_as_module,
-            default=obj.default if obj.has_default else UNDEFINED,
+            default=default_value if has_default_override else UNDEFINED,
         )
         self.results.append(data_model_root_type)
         return self.data_type(reference=reference)
@@ -3326,10 +3330,7 @@ def _parse_multiple_types_with_properties(
         )
 
         is_nullable = obj.nullable or obj.type_has_null
-        required = self._should_field_be_required(
-            has_default=obj.has_default,
-            is_nullable=bool(is_nullable),
-        )
+        required = not (self.force_optional_for_required_fields or is_nullable)
 
         reference = self.model_resolver.add(path, name, loaded=True, class_name=True)
         self._set_schema_metadata(reference.path, obj)

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

@@ -47,7 +47,7 @@ class ExtendedProcessingTasksTitle(BaseModel):
 class ProcessingStatusUnionTitle(BaseModel):
     __root__: (
         ProcessingStatusDetail | ExtendedProcessingTask | ProcessingStatusTitle
-    ) = Field(..., title='Processing Status Union Title')
+    ) = Field('COMPLETED', title='Processing Status Union Title')
 
 
 class ProcessingTaskTitle(BaseModel):