Stabilize RootModel config rendering

Author: koxudaxi

src/datamodel_code_generator/model/pydantic_v2/root_model.py

@@ -9,6 +9,7 @@
 
 from datamodel_code_generator import Error
 from datamodel_code_generator.imports import IMPORT_ANY, Import
+from datamodel_code_generator.model.base import _safe_extra_template_data
 from datamodel_code_generator.model.pydantic_v2.base_model import (
     _CONFIG_ITEMS_TEMPLATE_DATA_KEY,
     BaseModel,
@@ -95,8 +96,27 @@ def add_sequence_interface(self, item_type: str, slice_type: str) -> None:
 
     def render(self, *, class_name: str | None = None) -> str:
         """Render the RootModel and validate custom sequence templates when needed."""
+        use_custom_template = self.template_file_path.is_absolute()
+        fields = self.fields if use_custom_template else self.rendered_fields
+        if fields:
+            _ = fields[0].type_hint
         self._sync_config_items()
-        rendered = super().render(class_name=class_name)
+        extra_template_data = (
+            self.extra_template_data if use_custom_template else _safe_extra_template_data(self.extra_template_data)
+        )
+        rendered = self._render(
+            class_name=class_name or self.class_name,
+            fields=fields,
+            decorators=self.decorators,
+            base_class=self.base_class,
+            methods=self.methods,
+            description=self.description
+            if use_custom_template or not self.FORMAT_DESCRIPTION_AS_DOCSTRING
+            else self.rendered_description,
+            dataclass_arguments=self.dataclass_arguments,
+            path=self.path,
+            **extra_template_data,
+        )
         self._validate_custom_template_sequence_interface(rendered)
         return rendered