feat: improve model docstring header with title fallback + add test

Author: Doug Borg

src/openapi_python_generator/language_converters/python/templates/models.jinja2

@@ -10,11 +10,13 @@ from pydantic import BaseModel, Field
 
 class {{ schema_name }}(BaseModel):
     """
-    {{ schema.title }} model
-    {% if schema.description != None %}
+    {% if schema.title %}{{ schema.title }}{% else %}{{ schema_name }}{% endif %} model
+    {% if schema.description %}
     {{ schema.description }}
     {% endif %}
-
+    {% if parent_comment %}
+    {{ parent_comment }}
+    {% endif %}
     """
     {% for property in properties %}
 

src/openapi_python_generator/language_converters/python/templates/models_pydantic_2.jinja2

@@ -10,11 +10,13 @@ from pydantic import BaseModel, Field
 
 class {{ schema_name }}(BaseModel):
     """
-    {{ schema.title }} model
-    {% if schema.description != None %}
+    {% if schema.title %}{{ schema.title }}{% else %}{{ schema_name }}{% endif %} model
+    {% if schema.description %}
     {{ schema.description }}
     {% endif %}
-
+    {% if parent_comment %}
+    {{ parent_comment }}
+    {% endif %}
     """
     model_config = {
         "populate_by_name": True,

tests/test_model_docstring.py

@@ -0,0 +1,28 @@
+from openapi_pydantic.v3 import Schema, Components, DataType
+
+from openapi_python_generator.language_converters.python.model_generator import generate_models
+from openapi_python_generator.common import PydanticVersion
+
+
+def test_model_docstring_title_used_when_present_and_fallback_to_name():
+    """Ensure we prefer schema.title when present, fallback to schema name, and never emit 'None model'."""
+    widget_schema = Schema(  # type: ignore[arg-type]
+        type=DataType.OBJECT,
+        title="Fancy Widget",
+        properties={"id": Schema(type=DataType.INTEGER)},  # type: ignore[arg-type]
+    )
+    no_title_schema = Schema(  # type: ignore[arg-type]
+        type=DataType.OBJECT,
+        properties={"name": Schema(type=DataType.STRING)},  # type: ignore[arg-type]
+    )
+
+    components = Components(schemas={"Widget": widget_schema, "NoTitle": no_title_schema})  # type: ignore[arg-type]
+    models = {m.file_name: m for m in generate_models(components, PydanticVersion.V2)}
+
+    widget_content = models["Widget"].content
+    notitle_content = models["NoTitle"].content
+
+    assert "Fancy Widget model" in widget_content  # title used
+    assert "NoTitle model" in notitle_content  # fallback used
+    assert "None model" not in widget_content
+    assert "None model" not in notitle_content