Merge fc8a4e11fc into e6d09027e5

fastapi/openapi/models.py

@@ -10,7 +10,7 @@ from fastapi._compat import (
     with_info_plain_validator_function,
 )
 from fastapi.logger import logger
-from pydantic import AnyUrl, BaseModel, Field
+from pydantic import AnyUrl, BaseModel, Field, validator
 from typing_extensions import Annotated, Literal, TypedDict
 from typing_extensions import deprecated as typing_deprecated
 
@@ -439,6 +439,15 @@ class OpenAPI(BaseModelWithConfig):
     tags: Optional[List[Tag]] = None
     externalDocs: Optional[ExternalDocumentation] = None
 
+    @validator("tags")
+    def check_tags(cls, tags):  # type: ignore
+        unique_names = set()
+        assert not any(
+            t.name in unique_names or unique_names.add(t.name)
+            for t in tags  # type: ignore
+        ), "Tag names must be unique"
+        return tags
+
 
 _model_rebuild(Schema)
 _model_rebuild(Operation)

fastapi/openapi/utils.py

@@ -565,5 +565,10 @@ def get_openapi(
     if webhook_paths:
         output["webhooks"] = webhook_paths
     if tags:
-        output["tags"] = tags
+        # discard tags with non-unique names as it is against the OpenAPI spec
+        # https://swagger.io/specification/#openapi-object
+        names = set()
+        output["tags"] = [
+            t for t in tags if t["name"] not in names and not names.add(t["name"])
+        ]  # type: ignore
     return jsonable_encoder(OpenAPI(**output), by_alias=True, exclude_none=True)  # type: ignore

tests/test_duplicate_openapi_tags.py

@@ -0,0 +1,22 @@
+"""Test case for possible tag duplication at OpenAPI object level"""
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+app = FastAPI(
+    openapi_tags=[
+        {"name": "items", "description": "items1"},
+        {"name": "items", "description": "items2"},
+    ]
+)
+
+client = TestClient(app)
+
+
+def test_openapi_for_duplicates():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    tag_list = response.json()["tags"]
+    assert len(tag_list) == 1
+    assert tag_list[0]["name"] == "items"
+    assert tag_list[0]["description"] == "items1"