WIP Add support for const (#243)

* Add support for const

* fix ruff

---------

Co-authored-by: Jakob Zanker <jakob@project-lary.com>
Co-authored-by: luolingchun <luolingchun@outlook.com>

Author: 3 people

flask_openapi3/models/schema.py

@@ -54,5 +54,6 @@ class Schema(BaseModel):
     externalDocs: ExternalDocumentation | None = None
     example: Any | None = None
     deprecated: bool | None = None
+    const: str | None = None
 
     model_config = {"populate_by_name": True}

tests/test_openapi.py

@@ -488,3 +488,25 @@ def test_schema_bigint(request):
     max_nr = 9223372036854775807
     obj = Schema(maximum=max_nr)
     assert obj.model_dump()["maximum"] == max_nr
+
+
+def test_convert_literal_with_single_value_to_const(request):
+    test_app = OpenAPI(request.node.name)
+    test_app.config["TESTING"] = True
+
+    class MyResponse(BaseModel):
+        foobar: Literal["baz"]
+
+    @test_app.post("/test", responses={200: MyResponse})
+    def endpoint_test():
+        print("do nothing")
+
+    with test_app.test_client() as client:
+        resp = client.get("/openapi/openapi.json")
+        assert resp.status_code == 200
+        print("###", resp.json)
+        assert resp.json["components"]["schemas"]["MyResponse"]["properties"]["foobar"] == {
+            "const": "baz",
+            "title": "Foobar",
+            "type": "string",
+        }