Add support for booleans and floats in OpenAPI Schema const

[flxdot]

We encountered the problem that the Pydantic Schemas for the OpenAPI spec, do not support the const keyword if it is of type boolean.

Why do I think it should be supported?

The OpenAPI Specification explicitly marks the const keyword as unsupported. Nevertheless it should not result in exceptions if the keyword is present.

I furthermore did not find any evidence in JSON Schema that would limit the types valid for the const keyword to be string or integer only.

Thus I suggest allowing boolean as well as floats as constant values.

Example

The following is minimal example in FastAPI that would produce such a schema:

fromtypingimportLiteralimportuvicornfromfastapiimportFastAPIfrompydanticimportBaseModel, FieldclassResponseWithConstantBool(BaseModel):
message: str=Field(...)
is_welcome: Literal[True] =Field(True)
app=FastAPI()
@app.get("/", response_model=ResponseWithConstantBool)asyncdefroot():
return {"message": "Hello World"}
if__name__=="__main__":
uvicorn.run(app)

Generated OpenAPI Specification

{
"openapi": "3.1.0",
"info": {
"title": "FastAPI",
"version": "0.1.0"
},
"paths": {
"/": {
"get": {
"summary": "Root",
"operationId": "root__get",
"responses": {
"200": {
"description": "Successful Response",
"content": {
"application/json": {
"schema": {
"$ref": "#/components/schemas/ResponseWithConstantBool"
}
}
}
}
}
}
}
},
"components": {
"schemas": {
"ResponseWithConstantBool": {
"properties": {
"message": {
"type": "string",
"title": "Message"
},
"is_welcome": {
"type": "boolean",
"enum": [true],
"const": true,
"title": "Is Welcome",
"default": true
}
},
"type": "object",
"required": [
"message"
],
"title": "ResponseWithConstantBool"
}
}
}
}

[dbanty]

I believe OpenAPI 3.1 is what added support for const, but you're right, there's no reason it shouldn't support all the primitives. Thanks for the PR!