Fastapi: [QUESTION] fastapi issue of swagger display ?

[euri10]

Description

I have a pydantic model with Enum and Union parameters, and while they both appear in Schema, in a post route they are not displayed in the Example edit section.
I hesitated to file a bug but I;d prefer to ask if that's something that's feasible first.

I was surprised and made a small exercice, take this model:

class DisplayMe(BaseModel):
    my_bool: bool
    my_float: float
    my_str: str
    my_int: int
    my_dict: dict
    # my_list: list
    # my_tuple: tuple
    # my_set: set
    # my_List_str: List[str]
    # my_tuple_str_int: Tuple[str, int]
    # my_dict_str_int: Dict[str, int]
    # my_union_str_int: Union[str, int]
    # my_enum: Enum
    my_emailstr: EmailStr
    my_name_email: NameEmail
    my_urlstr: UrlStr
    my_dsn: DSN
    my_bytes: bytes
    my_decimal: Decimal
    my_uuid1: UUID1
    my_uuid3: UUID3
    my_uuid4: UUID4
    my_uuid5: UUID5
    my_uuid: UUID
    my_filepath: FilePath
    my_directorypath: DirectoryPath
    my_path: Path
    my_datetime: datetime
    my_date: date

add this route:

@router.post("/testypes")
async def types(tt: DisplayMe):
    return tt

should you uncomment any of the pydantic types commented in the DisplayMe model above, then the Edit section is empty, there's nothing to edit.

But I can see them in schema, for instance on the below screen my_tuple is visible in the Schema:

Now if I put them commented they are in the Edit section:

question is : is it possible to have the commented pydantic types in the swagger edit section, I'm mostyl interested in Union and Enum in fact :)

[tiangolo]

Sorry for the delay.

In fact, some of those types are generating errors.

I'll check this more thoroughly as it seems there's a bug in Pydantic to solve (which I probably introduced there while implementing all the JSON Schema stuff).

If you are curious, I create the API with your code, then I check the raw JSON OpenAPI endpoint, then I copy it and paste it here: https://editor.swagger.io, there I can debug it and see all the errors. You can check that if you want to see what is the actual problem in the generated schemas.

[euri10]

I've pushed on my fork a branch that tries to help on this (https://github.com/euri10/fastapi/tree/display_pydantic_types)

I used 2 models, Working and Failing:

• Working contains all types that are in pydantic documentation, types which fail are commented out
• Failing contains all failing types commented above

the test_openapi doesn't test anything, it's more to print the json schema to paste like you said on https://editor.swagger.io

I guess most errors come from upstream in pydantic schema generation, just hope this branch helps in figuring out what types may cause issues, pydantic schema is a rather impressive topic to jump in :boom: :scream_cat: , not sure I would not where to look at ! :octopus:

[tiangolo]

Yeah, Pydantic internals are quite heavy. It even uses undocumented Python features.

I'll check it there with your examples to see where I did something wrong.

[haizaar]

I hit this as well, both for Unions and Enum.

Here is the simple reproduction for Enum:

from enum import Enum

from fastapi import FastAPI
from pydantic import BaseModel


class ModelName(Enum):
    alexnet = "alexnet"
    resnet = "resnet"
    lenet = "lenet"


class Model(BaseModel):
    size: int
    name: ModelName


app = FastAPI()


@app.post("/")
def post(model: Model):
    pass

And the docs miss the name field indeed:

Workaround for Enum - inherit it from str as well:

class ModelName(str, Enum):
    alexnet = "alexnet"
    resnet = "resnet"
    lenet = "lenet"

(This is how pydantic docs do it BTW). That immediately made me think that there is a problem with schema, but it's not - Model.schema_json() return the following:

{
  "title": "Model",
  "type": "object",
  "properties": {
    "size": {
      "title": "Size",
      "type": "integer"
    },
    "name": {
      "title": "Name",
      "enum": [
        "alexnet",
        "resnet",
        "lenet"
      ]
    }
  },
  "required": [
    "size",
    "name"
  ]
}

[tiangolo]

I just realized I replied in the PR but not here.

Let me copy some sections from there:

The way to use an enum would be like:

class MyEnum(Enum):
    a = "foo"
    b = "bar"

and then:

my_enum: MyEnum

---

@haizaar about enums with str, good point. That's an issue in Swagger UI itself: https://github.com/swagger-api/swagger-ui/issues/3761

But is good to know there's a workaround for the API docs. Maybe we could use it in the FastAPI docs examples.

---

On the other side, about Union, they show up in Swagger UI in the schema, but not in the example, that's also Swagger UI: https://github.com/swagger-api/swagger-ui/issues/3803

[fgimian]

I just encountered this one today too with a Union 😄

Are there any workarounds for getting a Union[str, List[str]] to display in the docs?

Thanks so much
Fotis

[fgimian]

After a little more digging, I can see that FastAPI is doing the right thing here (the OpenAPI JSOn generated is correct). The problem seems to be on swagger-ui's end. Some related issues are https://github.com/swagger-api/swagger-ui/issues/4819 and https://github.com/swagger-api/swagger-ui/issues/3803

I guess we'll need to wait for this to be fixed upstream 😄

Cheers
Fotis