Fastapi: [QUESTION] Is it possible to generate openapi.json with "nullable" : "true" for non-required property?

Created on 8 Jan 2020 · 5Comments · Source: tiangolo/fastapi

Description

Is it possible to generate openapi.json with "nullable" : "true" for non-required property?

Additional context

I'm using NSwag to generate C# code from FastAPI openapi.json. I need to set "nullable" as "true" to make it work correctly.

I have a FastAPI Model like this:

class Topic(BaseModel):
    first_id: str = None

I want to get a schema like this:

"Topic": {
  "title": "Topic",
  "type": "object",
    "properties": {
      "first_id": {
        "title": "First_Id",
        "type": "string",
        "nullable" : "true"
      }
  }
}

But I haven't found a way to set the field "nullable". And if it's not provided, it is "false" by default.

question

Source

dennismeissel

Most helpful comment

You can use Field to set nullable=True by default.

Example:


from fastapi import FastAPI, Depends, Query, HTTPException
from typing import Optional
from pydantic import BaseModel, Field

app = FastAPI()


class Model(BaseModel):
    a: Optional[int]
    b: Optional[int] = None
    c: Optional[int] = Field(None, nullable=True)


@app.get("/test", response_model=Model)
def foo(m: Model):
    return m

Component in /openapi.json

...
Model: {
    title: "Model",
    required: [
        "c"
    ],
    type: "object",
    properties: {
    a: {
        title: "A",
        type: "integer"
    },
    b: {
        title: "B",
        type: "integer"
    },
    c: {
        title: "C",
        type: "integer",
        nullable: true
    }
}
...

Slyfoxy on 21 Jan 2020

👍2

All 5 comments

You can use Field to set nullable=True by default.

Example:


from fastapi import FastAPI, Depends, Query, HTTPException
from typing import Optional
from pydantic import BaseModel, Field

app = FastAPI()


class Model(BaseModel):
    a: Optional[int]
    b: Optional[int] = None
    c: Optional[int] = Field(None, nullable=True)


@app.get("/test", response_model=Model)
def foo(m: Model):
    return m

Component in /openapi.json

...
Model: {
    title: "Model",
    required: [
        "c"
    ],
    type: "object",
    properties: {
    a: {
        title: "A",
        type: "integer"
    },
    b: {
        title: "B",
        type: "integer"
    },
    c: {
        title: "C",
        type: "integer",
        nullable: true
    }
}
...

Slyfoxy on 21 Jan 2020

👍2

@Slyfoxy Thanks for answer, it helped!

I found out, that Field is not working with FastAPI

But Schema did the job!

from pydantic import BaseModel, Schema

class Topic(BaseModel):
    first_id: str = Schema(None, nullable=True)

And /openapi.json

"Topic": {
    "title": "Topic",
    "type": "object",
    "properties": {
        "first_id": {
        "title": "First_Id",
        "type": "string",
        "nullable": true
        }
    }
}

dennismeissel on 23 Jan 2020

😄1

Fastapi works with 'Field' from 'pydantic' in latest version of 'fastapi' with 'pydantic=1.0'. Just update it :)

Slyfoxy on 23 Jan 2020

Ah, ok, understood!

Thank you :)

dennismeissel on 23 Jan 2020

Thanks for the help here @Slyfoxy ! :cake: :bowing_man:

Thanks @dennismeissel for reporting back and closing the issue :+1: