[Question] optional fields in openapi body from dataclass vs validate

[morph027]

Description

Not sure if it's related to sanic-ext at all or just missing understanding of dataclasses on my side ;)

I'm trying to describe and validate a json body w/ optional parameters.

from dataclasses import dataclass
from typing import List, Optional
from sanic import Sanic
from sanic.response import json
from sanic_ext import openapi, validate


app = Sanic("Test")


@dataclass
class Test:
    foo: str
    bar: int
    foobar: Optional[List[str]]


@app.post("/")
@openapi.body({"application/json": Test})
@validate(Test)                                                                                                                                               
async def test(request, body: Test):
    return json({"message": "Hello world!"})

This renders as request body describing foobar as object or nullable.

Validation now fails when foobar is omitted (correct so far)

$ curl -d '{"foo": "string", "bar": 1337}' http://127.0.0.1:8000/
{"description":"Bad Request","status":400,"message":"Invalid request body: Test. Error: missing a required argument: 'foobar'"}

Now, if i set a default for foobar like

@dataclass
class Test:
    foo: str
    bar: int
    foobar: Optional[List[str]] = None

the request works as expected:

$ curl -d '{"foo": "string", "bar": 1337}' http://127.0.0.1:8000/
{"message":"Hello world!"}

But now API docs renders as object without nullable:

Question

How can i combine the two? Show foobar as nullable in docs and pass validation w/ parameter omitted?

Do i need 2 seperate dataclasses?

Also, is it possible to show foobar as list of strings in the docs instead of object (derives from Optional, i guess).

Versions

• sanic 21.12.0
• sanic-ext 21.12.3

[ahopkins]

I think it ultimately is a bug in need of fixing to properly read more information from the dataclass if it is available.

[morph027]

🥳 It works, thank you!

I do have another corner case where a request does have only one optional parameter.

Example:

from dataclasses import dataclass, field
from typing import Optional
from sanic import Sanic
from sanic.log import logger
from sanic.response import json
from sanic_ext import openapi, validate


app = Sanic("Test")


@dataclass
class Test:
    bar: Optional[str] = field(default_factory=str)


@app.post("/")
@openapi.body({"application/json": Test})
@validate(Test)
async def test(request, body: Test):
    return json({"message": "Hello world!"})

If i omit the body completely, the validation fails again due to the request does not have a body (None):

$ curl -X POST http://127.0.0.1:8000/
{"description":"Bad Request","status":400,"message":"Invalid request body: Test. Error: Value 'None' is not a dict"}

Stacktrace:

[2022-01-21 13:33:53 +0100] [30740] [ERROR] Exception occurred while handling uri: 'http://127.0.0.1:8000/'
Traceback (most recent call last):
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extras/validation/validators.py", line 24, in validate_body
    return validator(model, body)
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extras/validation/validators.py", line 36, in _validate_annotations
    return check_data(model, body, schema, allow_multiple, allow_coerce)
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extras/validation/check.py", line 83, in check_data
    raise TypeError(f"Value '{data}' is not a dict")
TypeError: Value 'None' is not a dict

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "handle_request", line 83, in handle_request
    )
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extensions/openapi/openapi.py", line 213, in handler
    retval = await retval
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extras/validation/decorator.py", line 37, in decorated_function
    await do_validation(
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extras/validation/setup.py", line 41, in do_validation
    validation = validate_body(validator, model, data)
  File "/home/morph/python3/lib/python3.10/site-packages/sanic_ext/extras/validation/validators.py", line 26, in validate_body
    raise ValidationError(
sanic_ext.exceptions.ValidationError: Invalid request body: Test. Error: Value 'None' is not a dict

Passing an empty body works:

$ curl -X POST -d '{}' http://127.0.0.1:8000/
{"message":"Hello world!"}

Any way to specify a fallback for a None body?

[morph027]

Ah, nevermind, read through the docs again and found a convenient way to create a dummy body using a middleware.

from dataclasses import dataclass, field
from typing import Optional

from sanic import Sanic
from sanic.response import json
from sanic_ext import openapi, validate

app = Sanic("Test")


@dataclass
class Test:
    bar: Optional[str] = field(default_factory=str)


@app.middleware("request")
async def dummy_body_if_empty(request):
    if not request.body:
        request.body = b'{}'


@app.post("/")
@openapi.body({"application/json": Test})
@validate(Test)
async def test(request, body: Test):
    return json({"message": "Hello world!"})