Thanks for opening your first issue here! We'll come back to you as soon as we can.
In the meantime, check out the #python channel on our Powertools for AWS Lambda Discord: Invite link

Hi @dschro-1993 can you show me your api handler code that uses Foo?

Handler:

from aws_lambda_powertools import event_handler

# ...router-imports...

api = event_handler.APIGatewayRestResolver(
  enable_validation = True
)

api.include_router(...)

def entrypoint(request: dict, context: dict) -> dict:
  return api.resolve(
    request,
    context,
  )

Router:

from aws_lambda_powertools.event_handler.api_gateway import Router

from models import Foo

router = Router()

@router.post("/foo")
def create(foo: Foo) -> dict:
  """Foo Create-Request"""
  # ...

Model:

class Foo(BaseModel):
  AccountId: str = Field(pattern=r"^\d{12}$")

Can you please tell me which Pydantic version are you using?

I've just deployed this code for a test:

from aws_lambda_powertools import Logger
from aws_lambda_powertools.event_handler import (
    APIGatewayRestResolver,
)
from aws_lambda_powertools.event_handler.api_gateway import Router
from pydantic import Field, BaseModel

logger = Logger()


class Foo(BaseModel):
    AccountId: str = Field(pattern=r"^\d{12}$")


router = Router()


@router.post(
    "/foo",
)
def helloworld(foo: Foo) -> dict:
    logger.info("Hello, World!", foo=foo)
    return {"accountId": foo.AccountId}


app = APIGatewayRestResolver(enable_validation=True)
app.include_router(router)


@logger.inject_lambda_context
def lambda_handler(event, context):
    return app.resolve(event, context)

A request with a wrong body failed:

But a request with a good body succeeded:

I use the Powertools lambda layer arm64 in its latest version:
https://docs.powertools.aws.dev/lambda/python/latest/#lambda-layer

# ...
resource "aws_lambda_function" "foo" {
  #...
  layers = [
    "arn:aws:lambda:${data.aws_region.current.name}:017000801446:layer:AWSLambdaPowertoolsPythonV2-Arm64:68"
  ]
}

Oh damn, that layer is built upon Pydantic v1, correct? So I would have to bundle v2 on my own if I want to see v2 behaviour in my lambda?

Let me try locally with v1 first to understand if this is the cause of problem

Got it, with Pydantic v1 you have to use regex instead of pattern! Just tested it and it works :D

We have an issue collecting interest for a managed Layer that includes Pydantic v2. Can you add your +1 there?

If this solves your problem, let me know if we can close this issue :)

Thanks for your investigation, that was very helpful!
Left a +1 for the v2 layer :)

Awesome! Thank you for opening this report :) Closing it for now

⚠️COMMENT VISIBILITY WARNING⚠️

This issue is now closed. Please be mindful that future comments are hard for our team to see.

If you need more assistance, please either tag a team member or open a new issue that references this one.

If you wish to keep having a conversation with other community members under this issue feel free to do so.