Get the StringConstraints directly from the Identifier type

[baderdean]

Problem:
FastAPI does not validate custom string build using Annotated[str, StringConstraints(...)]

Temporary solution
My solution is to annotate the constrained type with Path again, then it seems to work:

from typing import Annotated

from fastapi import FastAPI, Path
from pydantic import StringConstraints

# In my case this is imported from a lib with pydantic but without fastapi,
# so it can't be changed to Annotated[str, Path(pattern=r"^[a-fA-F0-9]+$")]
Identifier = Annotated[str, StringConstraints(pattern=r"^[a-fA-F0-9]+$")]


app = FastAPI()


@app.get("/{some_id}")
async def get_something(some_id: Annotated[Identifier, Path()]):
    return some_id

Feature request
Would be nice if fastapi would be able to get the constraint directly from the Identifier type without being required to add Annotated[Identifier, Path()].

Originally posted by @JasperJuergensen in #10105 (comment)

[Kludex]

What the OP wants is this:

from typing import Annotated

from fastapi import FastAPI, Path
from pydantic import StringConstraints

Identifier = Annotated[str, StringConstraints(pattern=r"^[a-fA-F0-9]+$")]

app = FastAPI()

@app.get("/{some_id}")
async def get_something(some_id: Identifier):
    return some_id

A similar feature request is to use pydantic.Field.

[Dragon-GCS]

It is because missing the matadata when none of Annotated args is FieldInfo or Depends
I've commit a fix pr #10356 . Hope it's work

[ramnes]

Isn't it pretty much the same as #10259 and #10109?