PostgresDsn does not accept correct postgresql:///dbname since 2.10, was accepted before

[wereii]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

Before 2.10, PostgresDsn would accept postgresql:///dbname which is a valid DSN for postgres where the missing host means use local unix socket connection.
Now I get Input should be a valid URL, empty host

Example Code

import pydantic

class M(pydantic.BaseModel):
  dsn: pydantic.PostgresDsn


M(dsn="postgresql:///dbname")
print(M)

pydantic_core._pydantic_core.ValidationError: 1 validation error for M
dsn
  Input should be a valid URL, empty host [type=url_parsing, input_value='postgresql:///dbname', input_type=str]
    For further information visit https://errors.pydantic.dev/2.10/v/url_parsing

Python, Pydantic & OS Version

pydantic version: 2.10.2
        pydantic-core version: 2.27.1
          pydantic-core build: profile=release pgo=false
                 install path: /home/<user>/Projects/<snip>/<project_dir>/.venv/lib/python3.12/site-packages/pydantic
               python version: 3.12.7 (main, Oct  1 2024, 11:15:50) [GCC 14.2.1 20240910]
                     platform: Linux-6.12.1-arch1-1-x86_64-with-glibc2.40
             related packages: typing_extensions-4.12.2 mypy-1.13.0 pydantic-settings-2.6.1 fastapi-0.115.5
                       commit: unknown

[sydney-runkle]

Hmm, this is a consequence of pydantic/pydantic-core#1488.

We're now properly enforcing the host_required for PostgresDsn...

[sydney-runkle]

If you'd like to support a version without a required host, I'd recommend:

from pydantic import BaseModel, PostgresDsn, UrlConstraints
from typing import Annotated

class M(BaseModel):
  dsn: Annotated[PostgresDsn, UrlConstraints(host_required=False)]


m = M(dsn="postgresql:///dbname")
print(repr(m.dsn))
#> PostgresDsn('postgresql:///dbname')