Docs: condecimal gives type error "Illegal type annotation: call expression not allowed" #354

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• I added a very descriptive title to this issue.
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Example Code

from pydantic import condecimal
from sqlmodel import Field, SQLModel


class Lineitem(SQLModel, table=True):
    price: condecimal(max_digits=5, decimal_places=2) = Field(default=0)

Description

The above code yields a Pylance error in VsCode:

Illegal type annotation: call expression not allowed Pylance(reportGeneralTypeIssues)

And with mypy:

$ mypy code/example.py
code/example.py:6: error: Invalid type comment or annotation
code/example.py:6: note: Suggestion: use condecimal[...] instead of condecimal(...)
Found 1 error in 1 file (checked 1 source file)

This is definitely a Pydantic issue: pydantic/pydantic#156.

However, I thought it might be a good idea to add to the docs for decimals that this error can occur. There's a comment on the pydantic issue that gives an ugly workaround, which in my case would look something like:

from decimal import Decimal
from typing import TYPE_CHECKING
from typing_extensions import reveal_type
from pydantic import condecimal
from sqlmodel import Field, SQLModel


class Lineitem(SQLModel, table=True):
    if TYPE_CHECKING:
        price: Decimal = Field(default=0)
    else:
        price: condecimal(max_digits=5, decimal_places=2) = Field(default=0)


item = Lineitem(price=Decimal(1))
if TYPE_CHECKING:
    reveal_type(item.price) # result: Type of "item.price" is "Decimal"

item = Lineitem(price=Decimal(9.999)) # should throw a validation error

The mypy result is:

$ mypy code/example_fixed.py
code/example_fixed.py:17: note: Revealed type is "_decimal.Decimal"
Success: no issues found in 1 source file

I don't think this workaround should be added to the docs: nobody would go this far to make a type checker happy. I was thinking the docs could say something like:

Warning (or Tip?)
Type checkers will complain about the type of condecimal being the result of a callable, or be confused by it. There is no fix for this, so to silence the error add # type: ignore:

class Lineitem(SQLModel, table=True):
    price: condecimal(max_digits=5, decimal_places=2) = Field(default=0)  # type: ignore

Operating System

macOS

Operating System Details

$ sw_vers
ProductName: macOS
ProductVersion: 12.4
BuildVersion: 21F79

SQLModel Version

0.0.6

Python Version

Python 3.10.2

Additional Context

Screenshot of Pylance error: