Strange behavior of "Optional[T]" and "Suppress"

[KrobotP]

Once more I am here with my example app:

class MySpec(BaseModel):
    some_set: Set[int] = Field(
        default={1, 2, 3},
        decsription="Some set of integers",
        title="Some set",
    )

    some_string: str = Field(
        decsription="Some string without a default value.",
        title="SomeSTR",
    )


def add_spec(spec: MySpec):
    print(spec.here_comes_the_trouble)

if __name__ == "__main__":
    tyro.cli(add_spec)

Everything works fine here:

$ python3.11 example.py --help
usage: example.py [-h] [--spec.some-set [INT [INT ...]]] --spec.some-string STR

╭─ options ───────────────────────────────────────────────╮
│ -h, --help              show this help message and exit │
╰─────────────────────────────────────────────────────────╯
╭─ spec options ──────────────────────────────────────────╮
│ --spec.some-set [INT [INT ...]]                         │
│                         (default: '{1, 2, 3}')          │
│ --spec.some-string STR  (required)                      │
╰─────────────────────────────────────────────────────────╯

Now I would like to make some-string parameter optional:

class MySpec(BaseModel):
    some_set: Set[int] = Field(
        default={1, 2, 3},
        decsription="Some set of integers",
        title="Some set",
    )

    some_string: Optional[str] = Field(
        decsription="Some string without a default value.",
        title="SomeSTR",
    )

Everything still works, but with a warning:

$ python3.11 example.py --help
/usr/local/lib/python3.11/site-packages/tyro/_fields.py:181: UserWarning: The field some_string is annotated with type <class 'str'>, but the default value None has type <class 'NoneType'>. We'll try to handle this gracefully, but it may cause unexpected behavior.
  warnings.warn(
usage: example.py [-h] [--spec.some-set [INT [INT ...]]] [--spec.some-string {None}|STR]

╭─ options ─────────────────────────────────────────╮
│ -h, --help        show this help message and exit │
╰───────────────────────────────────────────────────╯
╭─ spec options ────────────────────────────────────╮
│ --spec.some-set [INT [INT ...]]                   │
│                   (default: '{1, 2, 3}')          │
│ --spec.some-string {None}|STR                     │
│                   (default: None)                 │
╰───────────────────────────────────────────────────╯

I am not quite sure why there is a warning as some-string is declared as union of "None" and "str", having "None" as default value should be legal.

Moreover, when I try to suppress an optional option, no suppression is made at all:

class MySpec(BaseModel):
    some_set: Set[int] = Field(
        default={1, 2, 3},
        decsription="Some set of integers",
        title="Some set",
    )

    some_string: tyro.conf.Suppress[Optional[str]] = Field(
        decsription="Some string without a default value.",
        title="SomeSTR",
    )

$ python3.11 example.py --help
/usr/local/lib/python3.11/site-packages/tyro/_fields.py:181: UserWarning: The field some_string is annotated with type <class 'str'>, but the default value None has type <class 'NoneType'>. We'll try to handle this gracefully, but it may cause unexpected behavior.
  warnings.warn(
usage: example.py [-h] [--spec.some-set [INT [INT ...]]] [--spec.some-string {None}|STR]

╭─ options ─────────────────────────────────────────╮
│ -h, --help        show this help message and exit │
╰───────────────────────────────────────────────────╯
╭─ spec options ────────────────────────────────────╮
│ --spec.some-set [INT [INT ...]]                   │
│                   (default: '{1, 2, 3}')          │
│ --spec.some-string {None}|STR                     │
│                   (default: None)                 │
╰───────────────────────────────────────────────────╯

Suppression is ignored even when I remove warning by setting default value of type str.

Suppresion works, when Optional is not used, or when I prefix option name with _.

[brentyi]

Hi @KrobotP, can you confirm which version of pydantic you're using?

This:

from typing import Optional, Set

from pydantic import BaseModel, Field

import tyro


class MySpec(BaseModel):
    some_set: Set[int] = Field(
        default={1, 2, 3},
        decsription="Some set of integers",
        title="Some set",
    )

    some_string: tyro.conf.Suppress[Optional[str]] = Field(
        decsription="Some string without a default value.",
        title="SomeSTR",
    )


tyro.cli(MySpec)

appears to give me the right behavior with pydantic==2.9.2; an error that some_string is missing a default value. When I set the default value, the error disappears and the argument is correctly suppressed.

As a note, it seems like you've also misspelled description in all of your examples.

[KrobotP]

Hello @brentyi, I am currently using older version (1.2) as we are in the middle of transfer to the newer 2+. Thus, we wuld like to work with both versions for some time.