PyYAML: Permit width: float for pure-Python dump(...)

[kmurphy4]

To prevent PyYAML from wrapping any lines, it's possible to pass width=float("inf"), but the current type hints don't like that. This works at runtime:

>>> s = yaml.dump({"foo": "bar" * 1000}, width=float("inf"))
>>> print(s)
foo: barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar...

but mypy says

floatwidth.py:2: error: No overload variant of "dump" matches argument types "Dict[str, str]", "float"
floatwidth.py:2: note: Possible overload variants:
floatwidth.py:2: note:     def dump(data: Any, stream: _WriteStream[Any], Dumper: Any = ..., *, default_style: Optional[str] = ..., default_flow_style: Optional[bool] = ..., canonical: Optional[bool] = ..., indent: Optional[int] = ..., width: Optional[int] = ..., allow_unicode: Optional[bool] = ..., line_break: Optional[str] = ..., encoding: Optional[str] = ..., explicit_start: Optional[bool] = ..., explicit_end: Optional[bool] = ..., version: Optional[Tuple[int, int]] = ..., tags: Optional[Mapping[str, str]] = ..., sort_keys: bool = ...) -> None
floatwidth.py:2: note:     def dump(data: Any, stream: None = ..., Dumper: Any = ..., *, default_style: Optional[str] = ..., default_flow_style: Optional[bool] = ..., canonical: Optional[bool] = ..., indent: Optional[int] = ..., width: Optional[int] = ..., allow_unicode: Optional[bool] = ..., line_break: Optional[str] = ..., encoding: Optional[str] = ..., explicit_start: Optional[bool] = ..., explicit_end: Optional[bool] = ..., version: Optional[Tuple[int, int]] = ..., tags: Optional[Mapping[str, str]] = ..., sort_keys: bool = ...) -> Any
Found 1 error in 1 file (checked 1 source file)

Poking through the PyYAML source, it looks the width parameter could probably be anything "comparable", as it's only compared via the < operator.

For the LibYAML implementation, however, we have to use ints:

>>> stream = io.StringIO()
>>> dumper = yaml.CDumper(stream, width=float("inf"))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/yaml/cyaml.py", line 81, in __init__
    version=version, tags=tags)
  File "ext/_yaml.pyx", line 973, in _yaml.CEmitter.__init__ (ext/_yaml.c:14797)
OverflowError: cannot convert float infinity to integer

I'm not familiar with Cython, though I assume this is because of the definition of yaml_emitter_set_width.

[Avasam]

Ref python/typing#1160

[srittau]

I'm sorry for the late response. The change looks good functionally, but i would prefer if we would define a type alias _Inf = float or similar (with an explanatory comment) and then use int | _Inf | None. While functionally identically, it makes the intent clearer and would make it easier to potentially change it to Literal['inf'] (or whatever) in the future.

[kmurphy4]

No worries, thanks for the review :)

I'm happy to add the type alias, but flake8 complains about int | float (see the last commit message).

[AlexWaygood]

flake8-pyi is pretty dumb about these things — it'll detect int | float and yell at you, but if you do _Inf: TypeAlias = float, it'll be absolutely cool with you using int | _Inf :)

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

The requested changes were made

[AlexWaygood]

Thanks!