[BUG] No `Optional` typing in args that accept `None` in `Console`.

[paw-lu]

Some arguments to rich.console.Console—like width—accept None as an argument and are documented as Optional but are typed as only int, raising some type checking errors if width=None is passed.

https://github.com/willmcgugan/rich/blob/a05a5a1c2f95f25db70ac3657e99f0bab652e2cd/rich/console.py#L577

[willmcgugan]

What type checker are you using? Mypy will assume Optional when you set the default value to None.

[paw-lu]

"""script.py"""
def foo(x : int = None) -> None:
    ...


foo(x=None)

In this case it fails default Pyre.

❯ pyre
ƛ Using virtual environment site-packages in search path...
ƛ Found 2 type errors!
src/script.py:1:8 Incompatible variable type [9]: x is declared to have type `int` but is used as type `None`.
src/script.py:5:4 Incompatible parameter type [6]: Expected `int` for 1st parameter `x` to call `foo` but got `None`.

It will fail default pytype as well

❯ python -m pytype src/script.py
Computing dependencies
Analyzing 1 sources with 0 local dependencies
ninja: Entering directory `.pytype'
[1/1] check script
FAILED: /Users/pawlu/Documents/scratch/typing-optional/.pytype/pyi/script.pyi
/Users/pawlu/Documents/scratch/typing-optional/.venv/bin/python -m pytype.single --imports_info /Users/pawlu/Documents/scratch/typing-optional/.pytype/imports/script.imports --module-name script -V 3.8 -o /Users/pawlu/Documents/scratch/typing-optional/.pytype/pyi/script.pyi --analyze-annotated --nofail --quick /Users/pawlu/Documents/scratch/typing-optional/src/script.py
File "/Users/pawlu/Documents/scratch/typing-optional/src/script.py", line 5, in <module>: Function foo was called with the wrong arguments [wrong-arg-types]
         Expected: (x: int = ...)
  Actually passed: (x: None)

For more details, see https://google.github.io/pytype/errors.html#wrong-arg-types
ninja: build stopped: subcommand failed.
Leaving directory '.pytype'

You're right that it does pass mypy by default, but it will fail if you use --strict due to it invoking --no-implicit-optional.

❯ python -m mypy --strict src/script.py
mypy.ini: No [mypy] section in config file
src/script.py:1: error: Incompatible default for argument "x" (default has type "None", argument has type "int")
src/script.py:5: error: Argument "x" to "foo" has incompatible type "None"; expected "int"
Found 2 errors in 1 file (checked 1 source file)

For what it's worth, I think mypy plans to (maybe) eventually switch --no-implicit-optional to the default, since PEP 484 was adjusted.

[paw-lu]

If you're interested, #1182 attempts to impliment the Optional typing throughout Rich.

[willmcgugan]

It's somewhat irritating to have a convenient feature added only to have it taken away. However since it looks like you've done the work, I have no issue with changing it.

[paw-lu]

It's somewhat irritating to have a convenient feature added only to have it taken away.

To be clear the feature is probably staying in mypy (am not a dev, just reading the issues) by explicitly calling --implicit-optional flag, it's just that the default might change, and that the adjustment to PEP 484 no longer recommends assumed optional types. So you could probably pass your own tests using that flag, and future users would turn off implicit optional warnings explicity for rich.

Regardless, thanks for reviewing the PR and thanks for the project!