Convert (most of the) configuration values from pyproject.toml to strings

[ichard26]

Resolves #1458.

---

We need to convert all configuration values from the pyproject.toml
file because Click already does value processing and conversion and
it only expects the exact Python type or string. Click doesn't like
the integer 1 as a boolean for example. This also means other
unsupported types like datetime.time will be rejected by Click as
an invalid value instead of throwing an exception.

We only skip converting objects that are an instance of
collections.abc.Iterable because it's almost impossible to get back
the original iterable of a stringified iterable.

---

After this change, these following values will be accepted for each of the configuration options in pyproject.toml:

Option	Accepted values
Boolean type / flag type --pyi -S / --skip-string-normalization --check --diff --color / --no-color --fast / --safe --quiet --verbose	Integers 0 1 Strings (case insensitive) "f" "false" "n" "no" "0" "t" "true" "y" "yes" "1" Boolean true True (technically a string) false False (technically a string)
Integer type -l / --line-length	Any integer Any stringified integer
Choice type -t / --target-version	The choices available for that option.
Text type -c / --code --include --exclude --force-exclude	Any text still accepted.

And --version, --help, and --config are still allowed in pyproject.toml 😆

[ichard26]

I went with collections.abc.Iterable since I don't really know what iterable types the TOML parser might return. If it is overkill, I could just replace it with list since from my limited testing, that is the only iterable the TOML parser returns (well other than strings).

[cooperlees]

I think toml and is like JSON and only has lists and dicts right? So list would probably be safe, but so would be Iterable. So I don’t have any strong opinion.

[ichard26]

Well, I have no experience with JSON, but your argument makes sense. The TOML parser shouldn't change what it returns that much since it does follow the TOML specification, which shouldn't change that often. I've changed it to (list, dict) just to be safe.

[ichard26]

Completely unrelated, but the primer check is still a bit flaky on Windows, this run preferred to fail apparently.
https://github.com/ichard26/black/runs/728070221?check_suite_focus=true

Isn't much of a problem though, it seems to be always an issue with the event loop so it's easy to spot.

EDIT: oh, excuse me?

PermissionError: [WinError 32] The process cannot access the file because it is being used by another process

[cooperlees]

EDIT: oh, excuse me?

PermissionError: [WinError 32] The process cannot access the file because it is being used by another process

I guess we should open a dedicated issue for this. We can always stop Windows as 99% of value is finding logic area in black, it shouldn't be Windows specific, but, still, always nice to check on all platforms.