Feature: add spaces_within_parenthesized_items option.

[henriquemelicias]

Hello!

Tracking issue: #5435

This feature adds the option to put a space after '(' and before ')' on items surrounded by parentheses (on function/method declarations, calls, ...).

Tips on improvements would be highly appreciated!

[ytmimi]

Thanks for submitting your first PR 🎉

Could you open a feature request issue where we can discuss the motivation for this change as well as the scope of the new option. This PR seems focused on functions and methods, but I think there are some other areas where parentheses appear that we might also need to consider. For example, Tuple literals (a, b, c), Tuple Structs Foo()? patterns in if let if let Some(x), etc.

I also want to point out that rustfmt is an implementation of the Rust Style Guide, and there are cases like single line calls and tuple literals where this options directly goes against the prescribed behavior. rustfmt does support options that allow users to go against the style guide, but we always need to keep the style guide in mind when making these types of changes.

There's also a pending PR (#5386), which wraps certain cast expressions in parens to avoid compiler errors. I wonder if we need to hold off on this PR until after that one is merged to avoid any issues with how this option might behave with those changes.

Tips on improvements would be highly appreciated!

Default configuration tests typically live in tests/source/configs and tests/target/configs. If this is going to be a binary option we'll want to have tests for both the true and false cases.

It would also be nice to include comments in weird places to see if that affects anything.

For example, the current tests show that fn foo1() {} is left unchanged, but what happens if we add a comment and write fn foo1(/*comment*/) {}?. Do we now add spaces between the parens and the comment?

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All that said, lets start with the feature request issue and take it from there.

[BrokenShards]

I would personally like this feature very much, partially because I write a lot of C++ and C# so I am used to having this as a formatting option in Visual Studio, but mainly because I've found that spacing brackets out can make it a lot easier to keep my place when dealing with nested parenthesis, especially with code that has a lot of nested function calls.
Any progress on the status of this PR?

[ytmimi]

@henriquemelicias thanks for reaching out again. This is still a fairly low-priority feature request for the team, and I don't think we'll have the bandwidth to look into this in the near future.