Rustfmt sometimes breaks lists in doc-comments

[WaffleLapkin]

Rustfmt breaks sub-list with + (diff from cargo +nightly fmt -- --check --config "wrap_comments=true")

 //! List:
-//! - Sub list:
-//!   + very long #1 blah blah blah blah blah blah blah blah blah blah blah blah
-//!   + very long #2 blah blah blah blah blah blah blah blah blah blah blah blah
+//! - Sub list: + very long #1 blah blah blah blah blah blah blah blah blah blah
+//!   blah blah + very long #2 blah blah blah blah blah blah blah blah blah blah
+//!   blah blah
 //! - ...

Changing + in sublist to - fixes that.

[ytmimi]

Confirming I can reproduce this with rustfmt 1.5.1-nightly (a451a39d 2022-07-25). using the following input:

//! List:
//! - Sub list:
//!   + very long #1 blah blah blah blah blah blah blah blah blah blah blah blah
//!   + very long #2 blah blah blah blah blah blah blah blah blah blah blah blah

For anyone wanting to work on this this issue is that we don't consider + the start of an itemized line.

The relevant code can be found here:

rustfmt/src/comment.rs

Lines 433 to 453 in a451a39

	/// Block that is formatted as an item.
	///
	/// An item starts with either a star `*` a dash `-` or a greater-than `>`.
	/// Different level of indentation are handled by shrinking the shape accordingly.
	struct ItemizedBlock {
	/// the lines that are identified as part of an itemized block
	lines: Vec<String>,
	/// the number of characters (typically whitespaces) up to the item sigil
	indent: usize,
	/// the string that marks the start of an item
	opener: String,
	/// sequence of characters (typically whitespaces) to prefix new lines that are part of the item
	line_start: String,
	}
	impl ItemizedBlock {
	/// Returns `true` if the line is formatted as an item
	fn is_itemized_line(line: &str) -> bool {
	let trimmed = line.trim_start();
	trimmed.starts_with("* ") || trimmed.starts_with("- ") || trimmed.starts_with("> ")
	}

[ytmimi]

linking tracking issue for wrap_comments #3347

[thaqibm]

Maybe I can help this!

[ytmimi]

@thaqib0437, that's great news! feel free to reach out if you have any questions

[thaqibm]

Is there a guide on building, testing my changes with custom inputs, and adding teat cases?

[ytmimi]

@thaqib0437 check out the Create Test Cases section of the contributing guide. Running cargo build is all you need to do in order to build rustfmt locally?

[thaqibm]

Trying to add a test case but its not running with warp_comments=true
test file:

//  rustfmt-wrap_comments=true
//! List:
//! - Sub list:
//!   + very long #1 blah blah blah blah blah blah blah blah blah blah blah blah
//!   + very long #2 blah blah blah blah blah blah blah blah blah blah blah blah

[thaqibm]

Created a PR
#5560