editor: Fix splitting brackets inside line comments

[lingyaochu]

Objective

Closes #59229

When adding a newline, Zed has a bit of intelligence to do more work than just inserting a \n. For comment lines, it simply extends the comment:

Before
// This is a comment, ˇThis is another comment


After
// This is a comment, 
// ˇThis is another comment

And when the cursor is inside bracket pairs, Zed inserts another newline to move the closing bracket to a new line:

Before
fn main() {ˇ}


After
fn main() {
    ˇ
}

However, when we have a comment line with the cursor inside a bracket pair, both mechanisms apply, resulting in an unintended state where the closing bracket is kicked out of the comment:

Before
// {ˇ}

After
// {
// ˇ
}

We definitely do not need the bracket extension rule when we are adding a newline inside comments. We want comment lines inside brackets to be split like this:

// {
// ˇ}

Solution

• Disable Bracket Extra Newline in Comments: When a line comment delimiter is detected, we override the default newline_config to set extra_line_additional_indent to None .
• Avoid Rule Conflicts (Short-circuiting): The three newline customization helpers (line comment, block comment, and list item) are mutually exclusive. I refactored their execution from a sequential list into an if let Some ... else if let Some branch. This prevents subsequent rules from having side effects on newline_config when a match has already occurred.

Testing

A new test named test_newline_comments_with_brackets is introduced in crates/editor/src/editor_tests.rs, All tests in the editor crate were verified using cargo test -p editor .

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content adheres to Zed's UI standards (UX/UI and icon guidelines)
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

---

Release Notes:

• Fixed an issue where splitting brackets inside line comments inserted an extra line and broke the comment formatting

[ChristopherBiscardi]

thanks!