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Fix non-idempotent indentation of consecutive block comments #7103

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Fix non-idempotent indentation of consecutive block comments #7103

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4 changes: 3 additions & 1 deletion src/missed_spans.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -245,7 +245,9 @@ impl<'a> FmtVisitor<'a> {
.rev()
.find(|rev_c| ![' ', '\t'].contains(rev_c));

let fix_indent = last_char.map_or(true, |rev_c| ['{', '\n'].contains(&rev_c));
let starts_output_line = !self.buffer.is_empty() && self.buffer.ends_with('\n');

@matthewhughes934 matthewhughes934 Sep 9, 2026 •
edited by rustbot
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I'm not sure I understand this fix from a glance, can you explain what is the importance of self.buffer ending in a newline?

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@saberoueslati saberoueslati Sep 9, 2026

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self.buffer ending in \n means the next comment starts a new output line. For /*A*/ /*B*/, writing /*A*/ adds a newline via the _ => arm at the end of process_comment. But last_char still sees the closing / of /*A*/ in the original source, so fix_indent is false and /*B*/ gets one space instead of the block indent. starts_output_line catches this and applies self.block_indent on the first pass, so reformatting no longer changes the output.

I hope this clears it up

let fix_indent =
starts_output_line || last_char.map_or(true, |rev_c| ['{', '\n'].contains(&rev_c));
let mut on_same_line = false;

let comment_indent = if fix_indent {
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36 changes: 36 additions & 0 deletions tests/source/issue-7019.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
fn two() -> usize {
/*A*/ /*B*/
1 + 2
}

fn three() -> usize {
/*A*/ /*B*/ /*C*/
1 + 2
}

fn nested() -> usize {
{
{
/*A*/ /*B*/ /*C*/
1 + 2
}
}
}

fn between_statements() -> usize {
let a = 1;
/*A*/ /*B*/
let b = 2;
a + b
}

fn trailing_inline() -> usize {
let a = 1; /*trailing*/
a
}

fn already_canonical() -> usize {
/*A*/
/*B*/
1 + 2
}
42 changes: 42 additions & 0 deletions tests/target/issue-7019.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
fn two() -> usize {
/*A*/
/*B*/
1 + 2
}

fn three() -> usize {
/*A*/
/*B*/
/*C*/
1 + 2
}

fn nested() -> usize {
{
{
/*A*/
/*B*/
/*C*/
1 + 2
}
}
}

fn between_statements() -> usize {
let a = 1;
/*A*/
/*B*/
let b = 2;
a + b
}

fn trailing_inline() -> usize {
let a = 1; /*trailing*/
a
}

fn already_canonical() -> usize {
/*A*/
/*B*/
1 + 2
}