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Delay trailing whitespace output buffer #2244

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Merged
j178 merged 1 commit into from
Jun 23, 2026
+24 −9
Merged

Delay trailing whitespace output buffer #2244

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33 changes: 24 additions & 9 deletions crates/prek/src/hooks/pre_commit_hooks/fix_trailing_whitespace.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -112,8 +112,8 @@ async fn fix_file(
let file_path = file_base.join(filename);
let content = fs_err::tokio::read(&file_path).await?;

let mut output = Vec::with_capacity(content.len());
let mut modified = false;
let mut output = None;
let mut copied_len = 0;
for line in content.split_inclusive(|&b| b == b'\n') {
let line_ending = detect_line_ending(line);
let mut trimmed = &line[..line.len() - line_ending.len()];
Expand All @@ -129,17 +129,32 @@ async fn fix_file(
trimmed = trimmed.trim_end_with(|c| chars.contains(&c));
}

output.extend_from_slice(trimmed);
if markdown_end {
output.extend_from_slice(MARKDOWN_LINE_BREAK);
modified |= trimmed.len() + MARKDOWN_LINE_BREAK.len() + line_ending.len() != line.len();
let modified_len = if markdown_end {
trimmed.len() + MARKDOWN_LINE_BREAK.len() + line_ending.len()
} else {
modified |= trimmed.len() + line_ending.len() != line.len();
trimmed.len() + line_ending.len()
};
let modified = modified_len != line.len();

if modified {
let output = output.get_or_insert_with(|| {
let mut output = Vec::with_capacity(content.len());
output.extend_from_slice(&content[..copied_len]);
output
});
output.extend_from_slice(trimmed);
if markdown_end {
output.extend_from_slice(MARKDOWN_LINE_BREAK);
}
output.extend_from_slice(line_ending);
} else if let Some(output) = output.as_mut() {
output.extend_from_slice(line);
}
output.extend_from_slice(line_ending);

copied_len += line.len();
}

if modified {
if let Some(output) = output {
fs_err::tokio::write(&file_path, &output).await?;
Ok((1, format!("Fixing {}\n", filename.display()).into_bytes()))
} else {
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