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oriziorizi
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fix(formatter): avoid usize underflow on over-wide comment prefixes
 format_leading_comment computed max_comment_width as `max_line_width - cur_indent - n_slashes - n_exclamations - n_leading_spaces` in usize. When the prefix exceeds max_line_width (a deeply-indented or long divider comment), this underflows: debug panics, release wraps. Use saturating_sub so the width floors at 0 and the comment is left unwrapped. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
1 parent 0ef1296 commit 81c4dd6

4 files changed

Lines changed: 20 additions & 4 deletions

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‎crates/cairo-lang-formatter/src/formatter_impl.rs‎

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@@ -794,11 +794,13 @@ fn format_leading_comment(content: &str, cur_indent: usize, max_line_width: usiz
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let mut last_line_broken = false;
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for line in content.lines() {
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let orig_comment_line = CommentLine::from_string(line.to_string());
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// Saturate: the prefix (indent + slashes + exclamations + leading spaces) can exceed
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// `max_line_width` for a deeply-indented or many-slash comment, which would underflow.
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let max_comment_width = max_line_width
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- cur_indent
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- orig_comment_line.n_slashes
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- orig_comment_line.n_exclamations
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- orig_comment_line.n_leading_spaces;
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.saturating_sub(cur_indent)
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.saturating_sub(orig_comment_line.n_slashes)
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.saturating_sub(orig_comment_line.n_exclamations)
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.saturating_sub(orig_comment_line.n_leading_spaces);
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// The current line is initialized with the previous line only if it was broken (to avoid
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// merging user separated lines).
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let mut current_line = if last_line_broken

‎crates/cairo-lang-formatter/src/test.rs‎

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@@ -98,6 +98,15 @@ use crate::{FormatterConfig, get_formatted_file};
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false,
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false
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)]
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#[test_case(
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"test_data/cairo_files/comment_overflow.cairo",
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"test_data/expected_results/comment_overflow.cairo",
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false,
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false,
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false,
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false,
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false
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)]
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#[test_case(
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"test_data/cairo_files/use_merge.cairo",
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"test_data/expected_results/use_merge.cairo",

‎crates/cairo-lang-formatter/test_data/cairo_files/comment_overflow.cairo‎

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@@ -0,0 +1,2 @@
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//////////////////////////////////////////////////////////////////////////////////////////////////////////// section divider
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fn f() {}

‎crates/cairo-lang-formatter/test_data/expected_results/comment_overflow.cairo‎

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//////////////////////////////////////////////////////////////////////////////////////////////////////////// section
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//////////////////////////////////////////////////////////////////////////////////////////////////////////// divider
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fn f() {}

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