Remove multiple trailing lines in comments

Previously, rustfmt would remove one blank, trailing line in a comment every time it ran, so formatting was not idempotent if a comment had multiple trailing lines. Comments are only reformatted in this way if `comment::rewrite_comment_inner` is called, which is enabled by any of the config options `normalize_comments`, `wrap_comments`, or `format_code_in_doc_comments` (for doc comments only). Absent those config options, no trailing line reformatting occurs at all. In this commit, when the existing condition that detects a blank, trailing line is true, any preceding blank lines are removed from the reformatted comment. A source/target "system test" was added to prevent regression. Signed-off-by: Ross Williams <[email protected]>
rust-lang · overhacked · May 11, 2024 · Jul 31, 2024 · Jul 31, 2024 · c7504a2269b831438672a436d97777e540060faf
commit c7504a2269b831438672a436d97777e540060faf
diff --git a/src/comment.rs b/src/comment.rs
@@ -811,7 811,13 @@ impl<'a> CommentRewrite<'a> {
  } else if self.is_prev_line_multi_line && !line.is_empty() {
  self.result.push(' ')
  } else if is_last && line.is_empty() {
- // trailing blank lines are unwanted
  // Trailing blank lines are unwanted; if the last line is blank, look for additional,
  // preceding blank lines to remove, also.
  let trailing_line = self.comment_line_separator.trim_end_matches(' ');
  while self.result.ends_with(trailing_line) {
  self.result
  .truncate(self.result.len() - trailing_line.len());
  }
  if !self.closer.is_empty() {
  self.result.push_str(&self.indent_str);
  }

diff --git a/tests/source/comment_trailing_lines.rs b/tests/source/comment_trailing_lines.rs
@@ -0,0 1,21 @@
 // rustfmt-wrap_comments: true
 
 //! Module comment with multiple trailing lines
 //!
 //!
 
 /// Doc comment with multiple trailing lines
 ///
 ///
 pub mod foo {}
 
 /// Doc comment with one trailing line
 ///
 pub mod bar {}
 
 /*
  * Block comment with multiple trailing lines
  *
  *
  */
 pub mod block {}
diff --git a/tests/target/comment_trailing_lines.rs b/tests/target/comment_trailing_lines.rs
@@ -0,0 1,14 @@
 // rustfmt-wrap_comments: true
 
 //! Module comment with multiple trailing lines
 
 /// Doc comment with multiple trailing lines
 pub mod foo {}
 
 /// Doc comment with one trailing line
 pub mod bar {}
 
 /*
  * Block comment with multiple trailing lines
  */
 pub mod block {}