Fix clippy::println_empty_string, clippy::while_let_on_iterator, clippy::while_let_on_iterator lint style violations (#36613)

Related: #36577

Release Notes:

- N/A

Cargo.toml

@@ -904,6 +904,7 @@ ok_expect = "warn"
 owned_cow = "warn"
 print_literal = "warn"
 print_with_newline = "warn"
+println_empty_string = "warn"
 ptr_eq = "warn"
 question_mark = "warn"
 redundant_closure = "warn"
@@ -924,7 +925,9 @@ unneeded_struct_pattern = "warn"
 unsafe_removed_from_name = "warn"
 unused_unit = "warn"
 unusual_byte_groupings = "warn"
+while_let_on_iterator = "warn"
 write_literal = "warn"
+write_with_newline = "warn"
 writeln_empty_string = "warn"
 wrong_self_convention = "warn"
 zero_ptr = "warn"

crates/agent/src/context.rs

@@ -362,7 +362,7 @@ impl Display for DirectoryContext {
         let mut is_first = true;
         for descendant in &self.descendants {
             if !is_first {
-                write!(f, "\n")?;
+                writeln!(f)?;
             } else {
                 is_first = false;
             }
@@ -650,7 +650,7 @@ impl TextThreadContextHandle {
 impl Display for TextThreadContext {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         // TODO: escape title?
-        write!(f, "<text_thread title=\"{}\">\n", self.title)?;
+        writeln!(f, "<text_thread title=\"{}\">", self.title)?;
         write!(f, "{}", self.text.trim())?;
         write!(f, "\n</text_thread>")
     }
@@ -716,7 +716,7 @@ impl RulesContextHandle {
 impl Display for RulesContext {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         if let Some(title) = &self.title {
-            write!(f, "Rules title: {}\n", title)?;
+            writeln!(f, "Rules title: {}", title)?;
         }
         let code_block = MarkdownCodeBlock {
             tag: "",

crates/agent2/src/thread.rs

@@ -163,7 +163,7 @@ impl UserMessage {
                     if !content.is_empty() {
                         let _ = write!(&mut markdown, "{}\n\n{}\n", uri.as_link(), content);
                     } else {
-                        let _ = write!(&mut markdown, "{}\n", uri.as_link());
+                        let _ = writeln!(&mut markdown, "{}", uri.as_link());
                     }
                 }
             }

crates/buffer_diff/src/buffer_diff.rs

@@ -2024,8 +2024,8 @@ mod tests {
         fn gen_working_copy(rng: &mut StdRng, head: &str) -> String {
             let mut old_lines = {
                 let mut old_lines = Vec::new();
-                let mut old_lines_iter = head.lines();
-                while let Some(line) = old_lines_iter.next() {
+                let old_lines_iter = head.lines();
+                for line in old_lines_iter {
                     assert!(!line.ends_with("\n"));
                     old_lines.push(line.to_owned());
                 }

crates/editor/src/display_map/block_map.rs

@@ -3183,9 +3183,9 @@ mod tests {
             // so we special case row 0 to assume a leading '\n'.
             //
             // Linehood is the birthright of strings.
-            let mut input_text_lines = input_text.split('\n').enumerate().peekable();
+            let input_text_lines = input_text.split('\n').enumerate().peekable();
             let mut block_row = 0;
-            while let Some((wrap_row, input_line)) = input_text_lines.next() {
+            for (wrap_row, input_line) in input_text_lines {
                 let wrap_row = wrap_row as u32;
                 let multibuffer_row = wraps_snapshot
                     .to_point(WrapPoint::new(wrap_row, 0), Bias::Left)

crates/editor/src/editor.rs

@@ -11021,7 +11021,7 @@ impl Editor {
                 let mut col = 0;
                 let mut changed = false;
 
-                while let Some(ch) = chars.next() {
+                for ch in chars.by_ref() {
                     match ch {
                         ' ' => {
                             reindented_line.push(' ');
@@ -11077,7 +11077,7 @@ impl Editor {
                 let mut first_non_indent_char = None;
                 let mut changed = false;
 
-                while let Some(ch) = chars.next() {
+                for ch in chars.by_ref() {
                     match ch {
                         ' ' => {
                             // Keep track of spaces. Append \t when we reach tab_size

crates/editor/src/indent_guides.rs

@@ -164,8 +164,8 @@ pub fn indent_guides_in_range(
     let end_anchor = snapshot.buffer_snapshot.anchor_after(end_offset);
 
     let mut fold_ranges = Vec::<Range<Point>>::new();
-    let mut folds = snapshot.folds_in_range(start_offset..end_offset).peekable();
-    while let Some(fold) = folds.next() {
+    let folds = snapshot.folds_in_range(start_offset..end_offset).peekable();
+    for fold in folds {
         let start = fold.range.start.to_point(&snapshot.buffer_snapshot);
         let end = fold.range.end.to_point(&snapshot.buffer_snapshot);
         if let Some(last_range) = fold_ranges.last_mut()

crates/editor/src/items.rs

@@ -103,9 +103,9 @@ impl FollowableItem for Editor {
                         multibuffer = MultiBuffer::new(project.read(cx).capability());
                         let mut sorted_excerpts = state.excerpts.clone();
                         sorted_excerpts.sort_by_key(|e| e.id);
-                        let mut sorted_excerpts = sorted_excerpts.into_iter().peekable();
+                        let sorted_excerpts = sorted_excerpts.into_iter().peekable();
 
-                        while let Some(excerpt) = sorted_excerpts.next() {
+                        for excerpt in sorted_excerpts {
                             let Ok(buffer_id) = BufferId::new(excerpt.buffer_id) else {
                                 continue;
                             };

crates/eval/src/eval.rs

@@ -706,7 +706,7 @@ fn print_report(
             println!("Average thread score: {average_thread_score}%");
         }
 
-        println!("");
+        println!();
 
         print_h2("CUMULATIVE TOOL METRICS");
         println!("{}", cumulative_tool_metrics);

crates/eval/src/instance.rs

@@ -913,9 +913,9 @@ impl RequestMarkdown {
             for tool in &request.tools {
                 write!(&mut tools, "# {}\n\n", tool.name).unwrap();
                 write!(&mut tools, "{}\n\n", tool.description).unwrap();
-                write!(
+                writeln!(
                     &mut tools,
-                    "{}\n",
+                    "{}",
                     MarkdownCodeBlock {
                         tag: "json",
                         text: &format!("{:#}", tool.input_schema)

crates/git/src/repository.rs

@@ -916,7 +916,7 @@ impl GitRepository for RealGitRepository {
                     .context("no stdin for git cat-file subprocess")?;
                 let mut stdin = BufWriter::new(stdin);
                 for rev in &revs {
-                    write!(&mut stdin, "{rev}\n")?;
+                    writeln!(&mut stdin, "{rev}")?;
                 }
                 stdin.flush()?;
                 drop(stdin);

crates/language/src/text_diff.rs

@@ -186,7 +186,7 @@ fn tokenize(text: &str, language_scope: Option<LanguageScope>) -> impl Iterator<
     let mut prev = None;
     let mut start_ix = 0;
     iter::from_fn(move || {
-        while let Some((ix, c)) = chars.next() {
+        for (ix, c) in chars.by_ref() {
             let mut token = None;
             let kind = classifier.kind(c);
             if let Some((prev_char, prev_kind)) = prev

crates/multi_buffer/src/multi_buffer_tests.rs

@@ -2250,11 +2250,11 @@ impl ReferenceMultibuffer {
             let base_buffer = diff.base_text();
 
             let mut offset = buffer_range.start;
-            let mut hunks = diff
+            let hunks = diff
                 .hunks_intersecting_range(excerpt.range.clone(), buffer, cx)
                 .peekable();
 
-            while let Some(hunk) = hunks.next() {
+            for hunk in hunks {
                 // Ignore hunks that are outside the excerpt range.
                 let mut hunk_range = hunk.buffer_range.to_offset(buffer);
 

crates/project/src/git_store/git_traversal.rs

@@ -42,8 +42,8 @@ impl<'a> GitTraversal<'a> {
         //   other_repo/
         //     .git/
         //   our_query.txt
-        let mut query = path.ancestors();
-        while let Some(query) = query.next() {
+        let query = path.ancestors();
+        for query in query {
             let (_, snapshot) = self
                 .repo_root_to_snapshot
                 .range(Path::new("")..=query)

crates/project/src/lsp_store.rs

@@ -13149,10 +13149,10 @@ fn ensure_uniform_list_compatible_label(label: &mut CodeLabel) {
     let mut offset_map = vec![0; label.text.len() + 1];
     let mut last_char_was_space = false;
     let mut new_idx = 0;
-    let mut chars = label.text.char_indices().fuse();
+    let chars = label.text.char_indices().fuse();
     let mut newlines_removed = false;
 
-    while let Some((idx, c)) = chars.next() {
+    for (idx, c) in chars {
         offset_map[idx] = new_idx;
 
         match c {

crates/settings/src/settings_json.rs

@@ -209,7 +209,7 @@ fn replace_value_in_json_text(
                     if ch == ',' {
                         removal_end = existing_value_range.end + offset + 1;
                         // Also consume whitespace after the comma
-                        while let Some((_, next_ch)) = chars.next() {
+                        for (_, next_ch) in chars.by_ref() {
                             if next_ch.is_whitespace() {
                                 removal_end += next_ch.len_utf8();
                             } else {

crates/tab_switcher/src/tab_switcher.rs

@@ -307,7 +307,7 @@ impl TabSwitcherDelegate {
                     (Reverse(history.get(&item.item.item_id())), item.item_index)
                 )
             }
-            eprintln!("");
+            eprintln!();
             all_items
                 .sort_by_key(|tab| (Reverse(history.get(&tab.item.item_id())), tab.item_index));
             all_items

crates/terminal_view/src/terminal_view.rs

@@ -1397,8 +1397,8 @@ fn possible_open_target(
             let found_entry = worktree
                 .update(cx, |worktree, _| {
                     let worktree_root = worktree.abs_path();
-                    let mut traversal = worktree.traverse_from_path(true, true, false, "".as_ref());
-                    while let Some(entry) = traversal.next() {
+                    let traversal = worktree.traverse_from_path(true, true, false, "".as_ref());
+                    for entry in traversal {
                         if let Some(path_in_worktree) = worktree_paths_to_check
                             .iter()
                             .find(|path_to_check| entry.path.ends_with(&path_to_check.path))

crates/vim/src/command.rs

@@ -1492,7 +1492,7 @@ impl OnMatchingLines {
         let mut search = String::new();
         let mut escaped = false;
 
-        while let Some(c) = chars.next() {
+        for c in chars.by_ref() {
             if escaped {
                 escaped = false;
                 // unescape escaped parens

crates/vim/src/normal/increment.rs

@@ -274,9 +274,9 @@ fn find_boolean(snapshot: &MultiBufferSnapshot, start: Point) -> Option<(Range<P
     let mut end = None;
     let mut word = String::new();
 
-    let mut chars = snapshot.chars_at(offset);
+    let chars = snapshot.chars_at(offset);
 
-    while let Some(ch) = chars.next() {
+    for ch in chars {
         if ch.is_ascii_alphabetic() {
             if begin.is_none() {
                 begin = Some(offset);