Join single-line comments with J.

Fixes #8565.

helix-term/src/commands.rs

@@ -4626,6 +4626,15 @@ fn join_selections_impl(cx: &mut Context, select_space: bool) {
     let text = doc.text();
     let slice = text.slice(..);
 
+    let comment_prefixes = doc
+        .language_config()
+        .and_then(|config| config.comment_tokens.as_ref())
+        .map(|pfxs| &pfxs[..])
+        .unwrap_or(&[]);
+    // Sort by length to handle Rust's /// vs //
+    let mut comment_prefixes = Vec::from(comment_prefixes);
+    comment_prefixes.sort_unstable_by_key(|x| std::cmp::Reverse(x.len()));
+
     let mut changes = Vec::new();
 
     for selection in doc.selection(view.id) {
@@ -4641,6 +4650,14 @@ fn join_selections_impl(cx: &mut Context, select_space: bool) {
             let start = line_end_char_index(&slice, line);
             let mut end = text.line_to_char(line + 1);
             end = skip_while(slice, end, |ch| matches!(ch, ' ' | '\t')).unwrap_or(end);
+            let slice_from_end = slice.slice(end..);
+            for pfx in comment_prefixes.iter() {
+                if slice_from_end.starts_with(pfx) {
+                    end += pfx.len();
+                    break;
+                }
+            }
+            end = skip_while(slice, end, |ch| matches!(ch, ' ' | '\t')).unwrap_or(end);
 
             let separator = if end == line_end_char_index(&slice, line + 1) {
                 // the joining line contains only space-characters => don't include a whitespace when joining

helix-term/tests/test/commands.rs

@@ -632,6 +632,22 @@ async fn test_join_selections_space() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread")]
+async fn test_join_selections_comment() -> anyhow::Result<()> {
+    test((
+        indoc! {"\
+            /// #[a|]#bc
+            /// def
+        "},
+        ":lang rust<ret>J",
+        indoc! {"\
+            /// #[a|]#bc def
+        "},
+    ))
+    .await?;
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread")]
 async fn test_read_file() -> anyhow::Result<()> {
     let mut file = tempfile::NamedTempFile::new()?;