fix: ensure multi-selection with single-line copies do not have extra newlines between copied lines.

This change attempts to fix an edge-case with the multi-selection and full-line copy mechanics.

Before this change, when someone used multi-selection (two cursors), and copied two lines (each with empty selections), then two full lines of content would be copied to the clipboard. However, there would an issue with too many newlines (two newlines) in-between the lines of content.

After this change, now when someone does the same operation, the lines of content will only have a single newline between them.

Author: seanstrom

crates/editor/src/editor.rs

@@ -12479,7 +12479,7 @@ impl Editor {
                 for trimmed_range in trimmed_selections {
                     if is_first {
                         is_first = false;
-                    } else {
+                    } else if !is_entire_line {
                         text += "\n";
                     }
                     let mut len = 0;

crates/editor/src/editor_tests.rs

@@ -26922,6 +26922,43 @@ async fn test_copy_line_without_trailing_newline(cx: &mut TestAppContext) {
     cx.assert_editor_state("line1\nline2\nˇ");
 }
 
+#[gpui::test]
+async fn test_multi_selection_copy_with_newline_between_copied_lines(cx: &mut TestAppContext) {
+    init_test(cx, |_| {});
+
+    let mut cx = EditorTestContext::new(cx).await;
+
+    cx.set_state("line1\nline2\nline3\nˇ");
+
+    cx.update_editor(|e, window, cx| {
+        e.change_selections(SelectionEffects::no_scroll(), window, cx, |s| {
+            s.select_display_ranges([
+                DisplayPoint::new(DisplayRow(0), 0)..DisplayPoint::new(DisplayRow(0), 0),
+                DisplayPoint::new(DisplayRow(1), 0)..DisplayPoint::new(DisplayRow(1), 0),
+                DisplayPoint::new(DisplayRow(2), 0)..DisplayPoint::new(DisplayRow(2), 0),
+            ]);
+        });
+    });
+
+    cx.update_editor(|e, window, cx| e.copy(&Copy, window, cx));
+
+    let clipboard_text = cx
+        .read_from_clipboard()
+        .and_then(|item| item.text().as_deref().map(str::to_string));
+
+    assert_eq!(
+        clipboard_text,
+        Some("line1\nline2\nline3\n".to_string()),
+        "Copying multiple lines should include a single newline between lines"
+    );
+
+    cx.set_state("lineA\nˇ");
+
+    cx.update_editor(|e, window, cx| e.paste(&Paste, window, cx));
+
+    cx.assert_editor_state("lineA\nline1\nline2\nline3\nˇ");
+}
+
 #[gpui::test]
 async fn test_end_of_editor_context(cx: &mut TestAppContext) {
     init_test(cx, |_| {});