editor: Don't overwrite primary selection with only empty cursors

With several cursors and nothing selected, the per-selection text joined
into a string of newlines, which passed the `!text.is_empty()` check and
replaced the primary selection on every keystroke and cursor move.

Only write to the primary selection when at least one selection is
non-empty.

Closes #64446

crates/editor/src/editor_tests.rs

@@ -10996,6 +10996,37 @@ async fn test_copy_and_paste_non_empty_selection_followed_by_empty_selection(
     "});
 }
 
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+#[gpui::test]
+async fn test_empty_cursors_do_not_overwrite_primary_selection(cx: &mut TestAppContext) {
+    init_test(cx, |_| {});
+
+    let mut cx = EditorTestContext::new(cx).await;
+    cx.update(|_, cx| cx.write_to_primary(ClipboardItem::new_string("primary".into())));
+
+    cx.set_state(indoc! {"
+        oneˇ
+        twoˇ
+        threeˇ
+    "});
+    assert_eq!(
+        cx.update(|_, cx| cx.read_from_primary())
+            .and_then(|item| item.text()),
+        Some("primary".to_string())
+    );
+
+    cx.set_state(indoc! {"
+        «oneˇ»
+        twoˇ
+        three
+    "});
+    assert_eq!(
+        cx.update(|_, cx| cx.read_from_primary())
+            .and_then(|item| item.text()),
+        Some("one\n".to_string())
+    );
+}
+
 #[gpui::test]
 async fn test_copy_trim(cx: &mut TestAppContext) {
     init_test(cx, |_| {});

crates/editor/src/selection.rs

@@ -1562,7 +1562,9 @@ impl Editor {
                 }
             }
 
-            if !text.is_empty() {
+            // Several empty cursors still join into a string of newlines, so
+            // check the selections themselves rather than the joined text.
+            if selections.iter().any(|selection| !selection.is_empty()) {
                 cx.write_to_primary(ClipboardItem::new_string(text));
             }
         }