Bug 1841200 - Toggle tree expansion with Enter. r=aleca

Differential Revision: https://phabricator.services.mozilla.com/D182708

--HG--
extra : moz-landing-system : lando

mail/base/content/widgets/tree-listbox.js

@@ -198,6 +198,18 @@
             }
             break;
           }
+          case "Enter": {
+            const selected = this.selectedRow;
+            if (!selected?.classList.contains("children")) {
+              return;
+            }
+            if (selected.classList.contains("collapsed")) {
+              this.expandRow(selected);
+            } else {
+              this.collapseRow(selected);
+            }
+            break;
+          }
           default:
             return;
         }

mail/base/test/browser/browser_treeListbox.js

@@ -649,6 +649,17 @@ async function subtestExpandCollapse() {
   checkRowsAreHidden();
   checkSelected(6, "row-3-1-1");
 
+  // Toggle expansion of row 3-1 with Enter key.
+
+  list.selectedIndex = 5;
+  pressKey("row-3-1", "KEY_Enter", "collapsed");
+  checkRowsAreHidden("row-3-1-1", "row-3-1-2");
+  checkSelected(5, "row-3-1");
+
+  pressKey("row-3-1", "KEY_Enter", "expanded");
+  checkRowsAreHidden();
+  checkSelected(5, "row-3-1");
+
   // Same again, with a RTL tree.
 
   info("switching to RTL");