[transactions] Add transaction listener stats

Author: jamesgpearce

src/store.d.ts

@@ -596,6 +596,10 @@ export type StoreListenerStats = {
    * The number of InvalidCellListeners registered with the Store.
    */
   invalidCell?: number;
+  /**
+   * The number of TransactionListeners registered with the Store.
+   */
+  transaction?: number;
 };
 
 /**

src/store.ts

@@ -965,6 +965,7 @@ export const createStore: typeof createStoreDecl = (): Store => {
           cellIds: collPairSize(cellIdsListeners, collSize3),
           cell: collPairSize(cellListeners, collSize4),
           invalidCell: collPairSize(invalidCellListeners, collSize4),
+          transaction: collPairSize(finishTransactionListeners),
         }
       : {};
 

test/unit/store-advanced.test.ts

@@ -694,6 +694,7 @@ describe('Stats', () => {
       cellIds: 0,
       cell: 0,
       invalidCell: 0,
+      transaction: 0,
     };
   });
 
@@ -723,5 +724,20 @@ describe('Stats', () => {
       expectedListenerStats[thing] = 0;
       expect(store.getListenerStats()).toEqual(expectedListenerStats);
     });
+    test.each([['willFinishTransaction'], ['didFinishTransaction']])(
+      '%s',
+      (thing) => {
+        const addListener =
+          'add' + thing[0].toUpperCase() + thing.substr(1) + 'Listener';
+        expect(((store as any)[addListener] as any)((): null => null)).toEqual(
+          '0',
+        );
+        expectedListenerStats.transaction = 1;
+        expect(store.getListenerStats()).toEqual(expectedListenerStats);
+        store.delListener('0');
+        expectedListenerStats.transaction = 0;
+        expect(store.getListenerStats()).toEqual(expectedListenerStats);
+      },
+    );
   });
 });