[transactions] Disallow start/finish in a listener

Author: jamesgpearce

src/store.ts

@@ -1186,23 +1186,24 @@ export const createStore: typeof createStoreDecl = (): Store => {
   const transaction = <Return>(
     actions: () => Return,
     doRollback?: DoRollback,
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore void return only occurs internally
   ): Return => {
-    if (transactions == -1) {
-      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
-      // @ts-ignore only occurs internally
-      return;
+    if (transactions != -1) {
+      startTransaction();
+      const result = actions();
+      finishTransaction(doRollback);
+      return result as Return;
     }
-    startTransaction();
-    const result = actions();
-    finishTransaction(doRollback);
-    return result as Return;
   };
 
   const startTransaction = (): Store => {
     if (transactions == 0) {
       callListeners(startTransactionListeners, undefined, false, false);
     }
-    transactions++;
+    if (transactions != -1) {
+      transactions++;
+    }
     return store;
   };
 

test/unit/store-advanced.test.ts

@@ -721,7 +721,7 @@ describe('Transactions', () => {
     expectNoChanges(listener);
   });
 
-  test('Transaction in a listener ignored', () => {
+  test('Transaction in a listener ignored 1', () => {
     listener.listenToCell('/t1/r1/c1', 't1', 'r1', 'c1');
     const listenerTransaction = jest.fn(() => {
       store.setTables({t1: {r1: {c1: 3}}});
@@ -735,6 +735,22 @@ describe('Transactions', () => {
     expect(listenerTransaction).not.toHaveBeenCalled();
   });
 
+  test('Transaction in a listener ignored 2', () => {
+    listener.listenToCell('/t1/r1/c1', 't1', 'r1', 'c1');
+    const listenerTransaction = jest.fn(() => {
+      store.setTables({t1: {r1: {c1: 3}}});
+    });
+    store.addCellListener('t1', 'r1', 'c1', () => {
+      store.startTransaction();
+      listenerTransaction();
+      store.finishTransaction();
+    });
+    store.setTables({t1: {r1: {c1: 2}}});
+    expectChanges(listener, '/t1/r1/c1', {t1: {r1: {c1: 2}}});
+    expectNoChanges(listener);
+    expect(listenerTransaction).toHaveBeenCalledTimes(1);
+  });
+
   test('Adding a peer listener in a listener', () => {
     const listener = jest.fn(() => null);
     store.addCellListener('t1', 'r1', 'c1', () => {