From 5e936e267c64f0a64eaf9b8efc7ed68a191f8448 Mon Sep 17 00:00:00 2001
From: Anand Srinivasan <66776129+eco-monk@users.noreply.github.com>
Date: Fri, 14 Apr 2023 08:19:43 +0530
Subject: [PATCH] fix: 503 error fixed when navigating to homepage (#21971)

TL;DR 503 error fixed when navigating to homepage while the editor is
loading.

- `RESET_EDITOR_REQUEST` is an action that removes `currentApplication`
from the `applicationsReducer`.
- When starting the editor, appEngine saga has an action `completeChore`
which reads the `currentApplication` object.
- Now, when we go back to homepage (while the editor is still
initializing)
- `RESET_EDITOR_REQUEST` is dispatched (so `currentApplication` is
cleared)
- the appEngine still runs in the background and tries to read
`currentApplication` throwing an error.

Now we make sure appEngine is cancelled whenever `RESET_EDITOR_REQUEST`
is triggered.

A follow up task to investigate how errors are thrown in app editor
saga: #21972

Fixes #21915


## Media
Before:
https://www.loom.com/share/eae1eeeec04f4b35a9d3be6ea8177b0a

After:
https://www.loom.com/share/09c328f81d8344569c0ff0b7a3d97713
---
 app/client/src/sagas/InitSagas.ts | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/app/client/src/sagas/InitSagas.ts b/app/client/src/sagas/InitSagas.ts
index 27956999e8..72c544d49c 100644
--- a/app/client/src/sagas/InitSagas.ts
+++ b/app/client/src/sagas/InitSagas.ts
@@ -148,10 +148,22 @@ function* updateURLSaga(action: ReduxURLChangeAction) {
   });
 }
 
+function* appEngineSaga(action: ReduxAction<AppEnginePayload>) {
+  yield race({
+    task: call(startAppEngine, action),
+    cancel: take(ReduxActionTypes.RESET_EDITOR_REQUEST),
+  });
+}
+
 export default function* watchInitSagas() {
   yield all([
-    takeLatest(ReduxActionTypes.INITIALIZE_EDITOR, startAppEngine),
-    takeLatest(ReduxActionTypes.INITIALIZE_PAGE_VIEWER, startAppEngine),
+    takeLatest(
+      [
+        ReduxActionTypes.INITIALIZE_EDITOR,
+        ReduxActionTypes.INITIALIZE_PAGE_VIEWER,
+      ],
+      appEngineSaga,
+    ),
     takeLatest(ReduxActionTypes.RESET_EDITOR_REQUEST, resetEditorSaga),
     takeEvery(URL_CHANGE_ACTIONS, updateURLSaga),
   ]);