Add missing rejection handling for Promises (#7008)

* Add eslint-plugin-promise to detect uncaught rejections

* Move alert generation for errors to actions/alert

* Add missing rejection handling for Promises

* Use catch() instead of onReject on then()

Then it will catches rejection from onFulfilled. This detection can be
disabled by `allowThen` option, though.

app/javascript/mastodon/actions/accounts.js

@@ -103,7 +103,7 @@ export function fetchAccount(id) {
       dispatch(importFetchedAccount(response.data));
     })).then(() => {
       dispatch(fetchAccountSuccess());
-    }, error => {
+    }).catch(error => {
       dispatch(fetchAccountFail(id, error));
     });
   };

app/javascript/mastodon/actions/alerts.js

@@ -1,3 +1,10 @@
+import { defineMessages } from 'react-intl';
+
+const messages = defineMessages({
+  unexpectedTitle: { id: 'alert.unexpected.title', defaultMessage: 'Oops!' },
+  unexpectedMessage: { id: 'alert.unexpected.message', defaultMessage: 'An unexpected error occurred.' },
+});
+
 export const ALERT_SHOW    = 'ALERT_SHOW';
 export const ALERT_DISMISS = 'ALERT_DISMISS';
 export const ALERT_CLEAR   = 'ALERT_CLEAR';
@@ -22,3 +29,21 @@ export function showAlert(title, message) {
     message,
   };
 };
+
+export function showAlertForError(error) {
+  if (error.response) {
+    const { data, status, statusText } = error.response;
+
+    let message = statusText;
+    let title   = `${status}`;
+
+    if (data.error) {
+      message = data.error;
+    }
+
+    return showAlert(title, message);
+  } else {
+    console.error(error);
+    return showAlert(messages.unexpectedTitle, messages.unexpectedMessage);
+  }
+}

app/javascript/mastodon/actions/compose.js

@@ -1,11 +1,12 @@
 import api from '../api';
-import { CancelToken } from 'axios';
+import { CancelToken, isCancel } from 'axios';
 import { throttle } from 'lodash';
 import { search as emojiSearch } from '../features/emoji/emoji_mart_search_light';
 import { tagHistory } from '../settings';
 import { useEmoji } from './emojis';
 import { importFetchedAccounts } from './importer';
 import { updateTimeline } from './timelines';
+import { showAlertForError } from './alerts';
 
 let cancelFetchComposeSuggestionsAccounts;
 
@@ -291,6 +292,10 @@ const fetchComposeSuggestionsAccounts = throttle((dispatch, getState, token) =>
   }).then(response => {
     dispatch(importFetchedAccounts(response.data));
     dispatch(readyComposeSuggestionsAccounts(token, response.data));
+  }).catch(error => {
+    if (!isCancel(error)) {
+      dispatch(showAlertForError(error));
+    }
   });
 }, 200, { leading: true, trailing: true });
 

app/javascript/mastodon/actions/lists.js

@@ -1,5 +1,6 @@
 import api from '../api';
 import { importFetchedAccounts } from './importer';
+import { showAlertForError } from './alerts';
 
 export const LIST_FETCH_REQUEST = 'LIST_FETCH_REQUEST';
 export const LIST_FETCH_SUCCESS = 'LIST_FETCH_SUCCESS';
@@ -236,7 +237,7 @@ export const fetchListSuggestions = q => (dispatch, getState) => {
   api(getState).get('/api/v1/accounts/search', { params }).then(({ data }) => {
     dispatch(importFetchedAccounts(data));
     dispatch(fetchListSuggestionsReady(q, data));
-  });
+  }).catch(error => dispatch(showAlertForError(error)));
 };
 
 export const fetchListSuggestionsReady = (query, accounts) => ({

app/javascript/mastodon/actions/push_notifications/registerer.js

@@ -116,14 +116,11 @@ export function register () {
             pushNotificationsSetting.remove(me);
           }
 
-          try {
-            getRegistration()
-              .then(getPushSubscription)
-              .then(unsubscribe);
-          } catch (e) {
-
-          }
-        });
+          return getRegistration()
+            .then(getPushSubscription)
+            .then(unsubscribe);
+        })
+        .catch(console.warn);
     } else {
       console.warn('Your browser does not support Web Push Notifications.');
     }
@@ -143,6 +140,6 @@ export function saveSettings() {
       if (me) {
         pushNotificationsSetting.set(me, data);
       }
-    });
+    }).catch(console.warn);
   };
 }

app/javascript/mastodon/actions/settings.js

@@ -1,5 +1,6 @@
 import api from '../api';
 import { debounce } from 'lodash';
+import { showAlertForError } from './alerts';
 
 export const SETTING_CHANGE = 'SETTING_CHANGE';
 export const SETTING_SAVE   = 'SETTING_SAVE';
@@ -23,7 +24,9 @@ const debouncedSave = debounce((dispatch, getState) => {
 
   const data = getState().get('settings').filter((_, path) => path !== 'saved').toJS();
 
-  api(getState).put('/api/web/settings', { data }).then(() => dispatch({ type: SETTING_SAVE }));
+  api(getState).put('/api/web/settings', { data })
+    .then(() => dispatch({ type: SETTING_SAVE }))
+    .catch(error => dispatch(showAlertForError(error)));
 }, 5000, { trailing: true });
 
 export function saveSettings() {