Refactor "New/Edit list" page to avoid setting state in effect (#36753)

app/javascript/mastodon/features/lists/new.tsx

@@ -22,6 +22,7 @@ import { Column } from 'mastodon/components/column';
 import { ColumnHeader } from 'mastodon/components/column_header';
 import { Icon } from 'mastodon/components/icon';
 import { LoadingIndicator } from 'mastodon/components/loading_indicator';
+import type { List } from 'mastodon/models/list';
 import { useAppDispatch, useAppSelector } from 'mastodon/store';
 
 import { messages as membersMessages } from './members';
@@ -72,36 +73,23 @@ const MembersLink: React.FC<{
   );
 };
 
-const NewList: React.FC<{
-  multiColumn?: boolean;
-}> = ({ multiColumn }) => {
+const NewList: React.FC<{ list?: List | null }> = ({ list }) => {
   const dispatch = useAppDispatch();
-  const { id } = useParams<{ id?: string }>();
-  const intl = useIntl();
   const history = useHistory();
 
-  const list = useAppSelector((state) =>
-    id ? state.lists.get(id) : undefined,
-  );
-  const [title, setTitle] = useState('');
-  const [exclusive, setExclusive] = useState(false);
-  const [repliesPolicy, setRepliesPolicy] = useState<RepliesPolicyType>('list');
+  const {
+    id,
+    title: initialTitle = '',
+    exclusive: initialExclusive = false,
+    replies_policy: initialRepliesPolicy = 'list',
+  } = list ?? {};
+
+  const [title, setTitle] = useState(initialTitle);
+  const [exclusive, setExclusive] = useState(initialExclusive);
+  const [repliesPolicy, setRepliesPolicy] =
+    useState<RepliesPolicyType>(initialRepliesPolicy);
   const [submitting, setSubmitting] = useState(false);
 
-  useEffect(() => {
-    if (id) {
-      dispatch(fetchList(id));
-    }
-  }, [dispatch, id]);
-
-  useEffect(() => {
-    if (id && list) {
-      setTitle(list.title);
-      setExclusive(list.exclusive);
-      setRepliesPolicy(list.replies_policy);
-    }
-  }, [setTitle, setExclusive, setRepliesPolicy, id, list]);
-
   const handleTitleChange = useCallback(
     ({ target: { value } }: React.ChangeEvent<HTMLInputElement>) => {
       setTitle(value);
@@ -159,19 +147,6 @@ const NewList: React.FC<{
   }, [history, dispatch, setSubmitting, id, title, exclusive, repliesPolicy]);
 
   return (
-    <Column
-      bindToDocument={!multiColumn}
-      label={intl.formatMessage(id ? messages.edit : messages.create)}
-    >
-      <ColumnHeader
-        title={intl.formatMessage(id ? messages.edit : messages.create)}
-        icon='list-ul'
-        iconComponent={ListAltIcon}
-        multiColumn={multiColumn}
-        showBackButton
-      />
-
-      <div className='scrollable'>
     <form className='simple_form app-form' onSubmit={handleSubmit}>
       <div className='fields-group'>
         <div className='input with_label'>
@@ -264,10 +239,7 @@ const NewList: React.FC<{
 
           <div className='app-form__toggle__toggle'>
             <div>
-                  <Toggle
-                    checked={exclusive}
-                    onChange={handleExclusiveChange}
-                  />
+              <Toggle checked={exclusive} onChange={handleExclusiveChange} />
             </div>
           </div>
         </label>
@@ -285,6 +257,42 @@ const NewList: React.FC<{
         </button>
       </div>
     </form>
+  );
+};
+
+const NewListWrapper: React.FC<{
+  multiColumn?: boolean;
+}> = ({ multiColumn }) => {
+  const intl = useIntl();
+  const dispatch = useAppDispatch();
+  const { id } = useParams<{ id?: string }>();
+  const list = useAppSelector((state) =>
+    id ? state.lists.get(id) : undefined,
+  );
+
+  useEffect(() => {
+    if (id) {
+      dispatch(fetchList(id));
+    }
+  }, [dispatch, id]);
+
+  const isLoading = id && !list;
+
+  return (
+    <Column
+      bindToDocument={!multiColumn}
+      label={intl.formatMessage(id ? messages.edit : messages.create)}
+    >
+      <ColumnHeader
+        title={intl.formatMessage(id ? messages.edit : messages.create)}
+        icon='list-ul'
+        iconComponent={ListAltIcon}
+        multiColumn={multiColumn}
+        showBackButton
+      />
+
+      <div className='scrollable'>
+        {isLoading ? <LoadingIndicator /> : <NewList list={list} />}
       </div>
 
       <Helmet>
@@ -298,4 +306,4 @@ const NewList: React.FC<{
 };
 
 // eslint-disable-next-line import/no-default-export
-export default NewList;
+export default NewListWrapper;