Fix #1101 and a few refactoring.

Author: MatsuTaku

atcoder-problems-frontend/src/api/APIClient.ts

@@ -323,8 +323,15 @@ export const useVirtualContestSubmissions = (
     return submissionChunks.flatMap((x) => x);
   };
 
+  const custom_key =
+    "useVirtualContestSubmissions&" +
+    (users.length === 0
+      ? "empty"
+      : users.length === 1
+      ? users[0]
+      : "multiuser");
   return useSWRData(
-    "useVirtualContestSubmissions",
+    custom_key,
     () => (users.length > 0 ? fetcher() : Promise.resolve([])),
     {
       refreshInterval,

atcoder-problems-frontend/src/pages/Internal/VirtualContest/ShowContest/ContestTable.tsx

@@ -154,11 +154,11 @@ export const ContestTable = (props: Props) => {
     end,
     props.enableAutoRefresh
   );
-  if (!submissions.data && !submissions.error) {
-    return <Spinner />;
+  if (submissions.error) {
+    return <Alert color="danger">Failed to fetch submissions.</Alert>;
   }
   if (!submissions.data) {
-    return <Alert color="danger">Failed to fetch submissions.</Alert>;
+    return <Spinner />;
   }
 
   const modelArray = consolidateModels(problems, problemMap, problemModels);

atcoder-problems-frontend/src/pages/Internal/VirtualContest/ShowContest/index.tsx

@@ -68,25 +68,22 @@ const Problems = (props: {
 }) => {
   const { alreadyJoined } = props;
   const submissions = useVirtualContestSubmissions(
-    [props.atCoderUserId],
+    alreadyJoined ? [props.atCoderUserId] : [],
     props.problems.map((p) => p.item.id),
     props.start,
     props.end,
     false
   );
   const pointOverrideMap = constructPointOverrideMap(props.problems);
-  const showUserResults =
-    props.atCoderUserId !== "" &&
-    submissions.data !== null &&
-    submissions.data !== undefined;
+  const showUserResults = alreadyJoined && submissions.data;
   const results = submissions.data
     ? reduceUserContestResult(submissions.data, (id) =>
         pointOverrideMap.get(id)
       )
     : new Map<UserId, ReducedProblemResult>();
   const ResultIcon = (props: { id: ProblemId }) => {
     const result = results.get(props.id);
-    if (!alreadyJoined || !result) return null;
+    if (!result) return null;
     if (result.accepted) {
       return <FcCheckmark />;
     } else {
@@ -210,7 +207,7 @@ const Standings = (props: StandingsProps) => {
                 checked={showRating}
                 onChange={(): void => setShowRating(!showRating)}
               />
-              {alreadyJoined && (
+              {alreadyJoined && contestInfo.mode === null && (
                 <CustomInput
                   type="switch"
                   id="pinMe"