fix: fetchFromMultipleSources returns errorOccurred only if all sources fail

src/controllers/episodes/getByAniListId/index.ts

@@ -49,7 +49,7 @@ const app = new OpenAPIHono<Env>();
 app.openapi(route, async (c) => {
   const aniListId = Number(c.req.param("aniListId"));
 
-  const { result: episodes, errors } = await fetchFromMultipleSources([
+  const { result: episodes, errorOccurred } = await fetchFromMultipleSources([
     () => {
       const isAnifyEnabled = readEnvVariable<boolean>(c.env, "ENABLE_ANIFY");
       return getEpisodesFromAnify(isAnifyEnabled, aniListId);
@@ -64,7 +64,7 @@ app.openapi(route, async (c) => {
       ),
   ]);
 
-  if (errors?.length > 0) {
+  if (errorOccurred) {
     return c.json(ErrorResponse, { status: 500 });
   }
 

src/controllers/search/index.ts

@@ -39,14 +39,14 @@ app.openapi(route, async (c) => {
   const page = Number(c.req.query("page") ?? 1);
   const limit = Number(c.req.query("limit") ?? 10);
 
-  const { result: response, errors } = await fetchFromMultipleSources([
+  const { result: response, errorOccurred } = await fetchFromMultipleSources([
     () => fetchSearchResultsFromAnilist(query, page, limit),
     () => fetchSearchResultsFromAmvstrm(query, page, limit),
   ]);
 
   if (!response) {
     return c.json({
-      success: (errors ?? []).length === 0,
+      success: !errorOccurred,
       results: [],
       hasNextPage: false,
     });

src/controllers/title/index.ts

@@ -48,12 +48,12 @@ app.openapi(route, async (c) => {
   const aniListId = Number(c.req.query("id"));
   const aniListToken = c.req.header("X-AniList-Token");
 
-  const { result: title, errors } = await fetchFromMultipleSources([
+  const { result: title, errorOccurred } = await fetchFromMultipleSources([
     () => fetchTitleFromAnilist(aniListId, aniListToken ?? undefined),
     () => fetchTitleFromAmvstrm(aniListId),
   ]);
 
-  if (errors?.length > 0) {
+  if (errorOccurred) {
     return c.json(ErrorResponse, { status: 500 });
   }
 

src/libs/fetchFromMultipleSources.spec.ts

@@ -21,8 +21,8 @@ describe("fetchFromMultipleSources", () => {
     expect(result).toEqual(2);
   });
 
-  it("has promises with valid responses, contains no errors", async () => {
-    const { errors } = await fetchFromMultipleSources<number>([
+  it("has promises with valid responses, no error occurred", async () => {
+    const { errorOccurred } = await fetchFromMultipleSources<number>([
       () => Promise.resolve(undefined),
       () => Promise.resolve(null),
       () => Promise.reject(),
@@ -30,28 +30,25 @@ describe("fetchFromMultipleSources", () => {
       () => Promise.resolve(3),
     ]);
 
-    expect(errors).toBeNull();
+    expect(errorOccurred).toBeFalse();
   });
 
-  it("has promises with no valid responses, returns null", async () => {
+  it("has promises that all throw, returns null", async () => {
     const { result } = await fetchFromMultipleSources<number>([
-      () => Promise.resolve(null),
       () => Promise.reject("error"),
-      () => Promise.resolve(undefined),
+      () => Promise.reject(new Error("error")),
     ]);
 
     expect(result).toBeNull();
   });
 
-  it("has promises with no valid responses, contains error", async () => {
-    const { errors } = await fetchFromMultipleSources<number>([
-      () => Promise.resolve(null),
+  it("has promises that all throw, contains error", async () => {
+    const { errorOccurred } = await fetchFromMultipleSources<number>([
       () => Promise.reject("error"),
       () => Promise.reject(new Error("error")),
-      () => Promise.resolve(undefined),
     ]);
 
-    expect(errors).toEqual(["error", new Error("error")]);
+    expect(errorOccurred).toBeTrue();
   });
 
   it("has promises but cache has value, returns cached value", async () => {
@@ -71,7 +68,7 @@ describe("fetchFromMultipleSources", () => {
   });
 
   it("has promises but cache has value, contains no errors", async () => {
-    const { errors } = await fetchFromMultipleSources<number>(
+    const { errorOccurred } = await fetchFromMultipleSources<number>(
       [
         () => Promise.resolve(null),
         () => Promise.reject("error"),
@@ -83,7 +80,7 @@ describe("fetchFromMultipleSources", () => {
       },
     );
 
-    expect(errors).toBeNull();
+    expect(errorOccurred).toBeFalse();
   });
 
   it("has promises, no cached value, no valid response, should not save in cache", async () => {

src/libs/fetchFromMultipleSources.ts

@@ -10,7 +10,7 @@ type OptionalArgs<T> =
 
 interface FetchFromMultipleSourcesResult<T> {
   result: T | null;
-  errors: (Error | string | undefined)[] | null;
+  errorOccurred: boolean;
 }
 
 export async function fetchFromMultipleSources<T>(
@@ -19,21 +19,21 @@ export async function fetchFromMultipleSources<T>(
 ): Promise<FetchFromMultipleSourcesResult<T>> {
   let result = await args?.fetchFromCache?.();
   if (result) {
-    return { result, errors: null };
+    return { result, errorOccurred: false };
   }
 
   if (fetchPromises.length === 0) {
     throw new Error("fetchPromises cannot be empty");
   }
 
-  let errors: Record<number, Error> = {};
+  let errorCount = 0;
   for (let i = 0; i < fetchPromises.length; i++) {
     const promise = fetchPromises[i];
     try {
       result = await promise();
       if (result) break;
     } catch (e) {
-      errors[i] = e as Error;
+      errorCount++;
     }
   }
 
@@ -44,7 +44,6 @@ export async function fetchFromMultipleSources<T>(
   result = result ?? null;
   return {
     result,
-    errors:
-      !result && Object.keys(errors).length > 0 ? Object.values(errors) : null,
+    errorOccurred: errorCount === fetchPromises.length,
   };
 }