feat: add retryIf option (#503)

Author: faizanu94

src/fetch.ts

@@ -55,12 +55,19 @@ export function createFetch(globalOptions: CreateFetchOptions = {}): $Fetch {
       }
 
       const responseCode = (context.response && context.response.status) || 500;
-      if (
-        retries > 0 &&
-        (Array.isArray(context.options.retryStatusCodes)
-          ? context.options.retryStatusCodes.includes(responseCode)
-          : retryStatusCodes.has(responseCode))
-      ) {
+
+      const isRetryableStatus = Array.isArray(context.options.retryStatusCodes)
+        ? context.options.retryStatusCodes.includes(responseCode)
+        : retryStatusCodes.has(responseCode);
+
+      const isConditionalRetry =
+        typeof context.options.retryIf === "function"
+          ? await context.options.retryIf(context)
+          : false;
+
+      const shouldRetry = isRetryableStatus || isConditionalRetry;
+
+      if (retries > 0 && shouldRetry) {
         const retryDelay =
           typeof context.options.retryDelay === "function"
             ? context.options.retryDelay(context)

src/types.ts

@@ -68,6 +68,12 @@ export interface FetchOptions<R extends ResponseType = ResponseType, T = any>
 
   /** Default is [408, 409, 425, 429, 500, 502, 503, 504] */
   retryStatusCodes?: number[];
+
+  /**
+   * Condition to retry the request.
+   * @default false
+   */
+  retryIf?: (context: FetchContext<T, R>) => boolean | Promise<boolean>;
 }
 
 export interface ResolvedFetchOptions<

test/index.test.ts

@@ -344,6 +344,93 @@ describe("ofetch", () => {
     });
   });
 
+  it("retries when retryIf (sync) returns true", async () => {
+    let called = 0;
+    await $fetch(getURL("408"), {
+      retry: 2,
+      retryIf: () => {
+        called++;
+        return true;
+      },
+    }).catch(() => "failed");
+    expect(called).to.equal(3);
+  });
+
+  it("retries when retryIf (async) returns true", async () => {
+    let called = 0;
+    await $fetch(getURL("408"), {
+      retry: 2,
+      retryIf: async () => {
+        called++;
+        return true;
+      },
+    }).catch(() => "failed");
+    expect(called).to.equal(3);
+  });
+
+  it("does not retry when retryIf returns false and status does not match", async () => {
+    let called = 0;
+    await $fetch(getURL("404"), {
+      retry: 2,
+      retryIf: () => {
+        called++;
+        return false;
+      },
+    }).catch(() => "failed");
+    expect(called).to.equal(1);
+  });
+
+  it("retries on matching status even if retryIf returns false", async () => {
+    let called = 0;
+    await $fetch(getURL("408"), {
+      retry: 2,
+      retryIf: () => {
+        called++;
+        return false;
+      },
+    }).catch(() => "failed");
+    expect(called).to.equal(3);
+  });
+
+  it("throws if retryIf throws (consumer error) propagates error to consumer", async () => {
+    let called = 0;
+    await expect(
+      $fetch(getURL("408"), {
+        retry: 2,
+        retryIf: () => {
+          called++;
+          throw new Error("bad predicate");
+        },
+      })
+    ).rejects.toThrow("bad predicate");
+    expect(called).to.equal(1);
+  });
+
+  it("retries when both retryStatusCodes and retryIf allow", async () => {
+    let called = 0;
+    await $fetch(getURL("408"), {
+      retry: 2,
+      retryStatusCodes: [408],
+      retryIf: () => {
+        called++;
+        return true;
+      },
+    }).catch(() => "failed");
+    expect(called).to.equal(3);
+  });
+
+  it("retries when only retryStatusCodes match and retryIf is absent", async () => {
+    let called = 0;
+    await $fetch(getURL("408"), {
+      retry: 2,
+      retryStatusCodes: [408],
+      onResponseError: () => {
+        called++;
+      },
+    }).catch(() => "failed");
+    expect(called).to.equal(3);
+  });
+
   it("deep merges defaultOptions", async () => {
     const _customFetch = $fetch.create({
       query: {