feat: support retryDelay with callback function (#372)

src/fetch.ts

@@ -62,7 +62,9 @@ export function createFetch(globalOptions: CreateFetchOptions = {}): $Fetch {
  ? context.options.retryStatusCodes.includes(responseCode)
  : retryStatusCodes.has(responseCode))
  ) {
- const retryDelay = context.options.retryDelay || 0;
+ const retryDelay = typeof context.options.retryDelay === 'function' ?
+ context.options.retryDelay(context) :
+ context.options.retryDelay || 0;
  if (retryDelay > 0) {
  await new Promise((resolve) => setTimeout(resolve, retryDelay));
  }

src/types.ts

@@ -53,7 +53,7 @@ export interface FetchOptions<R extends ResponseType = ResponseType>
 
  retry?: number | false;
  /** Delay between retries in milliseconds. */
- retryDelay?: number;
+ retryDelay?: number | ((context: FetchContext) => number);
  /** Default is [408, 409, 425, 429, 500, 502, 503, 504] */
  retryStatusCodes?: number[];
 

test/index.test.ts

@@ -273,7 +273,7 @@ describe("ofetch", () => {
  expect(error.request).to.equal(getURL("404"));
  });
 
- it("retry with delay", async () => {
+ it("retry with number delay", async () => {
  const slow = $fetch<string>(getURL("408"), {
  retry: 2,
  retryDelay: 100,
@@ -287,6 +287,20 @@ describe("ofetch", () => {
  expect(race).to.equal("fast");
  });
 
+ it("retry with callback delay", async () => {
+ const slow = $fetch<string>(getURL("408"), {
+ retry: 2,
+ retryDelay: () => 100,
+ }).catch(() => "slow");
+ const fast = $fetch<string>(getURL("408"), {
+ retry: 2,
+ retryDelay: () => 1,
+ }).catch(() => "fast");
+
+ const race = await Promise.race([slow, fast]);
+ expect(race).to.equal("fast");
+ });
+
  it("abort with retry", () => {
  const controller = new AbortController();
  async function abortHandle() {