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<