feat(fetch-http-handler): add customization option for requestInit

.changeset/dull-tomatoes-wink.md

@@ -0,0 +1,6 @@
+---
+"@smithy/fetch-http-handler": patch
+"@smithy/types": patch
+---
+
+add requestInit options to fetch

packages/fetch-http-handler/src/fetch-http-handler.spec.ts

@@ -9,6 +9,7 @@ let timeoutSpy: jest.SpyInstance<any>;
 
 (global as any).Request = mockRequest;
 (global as any).Headers = jest.fn();
+const globalFetch = global.fetch;
 
 describe(FetchHttpHandler.name, () => {
   beforeEach(() => {
@@ -23,6 +24,10 @@ describe(FetchHttpHandler.name, () => {
     }
   });
 
+  afterAll(() => {
+    global.fetch = globalFetch;
+  });
+
   it("makes requests using fetch", async () => {
     const mockResponse = {
       headers: {
@@ -454,6 +459,73 @@ describe(FetchHttpHandler.name, () => {
     });
   });
 
+  describe("custom requestInit", () => {
+    it("should allow setting cache requestInit", async () => {
+      const mockResponse = {
+        headers: {
+          entries() {
+            return [];
+          },
+        },
+        blob: jest.fn().mockResolvedValue(new Blob()),
+      };
+      const mockFetch = jest.fn().mockResolvedValue(mockResponse);
+      (global as any).fetch = mockFetch;
+
+      const fetchHttpHandler = new FetchHttpHandler({
+        cache: "no-store",
+      });
+
+      await fetchHttpHandler.handle({} as any, {});
+
+      expect(mockRequest.mock.calls[0][1].cache).toBe("no-store");
+    });
+
+    it("should allow setting custom requestInit", async () => {
+      const mockResponse = {
+        headers: {
+          entries() {
+            return [];
+          },
+        },
+        blob: jest.fn().mockResolvedValue(new Blob()),
+      };
+      const mockFetch = jest.fn().mockResolvedValue(mockResponse);
+      (global as any).fetch = mockFetch;
+
+      const fetchHttpHandler = new FetchHttpHandler({
+        requestInit(req) {
+          return {
+            referrer: "me",
+            cache: "reload",
+            headers: {
+              a: "a",
+              b: req.headers.b,
+            },
+          };
+        },
+      });
+
+      await fetchHttpHandler.handle(
+        {
+          headers: {
+            b: "b",
+          },
+        } as any,
+        {}
+      );
+
+      expect(mockRequest.mock.calls[0][1]).toEqual({
+        referrer: "me",
+        cache: "reload",
+        headers: {
+          a: "a",
+          b: "b",
+        },
+      });
+    });
+  });
+
   // The Blob implementation does not implement Blob.text, so we deal with it here.
   async function blobToText(blob: Blob): Promise<string> {
     const reader = new FileReader();

packages/fetch-http-handler/src/fetch-http-handler.ts

@@ -112,7 +112,9 @@ export class FetchHttpHandler implements HttpHandler<FetchHttpHandlerConfig> {
       headers: new Headers(request.headers),
       method: method,
       credentials,
+      cache: this.config!.cache ?? "default",
     };
+
     if (body) {
       requestOptions.duplex = "half";
     }
@@ -127,6 +129,10 @@ export class FetchHttpHandler implements HttpHandler<FetchHttpHandlerConfig> {
       requestOptions.keepalive = keepAlive;
     }
 
+    if (typeof this.config.requestInit === "function") {
+      Object.assign(requestOptions, this.config.requestInit(request));
+    }
+
     let removeSignalEventListener = () => {};
 
     const fetchRequest = new Request(url, requestOptions);

packages/types/src/http/httpHandlerInitialization.ts

@@ -1,6 +1,7 @@
 import type { Agent as hAgent, AgentOptions as hAgentOptions } from "http";
 import type { Agent as hsAgent, AgentOptions as hsAgentOptions } from "https";
 
+import { HttpRequest as IHttpRequest } from "../http";
 import { Logger } from "../logger";
 
 /**
@@ -97,4 +98,30 @@ export interface FetchHttpHandlerOptions {
    * @see https://developer.mozilla.org/en-US/docs/Web/API/Request/credentials
    */
   credentials?: "include" | "omit" | "same-origin" | undefined | string;
+
+  /**
+   * Cache settings for fetch.
+   * @see https://developer.mozilla.org/en-US/docs/Web/API/Request/cache
+   */
+  cache?: "default" | "force-cache" | "no-cache" | "no-store" | "only-if-cached" | "reload";
+
+  /**
+   * An optional function that produces additional RequestInit
+   * parameters for each httpRequest.
+   *
+   * This is applied last via merging with Object.assign() and overwrites other values
+   * set from other sources.
+   *
+   * @example
+   * ```js
+   * new Client({
+   *   requestHandler: {
+   *     requestInit(httpRequest) {
+   *       return { cache: "no-store" };
+   *     }
+   *   }
+   * });
+   * ```
+   */
+  requestInit?: (httpRequest: IHttpRequest) => RequestInit;
 }