Add Headers#getAll by prototype manipulation, closes #73

Author: mrbbot

packages/core/src/plugins/core.ts

@@ -33,11 +33,10 @@ import {
   SetupResult,
   globsToMatcher,
 } from "@miniflare/shared";
-import { File, FormData } from "undici";
+import { File, FormData, Headers } from "undici";
 import {
   DOMException,
   FetchEvent,
-  Headers,
   Request,
   Response,
   ScheduledEvent,

packages/core/src/standards/http.ts

@@ -18,7 +18,6 @@ import type { BusboyHeaders } from "busboy";
 import { Colorize, blue, bold, green, grey, red, yellow } from "kleur/colors";
 import { splitCookiesString } from "set-cookie-parser";
 import {
-  Headers as BaseHeaders,
   Request as BaseRequest,
   RequestInfo as BaseRequestInfo,
   RequestInit as BaseRequestInit,
@@ -27,6 +26,7 @@ import {
   BodyInit,
   File,
   FormData,
+  Headers,
   RequestCache,
   RequestCredentials,
   RequestDestination,
@@ -52,17 +52,24 @@ function makeEnumerable<T>(prototype: any, instance: T, keys: (keyof T)[]) {
   }
 }
 
-export class Headers extends BaseHeaders {
-  getAll(key: string): string[] {
-    if (key.toLowerCase() !== "set-cookie") {
-      throw new TypeError(
-        'getAll() can only be used with the header name "Set-Cookie".'
-      );
-    }
-    const value = super.get("set-cookie");
-    return value ? splitCookiesString(value) : [];
+// Manipulating the prototype like this isn't very nice. However, this is a
+// non-standard function so it's unlikely to cause problems with other people's
+// code. Miniflare is also usually the only thing running in a process.
+// The alternative would probably be to subclass Headers. However, we'd have
+// to construct a version of our Headers object from undici Headers, which
+// would copy the headers. If we then attempted to create a new Response from
+// this mutated-header Response, the headers wouldn't be copied, as we unwrap
+// our hybrid Response before passing it to undici.
+// @ts-expect-error getAll is non-standard
+Headers.prototype.getAll = function (key: string): string[] {
+  if (key.toLowerCase() !== "set-cookie") {
+    throw new TypeError(
+      'getAll() can only be used with the header name "Set-Cookie".'
+    );
   }
-}
+  const value = this.get("set-cookie");
+  return value ? splitCookiesString(value) : [];
+};
 
 // Instead of subclassing our customised Request and Response classes from
 // BaseRequest and BaseResponse, we instead compose them and implement the same
@@ -92,7 +99,6 @@ export class Body<Inner extends BaseRequest | BaseResponse> {
   [kInputGated] = false;
   [kFormDataFiles] = true; // Default to enabling form-data File parsing
   #inputGatedBody?: ReadableStream;
-  #headers?: Headers;
 
   constructor(inner: Inner) {
     this[kInner] = inner;
@@ -108,11 +114,7 @@ export class Body<Inner extends BaseRequest | BaseResponse> {
   }
 
   get headers(): Headers {
-    if (this.#headers) return this.#headers;
-    const headers = new Headers(this[kInner].headers);
-    // @ts-expect-error internal kGuard isn't included in type definitions
-    headers[fetchSymbols.kGuard] = this[kInner].headers[fetchSymbols.kGuard];
-    return (this.#headers = headers);
+    return this[kInner].headers;
   }
 
   get body(): ReadableStream | null {

packages/core/src/standards/index.ts

@@ -4,7 +4,6 @@ export * from "./domexception";
 export * from "./encoding";
 export * from "./event";
 export {
-  Headers,
   Body,
   withInputGating,
   withStringFormDataFiles,

packages/core/test/standards/http.spec.ts

@@ -3,7 +3,6 @@ import { text } from "stream/consumers";
 import { ReadableStream, TransformStream, WritableStream } from "stream/web";
 import {
   Body,
-  Headers,
   IncomingRequestCfProperties,
   Request,
   Response,
@@ -26,26 +25,30 @@ import {
 import { WebSocketPair } from "@miniflare/web-sockets";
 import test, { Macro } from "ava";
 import {
-  Headers as BaseHeaders,
   Request as BaseRequest,
   Response as BaseResponse,
   BodyMixin,
   File,
   FormData,
+  Headers,
 } from "undici";
 
 // @ts-expect-error filling out all properties is annoying
 const cf: IncomingRequestCfProperties = { country: "GB" };
 
 test('Headers: getAll: throws if key not "Set-Cookie"', (t) => {
   const headers = new Headers();
+  // @ts-expect-error getAll is added to the Headers prototype by importing
+  // @miniflare/core
   t.throws(() => headers.getAll("set-biscuit"), {
     instanceOf: TypeError,
     message: 'getAll() can only be used with the header name "Set-Cookie".',
   });
 });
 test("Headers: getAll: returns empty array if no headers", (t) => {
   const headers = new Headers();
+  // @ts-expect-error getAll is added to the Headers prototype by importing
+  // @miniflare/core
   t.deepEqual(headers.getAll("Set-Cookie"), []);
 });
 test("Headers: getAll: returns separated Set-Cookie values", (t) => {
@@ -57,6 +60,8 @@ test("Headers: getAll: returns separated Set-Cookie values", (t) => {
   headers.append("Set-Cookie", cookie2);
   headers.append("Set-Cookie", cookie3);
   t.is(headers.get("set-Cookie"), [cookie1, cookie2, cookie3].join(", "));
+  // @ts-expect-error getAll is added to the Headers prototype by importing
+  // @miniflare/core
   t.deepEqual(headers.getAll("set-CoOkiE"), [cookie1, cookie2, cookie3]);
 });
 
@@ -148,19 +153,6 @@ test(
 );
 test(inputGatedConsumerMacro, "json");
 test(inputGatedConsumerMacro, "text");
-test("Body: reuses custom headers instance", (t) => {
-  const headers = new BaseHeaders();
-  headers.append("Set-Cookie", "key1=value1");
-  headers.append("Set-Cookie", "key2=value2");
-  const body = new Body(new BaseResponse("body", { headers }));
-  const customHeaders = body.headers;
-  t.not(headers, customHeaders);
-  t.is(body.headers, customHeaders);
-  t.deepEqual(customHeaders.getAll("Set-Cookie"), [
-    "key1=value1",
-    "key2=value2",
-  ]);
-});
 test("Body: formData: parses regular form data fields", async (t) => {
   // Check with application/x-www-form-urlencoded Content-Type
   let body = new Body(

packages/http-server/src/index.ts

@@ -171,6 +171,8 @@ export function createRequestListener<Plugins extends HTTPPluginSignatures>(
           key = key.toLowerCase();
           if (key === "set-cookie") {
             // Multiple Set-Cookie headers should be treated as separate headers
+            // @ts-expect-error getAll is added to the Headers prototype by
+            // importing @miniflare/core
             headers["set-cookie"] = response.headers.getAll("set-cookie");
           } else {
             headers[key] = value;