Fix mangling responses

src/interceptor/NodeClientRequest.ts

@@ -12,6 +12,7 @@ import { IsomorphicRequest } from './utils/IsomorphicRequest';
 import { getArrayBuffer } from './utils/bufferUtils';
 import { isInterceptable } from './utils/isInterceptable';
 import { IsomorphicResponse } from './utils/IsomorphicResponse';
+import { cloneIncomingMessage } from './utils/cloneIncomingMessage';
 
 export type NodeClientOptions = {
   emitter: EventEmitter;
@@ -106,7 +107,12 @@ export class NodeClientRequest extends ClientRequest {
   emit(event: 'pipe', src: Readable): boolean;
   emit(event: 'unpipe', src: Readable): boolean;
   emit(event: string | symbol, ...args: any[]): boolean {
+
     if (event === 'response') {
+      const response = args[0] as IncomingMessage;
+      const firstClone = cloneIncomingMessage(response);
+      const secondClone = cloneIncomingMessage(response);
+
       async function emitResponse(
         requestId: string,
         message: IncomingMessage,
@@ -119,12 +125,10 @@ export class NodeClientRequest extends ClientRequest {
       }
 
       if (this.isInterceptable) {
-        emitResponse(this.requestId as string, args[0], this.emitter);
+        emitResponse(this.requestId as string, secondClone, this.emitter);
       }
 
-      if (this.isInterceptable) {
-        emitResponse(this.requestId as string, args[0], this.emitter);
-      }
+      return super.emit(event as string, firstClone, ...args.slice(1));
     }
 
     return super.emit(event as string, ...args);

src/interceptor/utils/cloneIncomingMessage.ts

@@ -0,0 +1,74 @@
+import { IncomingMessage } from 'http'
+import { PassThrough } from 'stream'
+
+export const IS_CLONE = Symbol('isClone')
+
+export interface ClonedIncomingMessage extends IncomingMessage {
+  [IS_CLONE]: boolean
+}
+
+/**
+ * Clones a given `http.IncomingMessage` instance.
+ */
+export function cloneIncomingMessage(
+  message: IncomingMessage
+): ClonedIncomingMessage {
+  const clone = message.pipe(new PassThrough())
+
+  // Inherit all direct "IncomingMessage" properties.
+  inheritProperties(message, clone)
+
+  // Deeply inherit the message prototypes (Readable, Stream, EventEmitter, etc.).
+  const clonedPrototype = Object.create(IncomingMessage.prototype)
+  getPrototypes(clone).forEach((prototype) => {
+    inheritProperties(prototype, clonedPrototype)
+  })
+  Object.setPrototypeOf(clone, clonedPrototype)
+
+  Object.defineProperty(clone, IS_CLONE, {
+    enumerable: true,
+    value: true,
+  })
+
+  return clone as unknown as ClonedIncomingMessage
+}
+
+/**
+ * Returns a list of all prototypes the given object extends.
+ */
+function getPrototypes(source: object): object[] {
+  const prototypes: object[] = []
+  let current = source
+
+  while ((current = Object.getPrototypeOf(current))) {
+    prototypes.push(current)
+  }
+
+  return prototypes
+}
+
+/**
+ * Inherits a given target object properties and symbols
+ * onto the given source object.
+ * @param source Object which should acquire properties.
+ * @param target Object to inherit the properties from.
+ */
+function inheritProperties(source: object, target: object): void {
+  const properties = [
+    ...Object.getOwnPropertyNames(source),
+    ...Object.getOwnPropertySymbols(source),
+  ]
+
+  for (const property of properties) {
+    if (target.hasOwnProperty(property)) {
+      continue
+    }
+
+    const descriptor = Object.getOwnPropertyDescriptor(source, property)
+    if (!descriptor) {
+      continue
+    }
+
+    Object.defineProperty(target, property, descriptor)
+  }
+}