Expose rawHeaders on the response argument to beforeResponse

Author: pimterry

src/rules/requests/request-handler-definitions.ts

@@ -9,7 +9,8 @@ import {
     Headers,
     CompletedRequest,
     CompletedBody,
-    Explainable
+    Explainable,
+    RawHeaders
 } from "../../types";
 
 import { MaybePromise, Replace } from '../../util/type-utils';
@@ -432,11 +433,15 @@ export class FileHandlerDefinition extends Serializable implements RequestHandle
     }
 }
 
+// This is different from CompletedResponse because CompletedResponse is a client request to Mockttp
+// whereas this is a real response from an upstream server that we modify before forwarding.
+// We aim for a similar shape, but they're not exactly the same.
 export interface PassThroughResponse {
     id: string;
     statusCode: number;
     statusMessage?: string;
     headers: Headers;
+    rawHeaders: RawHeaders;
     body: CompletedBody;
 }
 

src/rules/requests/request-handlers.ts

@@ -521,7 +521,8 @@ export class PassThroughHandler extends PassThroughHandlerDefinition {
             const completedRequest = await waitForCompletedRequest(clientReq);
             const modifiedReq = await this.beforeRequest({
                 ...completedRequest,
-                headers: _.clone(completedRequest.headers)
+                headers: _.cloneDeep(completedRequest.headers),
+                rawHeaders: _.cloneDeep(completedRequest.rawHeaders)
             });
 
             if (modifiedReq?.response) {
@@ -768,6 +769,7 @@ export class PassThroughHandler extends PassThroughHandlerDefinition {
                         statusCode: serverStatusCode,
                         statusMessage: serverRes.statusMessage,
                         headers: serverHeaders,
+                        rawHeaders: _.cloneDeep(serverRawHeaders),
                         body: buildBodyReader(body, serverHeaders)
                     });
 

test/integration/proxy.spec.ts

@@ -683,6 +683,32 @@ nodeOnly(() => {
                 expect(response.statusCode).to.equal(200);
             });
 
+            it("should be able to examine a response's raw headers in beforeResponse", async () => {
+                await remoteServer.forGet('/').thenCallback(() => ({
+                    status: 500,
+                    headers: {
+                        'UPPERCASE-HEADER': 'VALUE'
+                    }
+                }));
+
+                await server.forGet(remoteServer.urlFor("/")).thenPassThrough({
+                    beforeResponse: (res) => {
+                        expect(res.headers).to.deep.equal({
+                            'uppercase-header': 'VALUE'
+                        });
+
+                        expect(res.rawHeaders).to.deep.equal([
+                            ['UPPERCASE-HEADER', 'VALUE']
+                        ]);
+
+                        return { status: 200, body: 'all good' };
+                    }
+                });
+
+                let response = await request.get(remoteServer.urlFor("/"));
+                expect(response).to.equal('all good');
+            });
+
             it("should be able to rewrite a response's status", async () => {
                 await remoteServer.forGet('/').thenReply(404);
                 await server.forGet(remoteServer.urlFor("/")).thenPassThrough({