fix(aws-lambda): avoid duplicating already set headers (#2585)

* fix: avoid duplicating already set headers

* test: add missing content-type header

src/adapter/aws-lambda/handler.test.ts

@@ -1,4 +1,5 @@
-import { isContentTypeBinary, isContentEncodingBinary } from './handler'
+import type { LambdaEvent } from './handler'
+import { getProcessor, isContentEncodingBinary, isContentTypeBinary } from './handler'
 
 describe('isContentTypeBinary', () => {
   it('Should determine whether it is binary', () => {
@@ -27,3 +28,142 @@ describe('isContentEncodingBinary', () => {
     expect(isContentEncodingBinary('unknown')).toBe(false)
   })
 })
+
+describe('EventProcessor.createRequest', () => {
+  it('Should return valid Request object from version 1.0 API Gateway event', () => {
+    const event: LambdaEvent = {
+      version: '1.0',
+      resource: '/my/path',
+      path: '/my/path',
+      httpMethod: 'GET',
+      headers: {
+        'content-type': 'application/json',
+        header1: 'value1',
+        header2: 'value1',
+      },
+      multiValueHeaders: {
+        header1: ['value1'],
+        header2: ['value1', 'value2', 'value3'],
+      },
+      queryStringParameters: {
+        parameter2: 'value',
+      },
+      multiValueQueryStringParameters: {
+        parameter1: ['value1', 'value2'],
+        parameter2: ['value'],
+      },
+      requestContext: {
+        accountId: '123456789012',
+        apiId: 'id',
+        authorizer: {
+          claims: null,
+          scopes: null,
+        },
+        domainName: 'id.execute-api.us-east-1.amazonaws.com',
+        domainPrefix: 'id',
+        extendedRequestId: 'request-id',
+        httpMethod: 'GET',
+        identity: {
+          sourceIp: '192.0.2.1',
+          userAgent: 'user-agent',
+          clientCert: {
+            clientCertPem: 'CERT_CONTENT',
+            subjectDN: 'www.example.com',
+            issuerDN: 'Example issuer',
+            serialNumber: 'a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1',
+            validity: {
+              notBefore: 'May 28 12:30:02 2019 GMT',
+              notAfter: 'Aug  5 09:36:04 2021 GMT',
+            },
+          },
+        },
+        path: '/my/path',
+        protocol: 'HTTP/1.1',
+        requestId: 'id=',
+        requestTime: '04/Mar/2020:19:15:17 +0000',
+        requestTimeEpoch: 1583349317135,
+        resourcePath: '/my/path',
+        stage: '$default',
+      },
+      pathParameters: {},
+      stageVariables: {},
+      body: null,
+      isBase64Encoded: false,
+    }
+
+    const processor = getProcessor(event)
+    const request = processor.createRequest(event)
+
+    expect(request.method).toEqual('GET')
+    expect(request.url).toEqual(
+      'https://id.execute-api.us-east-1.amazonaws.com/my/path?parameter2=value'
+    )
+    expect(Object.fromEntries(request.headers)).toEqual({
+      'content-type': 'application/json',
+      header1: 'value1',
+      header2: 'value1, value2, value3',
+    })
+  })
+
+  it('Should return valid Request object from version 2.0 API Gateway event', () => {
+    const event: LambdaEvent = {
+      version: '2.0',
+      routeKey: '$default',
+      rawPath: '/my/path',
+      rawQueryString: 'parameter1=value1&parameter1=value2&parameter2=value',
+      cookies: ['cookie1', 'cookie2'],
+      headers: {
+        'content-type': 'application/json',
+        header1: 'value1',
+        header2: 'value1,value2',
+      },
+      queryStringParameters: {
+        parameter1: 'value1,value2',
+        parameter2: 'value',
+      },
+      requestContext: {
+        accountId: '123456789012',
+        apiId: 'api-id',
+        authentication: null,
+        authorizer: {},
+        domainName: 'id.execute-api.us-east-1.amazonaws.com',
+        domainPrefix: 'id',
+        http: {
+          method: 'POST',
+          path: '/my/path',
+          protocol: 'HTTP/1.1',
+          sourceIp: '192.0.2.1',
+          userAgent: 'agent',
+        },
+        requestId: 'id',
+        routeKey: '$default',
+        stage: '$default',
+        time: '12/Mar/2020:19:03:58 +0000',
+        timeEpoch: 1583348638390,
+      },
+      body: 'Hello from Lambda',
+      pathParameters: {
+        parameter1: 'value1',
+      },
+      isBase64Encoded: false,
+      stageVariables: {
+        stageVariable1: 'value1',
+        stageVariable2: 'value2',
+      },
+    }
+
+    const processor = getProcessor(event)
+    const request = processor.createRequest(event)
+
+    expect(request.method).toEqual('POST')
+    expect(request.url).toEqual(
+      'https://id.execute-api.us-east-1.amazonaws.com/my/path?parameter1=value1&parameter1=value2&parameter2=value'
+    )
+    expect(Object.fromEntries(request.headers)).toEqual({
+      'content-type': 'application/json',
+      cookie: 'cookie1; cookie2',
+      header1: 'value1',
+      header2: 'value1,value2',
+    })
+  })
+})

src/adapter/aws-lambda/handler.ts

@@ -205,7 +205,9 @@ abstract class EventProcessor<E extends LambdaEvent> {
     if (event.multiValueHeaders) {
       for (const [k, values] of Object.entries(event.multiValueHeaders)) {
         if (values) {
-          values.forEach((v) => headers.append(k, v))
+          // avoid duplicating already set headers
+          const foundK = headers.get(k)
+          values.forEach((v) => (!foundK || !foundK.includes(v)) && headers.append(k, v))
         }
       }
     }
@@ -318,7 +320,7 @@ const v1Processor = new (class EventV1Processor extends EventProcessor<
   }
 })()
 
-const getProcessor = (event: LambdaEvent): EventProcessor<LambdaEvent> => {
+export const getProcessor = (event: LambdaEvent): EventProcessor<LambdaEvent> => {
   if (isProxyEventV2(event)) {
     return v2Processor
   } else {