Alb multivalueheaders (#272)

* fix: ALB ignore headers property when multi value headers is on

* ensure ret headers are arrays

Author: adrienblot

README.md

@@ -29,9 +29,10 @@ $ npm i @fastify/aws-lambda
 | decorationPropertyName         | The default property name for request decoration                                                                                           | `awsLambda`                        |
 | callbackWaitsForEmptyEventLoop | See: [Official Documentation](https://docs.aws.amazon.com/lambda/latest/dg/nodejs-context.html#nodejs-prog-model-context-properties)       | `undefined`                        |
 | retainStage                    | Retain the stage part of the API Gateway URL                                                                                               | `false`                            |
-| pathParameterUsedAsPath        | Use a defined pathParameter as path (i.e. `'proxy'`)                                                                                               | `false`                            |
-| parseCommaSeparatedQueryParams        | Parse querystring with commas into an array of values. Affects the behavior of the querystring parser with commas while using [Payload Format Version 2.0](https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html#http-api-develop-integrations-lambda.proxy-format)                                                                                               | `true`                            |
-| payloadAsStream        |  If set to true the response is a stream and can be used with `awslambda.streamifyResponse`                                                                                                | `false`                            |
+| pathParameterUsedAsPath        | Use a defined pathParameter as path (i.e. `'proxy'`)                                                                                       | `false`                            |
+| parseCommaSeparatedQueryParams | Parse querystring with commas into an array of values. Affects the behavior of the querystring parser with commas while using [Payload Format Version 2.0](https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html#http-api-develop-integrations-lambda.proxy-format)                                                                                                                       | `true`                             |
+| payloadAsStream                |  If set to true the response is a stream and can be used with `awslambda.streamifyResponse`                                                | `false`                            |
+| albMultiValueHeaders           |  Set to true if using ALB with multi value headers attribute                                                                               | `false`                            |
 ## 📖Example
 
 ### lambda.js

index.js

@@ -19,6 +19,7 @@ module.exports = (app, options) => {
   options.pathParameterUsedAsPath = options.pathParameterUsedAsPath !== undefined ? options.pathParameterUsedAsPath : false
   options.parseCommaSeparatedQueryParams = options.parseCommaSeparatedQueryParams !== undefined ? options.parseCommaSeparatedQueryParams : true
   options.payloadAsStream = options.payloadAsStream !== undefined ? options.payloadAsStream : false
+  options.albMultiValueHeaders = options.albMultiValueHeaders !== undefined ? options.albMultiValueHeaders : false
   let currentAwsArguments = {}
   if (options.decorateRequest) {
     options.decorationPropertyName = options.decorationPropertyName || 'awsLambda'
@@ -80,6 +81,8 @@ module.exports = (app, options) => {
       Object.keys(event.multiValueHeaders).forEach((h) => {
         if (event.multiValueHeaders[h].length > 1) {
           headers[h] = event.multiValueHeaders[h]
+        } else if (event.multiValueHeaders[h].length === 1 && options.albMultiValueHeaders) {
+          headers[h] = event.multiValueHeaders[h][0]
         }
       })
     }
@@ -168,6 +171,12 @@ module.exports = (app, options) => {
 
         if (cookies && event.version === '2.0') ret.cookies = cookies
         if (multiValueHeaders && (!event.version || event.version === '1.0')) ret.multiValueHeaders = multiValueHeaders
+        if (options.albMultiValueHeaders) {
+          if (!ret.multiValueHeaders) ret.multiValueHeaders = {}
+          Object.entries(ret.headers).forEach(([key, value]) => {
+            ret.multiValueHeaders[key] = [value]
+          })
+        }
 
         if (!options.payloadAsStream) {
           ret.body = isBase64Encoded ? res.rawPayload.toString('base64') : res.payload

test/alb.test.js

@@ -214,4 +214,35 @@ describe('ALB Tests', async () => {
     assert.equal(ret.statusCode, 200)
     assert.equal(ret.body, '{"q$":["foo@bar","foo?bar"]}')
   })
+
+  it('GET with multi-value headers', async () => {
+    const app = fastify()
+    app.get('/test', async (request, reply) => {
+      assert.equal(request.headers['x-my-header'], 'wuuusaaa')
+      reply.send({ hello: 'world' })
+    })
+    const proxy = awsLambdaFastify(app, {
+      albMultiValueHeaders: true
+    })
+
+    const ret = await proxy({
+      requestContext: { elb: { targetGroupArn: 'xxx' } },
+      httpMethod: 'GET',
+      path: '/test',
+      multiValueHeaders: {
+        'x-my-header': ['wuuusaaa']
+      }
+    })
+    assert.equal(ret.statusCode, 200)
+    assert.equal(ret.body, '{"hello":"world"}')
+    console.log(JSON.stringify(ret.multiValueHeaders))
+    assert.ok(ret.multiValueHeaders)
+    assert.equal(
+      ret.headers['content-type'],
+      ['application/json; charset=utf-8']
+    )
+    assert.equal(ret.headers['content-length'], ['17'])
+    assert.ok(ret.headers.date)
+    assert.equal(ret.headers.connection, ['keep-alive'])
+  })
 })