fix(adapter): handle multi value headers in AWS Lambda

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

@@ -1,4 +1,6 @@
-import { isContentTypeBinary, isContentEncodingBinary } from './handler'
+import { Hono } from '../../hono'
+import { isContentTypeBinary, isContentEncodingBinary, handle } from './handler'
+import type { ALBProxyEvent } from './handler'
 
 describe('isContentTypeBinary', () => {
   it('Should determine whether it is binary', () => {
@@ -27,3 +29,69 @@ describe('isContentEncodingBinary', () => {
     expect(isContentEncodingBinary('unknown')).toBe(false)
   })
 })
+
+describe('handle', () => {
+  const dummyLambdaContext = {
+    awsRequestId: '',
+    callbackWaitsForEmptyEventLoop: false,
+    functionName: '',
+    functionVersion: '',
+    invokedFunctionArn: '',
+    logGroupName: '',
+    logStreamName: '',
+    memoryLimitInMB: '',
+    getRemainingTimeInMillis(): number {
+      return 0
+    },
+  }
+
+  describe('ALB', () => {
+    const app = new Hono().post('/', (c) => {
+      if (c.req.header('foo')?.includes('bar')) {
+        return c.json({ message: 'ok' })
+      }
+      return c.json({ message: 'fail' }, 400)
+    })
+    const handler = handle(app)
+
+    it('Should accept single value headers', async () => {
+      const event: ALBProxyEvent = {
+        body: '{}',
+        httpMethod: 'POST',
+        isBase64Encoded: false,
+        path: '/',
+        headers: {
+          host: 'localhost',
+          foo: 'bar',
+        },
+        requestContext: {
+          elb: {
+            targetGroupArn: '',
+          },
+        },
+      }
+      const response = await handler(event, dummyLambdaContext)
+      expect(response?.['statusCode']).toEqual(200)
+    })
+
+    it('Should accept multi value headers', async () => {
+      const event: ALBProxyEvent = {
+        body: '{}',
+        httpMethod: 'POST',
+        isBase64Encoded: false,
+        path: '/',
+        multiValueHeaders: {
+          host: ['localhost'],
+          foo: ['bar', 'buz'],
+        },
+        requestContext: {
+          elb: {
+            targetGroupArn: '',
+          },
+        },
+      }
+      const response = await handler(event, dummyLambdaContext)
+      expect(response?.['statusCode']).toEqual(200)
+    })
+  })
+})

src/adapter/aws-lambda/handler.ts

@@ -22,6 +22,7 @@ export interface APIGatewayProxyEventV2 {
   version: string
   routeKey: string
   headers: Record<string, string | undefined>
+  multiValueHeaders?: undefined
   cookies?: string[]
   rawPath: string
   rawQueryString: string
@@ -63,7 +64,8 @@ export interface APIGatewayProxyEvent {
 // When calling Lambda through an Application Load Balancer
 export interface ALBProxyEvent {
   httpMethod: string
-  headers: Record<string, string | undefined>
+  headers?: Record<string, string | undefined>
+  multiValueHeaders?: Record<string, string[] | undefined>
   path: string
   body: string | null
   isBase64Encoded: boolean
@@ -198,16 +200,24 @@ const createRequest = (event: LambdaEvent) => {
   const domainName =
     event.requestContext && 'domainName' in event.requestContext
       ? event.requestContext.domainName
-      : event.headers['host']
+      : event.headers?.['host'] ?? event.multiValueHeaders?.['host']?.[0]
   const path = isProxyEventV2(event) ? event.rawPath : event.path
   const urlPath = `https://${domainName}${path}`
   const url = queryString ? `${urlPath}?${queryString}` : urlPath
 
   const headers = new Headers()
   getCookies(event, headers)
-  for (const [k, v] of Object.entries(event.headers)) {
-    if (v) {
-      headers.set(k, v)
+  if (event.headers) {
+    for (const [k, v] of Object.entries(event.headers)) {
+      if (v) {
+        headers.set(k, v)
+      }
+    }
+  } else if (event.multiValueHeaders) {
+    for (const [k, values] of Object.entries(event.multiValueHeaders)) {
+      if (values) {
+        values.forEach((v) => headers.append(k, v))
+      }
     }
   }