fix(adapter): handle multi value headers in AWS Lambda (#2494)

* Headers can be undefined on ALB

* Delegate headers from multiValueHeaders

* Add test

* Assert header values

* format

* Make multiValueHeaders optional so it can be omitted

* Avoid Object.entries when undefined

* Write tests in runtime_tests

runtime_tests/lambda/index.test.ts

@@ -139,6 +139,13 @@ describe('AWS Lambda Adapter for Hono', () => {
     return c.text('Valid Cookies')
   })
 
+  app.post('/headers', (c) => {
+    if (c.req.header('foo')?.includes('bar')) {
+      return c.json({ message: 'ok' })
+    }
+    return c.json({ message: 'fail' }, 400)
+  })
+
   const handler = handle(app)
 
   const testApiGatewayRequestContext = {
@@ -491,6 +498,100 @@ describe('AWS Lambda Adapter for Hono', () => {
     ])
   })
 
+  describe('headers', () => {
+    describe('single-value headers', () => {
+      it('Should extract single-value headers and return 200 (ALBProxyEvent)', async () => {
+        const event = {
+          body: '{}',
+          httpMethod: 'POST',
+          isBase64Encoded: false,
+          path: '/headers',
+          headers: {
+            host: 'localhost',
+            foo: 'bar',
+          },
+          requestContext: testALBRequestContext,
+        }
+        const apiGatewayResponseV2 = await handler(event)
+        expect(apiGatewayResponseV2.statusCode).toBe(200)
+      })
+
+      it('Should extract single-value headers and return 200 (APIGatewayProxyEvent)', async () => {
+        const apigatewayProxyEvent = {
+          version: '1.0',
+          resource: '/headers',
+          httpMethod: 'POST',
+          headers: {
+            host: 'localhost',
+            foo: 'bar',
+          },
+          path: '/headers',
+          body: null,
+          isBase64Encoded: false,
+          requestContext: testApiGatewayRequestContext,
+        }
+        const apiGatewayResponseV2 = await handler(apigatewayProxyEvent)
+        expect(apiGatewayResponseV2.statusCode).toBe(200)
+      })
+
+      it('Should extract single-value headers and return 200 (APIGatewayProxyEventV2)', async () => {
+        const apigatewayProxyV2Event = {
+          version: '2.0',
+          routeKey: '$default',
+          headers: {
+            host: 'localhost',
+            foo: 'bar',
+          },
+          rawPath: '/headers',
+          rawQueryString: '',
+          requestContext: testApiGatewayRequestContextV2,
+          resource: '/headers',
+          body: null,
+          isBase64Encoded: false,
+        }
+        const apiGatewayResponseV2 = await handler(apigatewayProxyV2Event)
+        expect(apiGatewayResponseV2.statusCode).toBe(200)
+      })
+    })
+
+    describe('multi-value headers', () => {
+      it('Should extract multi-value headers and return 200 (ALBProxyEvent)', async () => {
+        const event = {
+          body: '{}',
+          httpMethod: 'POST',
+          isBase64Encoded: false,
+          path: '/headers',
+          multiValueHeaders: {
+            host: ['localhost'],
+            foo: ['bar'],
+          },
+          requestContext: testALBRequestContext,
+        }
+        const apiGatewayResponseV2 = await handler(event)
+        expect(apiGatewayResponseV2.statusCode).toBe(200)
+      })
+
+      it('Should extract multi-value headers and return 200 (APIGatewayProxyEvent)', async () => {
+        const apigatewayProxyEvent = {
+          version: '1.0',
+          resource: '/headers',
+          httpMethod: 'POST',
+          headers: {},
+          multiValueHeaders: {
+            host: ['localhost'],
+            foo: ['bar'],
+          },
+          path: '/headers',
+          body: null,
+          isBase64Encoded: false,
+          requestContext: testApiGatewayRequestContext,
+        }
+        const apiGatewayResponseV2 = await handler(apigatewayProxyEvent)
+        expect(apiGatewayResponseV2.statusCode).toBe(200)
+      })
+    })
+  })
+
   it('Should handle a POST request and return a 200 response if cookies match (APIGatewayProxyEvent V1 and V2)', async () => {
     const apiGatewayEvent = {
       version: '1.0',

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 +200,25 @@ 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)
+      }
+    }
+  }
+  if (event.multiValueHeaders) {
+    for (const [k, values] of Object.entries(event.multiValueHeaders)) {
+      if (values) {
+        values.forEach((v) => headers.append(k, v))
+      }
     }
   }