使用CDK TypeScript Lambda导入常量设置Headers触发无效响应错误

场景说明 #

用CDK TypeScript构建Lambda栈并对接API Gateway，直接在返回对象内定义跨域响应头时功能正常，但将Headers提取为公共常量导入使用时，Lambda启动失败。

正常工作的代码 #

const res = await request<ResponseModel>(req);
return {
    statusCode: res.status,
    headers: {
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Credentials': true
    },
    body: JSON.stringify(res.data)
};

报错的代码示例 #

公共常量文件 common-headers.ts #

export const CommonResponseHeaders = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Credentials': true
};

Lambda函数文件 function.ts #

import { CommonResponseHeaders } from '../../common/common-headers';

const res = await request<ResponseModel>(req);
return {
    statusCode: res.status,
    headers: CommonResponseHeaders,
    body: JSON.stringify(res.data)
};

CDK栈定义 stack.ts #

const function = {
    name: 'myFunction',
    runtime: Runtime.NODEJS_14_X,
    entry: path.join(__dirname, './function.ts'),
    vpcSubnets: {
      subnetType: SubnetType.PRIVATE_WITH_EGRESS
    },
    handler: 'handler',
    environment: {
      ...SomeDefaultVariables
    }
  }
const lambda = new NodejsFunction(this, function.name, function);
const functionUrl = lambda.addFunctionUrl({
authType: FunctionUrlAuthType.NONE,
cors: {
  allowedOrigins: ['*'],
}
});
new CfnOutput(this, `${function.name}-FunctionUrl`, {
value: functionUrl.url,
});

错误信息 #

Invalid lambda response received: Invalid API Gateway Response Keys:
{'trace', 'errorType', 'errorMessage'} in {'errorType': 'TypeError',
'errorMessage': "Cannot read property 'trim' of undefined", 'trace':
["TypeError: Cannot read property 'trim' of undefined", ' at
Object. (/var/task/index.js:10924:40)', ' at
Module._compile (internal/modules/cjs/loader.js:1085:14)', ' at
Object.Module._extensions..js
(internal/modules/cjs/loader.js:1114:10)', ' at Module.load
(internal/modules/cjs/loader.js:950:32)', ' at
Function.Module._load (internal/modules/cjs/loader.js:790:12)', '

at Module.require (internal/modules/cjs/loader.js:974:19)', ' at
require (internal/modules/cjs/helpers.js:101:18)', ' at
_tryRequireFile (/var/runtime/UserFunction.js:72:32)', ' at _tryRequire (/var/runtime/UserFunction.js:160:20)', ' at _loadUserApp (/var/runtime/UserFunction.js:219:12)']}

解决方案 #

1. 修复关键字变量名错误 #

stack.ts中使用了JavaScript保留字function作为变量名，这会直接导致编译失败，是引发错误的核心原因之一。修改变量名：

// stack.ts
const functionConfig = { // 将变量名从function改为functionConfig
    name: 'myFunction',
    runtime: Runtime.NODEJS_14_X,
    entry: path.join(__dirname, './function.ts'),
    vpcSubnets: {
      subnetType: SubnetType.PRIVATE_WITH_EGRESS
    },
    handler: 'handler',
    environment: {
      ...SomeDefaultVariables
    }
  }
const lambda = new NodejsFunction(this, functionConfig.name, functionConfig);

2. 统一响应头值类型 #

API Gateway要求响应头的值必须为字符串类型，直接定义时布尔值true会被隐式转换，但作为常量导入时可能无法自动转换。修改公共常量：

// common-headers.ts
export const CommonResponseHeaders = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Credentials': 'true' // 改为字符串类型
};

3. 验证文件导入路径 #

确认function.ts中../../common/common-headers的路径正确，确保common-headers.ts存在于对应目录下，避免因文件找不到导致的加载错误。

4. 清理缓存重新部署 #

CDK构建缓存可能导致旧代码残留，执行以下命令清理后重新部署：

cdk clean && cdk deploy

内容的提问来源于stack exchange，提问作者noamyg