AWS Lambda JS V3调用Secrets Manager报错：command.resolveMiddleware不是函数

问题背景 #

使用版本^3.299.0的@aws-sdk/client-secrets-manager，搭配TypeScript 5.0.2、Node.js 18.x，tsconfig配置如下：

{
  "compilerOptions": {
    "module": "NodeNext",
    "target": "ESNext",
    "noImplicitAny": true,
    "preserveConstEnums": true,
    "outDir": "./dist",
    "sourceMap": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "**/*.spec.ts"]
}

执行密钥查询代码时触发错误：

TypeError: command.resolveMiddleware is not a function
    at SecretsManagerClient.send (/var/task/node_modules/@aws-sdk/smithy-client/dist-cjs/client.js:13:33)
    at getExistingSecret (/var/task/aws/secrets-client.js:35:10)
    at addSecret (/var/task/aws/secrets-client.js:8:12)
    at Runtime.handler (/var/task/index.js:9:29)
    at Runtime.handleOnceNonStreaming (file:///var/runtime/index.mjs:1085:29)

相关代码片段：

const client = new SecretsManagerClient({ region: 'my-region' });

async function getExistingSecret(connectionDetails: ConnectionDetails): Promise<string> {
  console.log('checking if secret exists');
  const command = getCommand(connectionDetails);
  console.log(`GetSecretValueCommand: ${JSON.stringify(command)}`);
  return client
    .send(command) // <----- FAILS HERE
    .catch(() => {
      console.log(`secret does not exist`);
      return null;
    })
    .then((response: GetSecretValueCommandOutput) => {
      console.log(`secret exists arn: ${response.ARN}`);
      return response.ARN;
    });
}


const getCommand = (connectionDetails: ConnectionDetails): GetSecretValueCommand => {
  const body = getCommandRequest(connectionDetails);
  console.log(`GetSecretValueRequest: ${JSON.stringify(body)}`);
  return { input: body } as GetSecretValueCommand;
};


const getCommandRequest = (connectionDetails: ConnectionDetails): GetSecretValueCommandInput => {
  return { SecretId: secretName(connectionDetails) } as GetSecretValueCommandInput;
};

错误原因 #

问题出在getCommand函数：你手动构造了一个带input属性的普通对象，并用类型断言伪装成GetSecretValueCommand，但这并不是真正的命令实例。AWS SDK v3的命令类内部包含resolveMiddleware等核心方法，这些是client.send()执行时必须调用的，手动模拟的对象没有这些方法，因此触发错误。

解决方案 #

必须通过new GetSecretValueCommand(input)的方式创建命令实例，而非手动构造对象。

修复后的代码 #

import { SecretsManagerClient, GetSecretValueCommand, GetSecretValueCommandOutput } from "@aws-sdk/client-secrets-manager";

const client = new SecretsManagerClient({ region: 'my-region' });

async function getExistingSecret(connectionDetails: ConnectionDetails): Promise<string | null> {
  console.log('checking if secret exists');
  const commandInput = getCommandRequest(connectionDetails);
  console.log(`GetSecretValueRequest: ${JSON.stringify(commandInput)}`);
  // 正确实例化GetSecretValueCommand
  const command = new GetSecretValueCommand(commandInput);
  
  try {
    const response: GetSecretValueCommandOutput = await client.send(command);
    console.log(`secret exists arn: ${response.ARN}`);
    return response.ARN;
  } catch (error) {
    console.log(`secret does not exist`);
    return null;
  }
}

const getCommandRequest = (connectionDetails: ConnectionDetails): GetSecretValueCommandInput => {
  return { SecretId: secretName(connectionDetails) };
};

额外优化点 #

1. 移除冗余的getCommand函数，直接在业务逻辑中实例化命令，代码更简洁
2. 用async/await配合try/catch替代then/catch链式调用，逻辑更清晰，符合现代异步代码写法
3. 修正返回值类型：原代码中catch返回null但函数声明为Promise<string>，存在类型不匹配，修复为Promise<string | null>

内容的提问来源于stack exchange，提问作者Alex Agathocleous