Runtime.ImportModuleError despite having specified the dependencies in package.json

Question

I used '@azure/identity' package for my Lambda function. If I import but doesn't use the module, the Lambda function is error-free, however when I actually use the module by adding this code:

class SharePointFileUploader {
    // private client: Client;
    constructor(
        private tenantId: string, 
        private clientId: string, 
        private clientSecret: string
    ) {
        // // Create credential
        const credential = new identity.ClientSecretCredential(
            this.tenantId, 
            this.clientId, 
            this.clientSecret
        );
}

I encountered this issue when trying to test the function locally use SAM local invoke. 
{"errorType": "Runtime.ImportModuleError", "errorMessage": "Error: Cannot find module '@azure/identity'
Require stack:
- /var/task/statistics.js
- /var/runtime/index.mjs", "trace": ["Runtime.ImportModuleError: Error: Cannot find module '@azure/identity'", "Require stack:", "- /var/task/statistics.js", "- /var/runtime/index.mjs", "    at _loadUserApp (file:///var/runtime/index.mjs:1087:17)", "    at async UserFunction.js.module.exports.load (file:///var/runtime/index.mjs:1119:21)", "    at async start (file:///var/runtime/index.mjs:1282:23)", "    at async file:///var/runtime/index.mjs:1288:1"]}.

This is my dependencies included in the package.json file:
"dependencies": {
    "@aws-cdk/aws-lambda": "^1.203.0",
    "@aws-sdk/client-s3": "^3.698.0",
    "@aws-sdk/client-secrets-manager": "^3.696.0",
    "@azure/identity": "^4.5.0",
    "@microsoft/microsoft-graph-client": "^3.0.7",
    "@types/aws-lambda": "^8.10.145",
    "aws-cdk-lib": "2.168.0",
    "aws-sdk": "^2.1692.0",
    "constructs": "^10.0.0",
    "node-fetch": "^3.3.2"
  },

Can someone please explain why this happened? Thank you so much in advance!

re:Post Agent · Answer

The error you're encountering is likely due to the way Lambda packages and deploys your function. When you're testing locally using SAM (Serverless Application Model), it's trying to simulate the Lambda environment, but it seems that the '@azure/identity' module is not being included in your deployment package.

Here are a few things to check and try:

1. Make sure you've run 'npm install' in your project directory to install all the dependencies listed in your package.json file.

2. When using SAM to test locally, it doesn't automatically include node_modules. You need to ensure that your dependencies are properly packaged. Try running 'sam build' before 'sam local invoke' to package your function correctly.

3. Check if you're using the correct Node.js runtime version that's compatible with all your dependencies.

4. Ensure that your Lambda function's handler is correctly specified in your SAM template (template.yaml or template.json file).

5. If you're using ES modules (indicated by "type": "module" in package.json), make sure your import statements are correct. For CommonJS, use require() instead of import.

6. Try adding a "prepare" script in your package.json to install dependencies:
   "scripts": {
     "prepare": "npm install"
   }

7. If the issue persists, you might need to explicitly include the node_modules in your deployment package. You can do this by modifying your SAM template to include a custom packaging instruction.

Remember, when you deploy to AWS Lambda, you need to include all dependencies in the deployment package. Local testing with SAM should mimic this environment, but sometimes additional configuration is needed to ensure all modules are properly included.  
**Sources**  
[Locally invoke Lambda functions with AWS SAM - AWS Serverless Application Model](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-using-invoke.html)  
[Working with AWS Lambda functions using the AWS Toolkit - AWS Cloud9](https://docs.aws.amazon.com/cloud9/latest/user-guide/lambda-toolkit.html)  
[Troubleshoot deployment issues in Lambda - AWS Lambda](https://docs.aws.amazon.com/lambda/latest/dg/troubleshooting-deployment.html)

Runtime.ImportModuleError despite having specified the dependencies in package.json

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