Debug TypeScript serverless application in VSCode

1. Edit serverless.yml, the handler path should be from the root folder (not dist/**/your_handler.main or from any directory with compiled files), for instance:

   ...
   my_function:
    handler: handlers/my_function.main
   ...

2. Edit serverless.yml adding serverless-plugin-typescript to the plugin section:

   plugins:
     - serverless-plugin-typescript
   ...

3. Install the plugin and some other NPM dependencies:

   $ npm install --save-dev typescript
   $ npm install --save-dev serverless-plugin-typescript
   

4. Edit your launch.json with something like this:

    {
      "version": "0.2.0",
      " configurations": [
        {
          "type": "node",
          "request": "launch",
          "name": "Whatever you want",
          "program": "${workspaceFolder}/node_modules/serverless/bin/serverless",
          "args": [
            "invoke",
            "local",
            "--function",
            "my_function",
            "--path",
            "mocks/my_function.json"
          ],
          "sourceMaps": true,
          "preLaunchTask": "tsc: build - tsconfig.cjs.json",
          "runtimeArgs": ["--lazy"],
          "protocol": "inspector",
          "runtimeExecutable": "node",
          "env": {
          },
        }
      ]
    }

5. Check the VSCode debug console to see if it is working.

Notes:

• Adding "outFiles": ["${workspaceFolder}/dist/**/*.js"] to the launch.json avoid errors like Could not read source map for file://..../node_modules/typescript/lib/typescript.js.map' but it probably won't hit breakpoints.

• More information : https://enrico-portolan.medium.com/debugging-typescript-aws-lambda-with-vscode-and-serverless-967f2a201fab.

• To debug without mocks for instance to invoke endpoints from Postman, edit your launch.json with something like this:

    {
      "version": "0.2.0",
      " configurations": [
        {
          "type": "node",
          "request": "launch",
          "name": "Whatever you want",
          "program": "${workspaceFolder}/node_modules/serverless/bin/serverless",
          "args": ["offline"],
          "sourceMaps": true,
          "preLaunchTask": "tsc: build - tsconfig.cjs.json",
          "runtimeArgs": ["--lazy"],
          "protocol": "inspector",
          "runtimeExecutable": "node",
          "env": {
          },
        }
      ]
    }

  and remove serverless-plugin-typescript from the serverless.yml (also the change all handlers path on the serverless.yml as mentioned before)