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# AWS Lambda Build Configuration

## ESBuild

In Serverless Framework V.4, [esbuild](https://github.com/evanw/esbuild) is included within the Framework for bundling Javascript and Typescript AWS Lambda functions.

By default, if your AWS Lambda handler is using Typescript files directly, the Framework will build your code automagically upon deploy, without a plugin. No configuration is necessary by default.

### Configuration

V.4 introduces a new `build` configuration block, which you can use to customize [esbuild](https://github.com/evanw/esbuild) settings.

```yaml
build:
  esbuild:
    # Enable or Disable bundling the function code and dependencies. (Default: true)
    bundle: true
    # Enable minifying function code. (Default: false)
    minify: false
    # NPM packages to not be bundled
    external:
      - @aws-sdk/client-s3
    # NPM packages to not be bundled, as well as not included in node_modules
    # in the zip file uploaded to Lambda. By default this will be set to aws-sdk
    # if the runtime is set to nodejs16.x or lower or set to @aws-sdk/* if set to nodejs18.x or higher.
    exclude:
      - @aws-sdk/*
    # The packages config, this can be set to override the behavior of external
    # If this is set then all dependencies will be treated as external and not bundled.
    packages: external
    # By default Framework will attempt to build and package all functions concurrently.
    # This property can bet set to a different number if you wish to limit the
    # concurrency of those operations.
    buildConcurrency: 3
    # Enable or configure sourcemaps, can be set to true or to an object with further configuration.
    sourcemap:
      # The sourcemap type to use, options are (inline, linked, or external)
      type: linked
      # Whether to set the NODE_OPTIONS on functions to enable sourcemaps on Lambda
      setNodeOptions: true
```

## Plugin Conflicts

Please note, plugins that build your code will not work unless you opt out of the default build experience. Some of the plugins affected are:

- `serverless-esbuild`
- `serverless-webpack`
- `serverless-plugin-typescript`

The new `build` configuration is customizable by plugins. We will be introducing more features around this soon.