Just about every developer that I meet has one, or more, side-projects that they work on. My primary side project (an Alexa skill called Movie Quiz) has helped me learn several new technologies over the years. Working on this skill has taught me everything from single-table design to pipelines. DynamoDB CI/CD I recently learned about NestJS at work and the power of Inversion of Control and Dependency Injection. It just so happens that someone kindly added Dependency Injection to the framework that I use for my skill. Also, I’ve been having a difficult time getting some updates in the skill through certification, so it seemed like a good time to implement DI and write some unit tests. more Issues with esbuild Esbuild is a super fast typescript bundler. It gains this speed by completely ignoring the typescript. The problem with that is the Dependency Injection that I wanted to use relies on TypeScript Decorators. I had to turn on and in my tsconfig file, but since esbuild just ignores that, all I get are errors. emitDecoratorMetadata experimentalDecorators Slowing Down esbuild The solution was to get a plugin that negated all of the performance gained by ignoring TypeScript. The plugin runs each typescript file through tsc before passing it to esbuild. First, install the package: esbuild-plugin-tsc pnpm install -D esbuild-plugin-tsc Now, import it and pass it into your esbuild configuration. I’m using esbuild with , so the options are a little nested, but you can use plugins directly with esbuild as well. serverless stack import esbuildPluginTsc from 'esbuild-plugin-tsc';
...
const handler = new sst.Function(stack, 'Handler', {
  nodejs: {
    esbuild: {
      plugins: [
        esbuildPluginTsc({
          tsconfigPath: path.join(HANDLER_ROOT, 'tsconfig.json'),
        }),
      ],
    }
  }
}); Use the Right Format In addition to using the plugin, I had to update my esbuild options to create commonjs-formatted output. While this was frustrating to figure out, it was pretty easy to implement. Just setting to . set the format cjs In the serverless stack function, this is done in the configuration: nodejs nodejs: {
  format: 'cjs',
  esbuild: {
    ...
  }
} Summary In this article, you’ve seen how to use decorators in a TypeScript project that’s bundled with esbuild. Hopefully, decorators will be standardized soon and we won’t have to worry about all of this. In the meantime, I hope this article saves a few people from the frustration of getting this to work! Also published here.

The writer was physically present in relevant location(s) to this story. The location is also a prevalent aspect of this story be it news or otherwise.

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