PklTypescript Example: Express server

This is an example of a simple TypeScript program that uses Pkl for configuration.

Hand-written code

A summary of each of the files in this directory, and what they do:

• index.ts: contains the source code of the express app
• ConfigSchema.pkl: contains the schema of the configuration (just the properties and their types, but not any values)
• config.dev.pkl: amends ConfigSchema.pkl, adding the config values that would be used in local development
• config.prod.pkl: amends ConfigSchema.pkl but with values to be used in production

Generated code

There is also another directory, generated, that contains .pkl.ts files that were generated by pkl-gen-typescript based on the given schema.

The package.json has a script, titled gen-config (but the script name doesn't matter), that executes the following:

pkl-gen-typescript ./ConfigSchema.pkl -o ./generated

This uses the pkl-gen-typescript CLI, passing in ConfigSchema.pkl as the Pkl module to be evaluated, and outputting the generated TypeScript files to the ./generated directory.

Running the app

1. Run npm install in this directory to install dependencies (including a local link to the pkl-typescript project at the root of this repo)
2. Run npm run gen-config to make sure the generated .pkl.ts files in the ./generated directory are up-to-date
3. Run npm run start to start the local dev server

Then, in another terminal, run curl localhost:3003 to see a response from your Pkl-configured Express server.