Draft: move from hygen to ts-template-strings generator

[fratzinger]

Introduction

Discussed on slack before. This is based on an idea of @daffl to move from hygen to a new generator based on ts & template strings. This was the initial sketch from @daffl, which is the base of this new generator:

import { GeneratorContext, Prompter } from '@feathersjs/cli'
import { join } from 'path'

type Variables {
  name: string
}

export async function prompt (prompter: Prompter) {
  return prompter.prompt([{
    type: 'input',
    name: 'name',
    message: 'What is the name of your app?'
  }])
}

export async function render (context: GeneratorContext<Variables>) {
  const to = join(context.lib, 'app.ts')
  const body =
`
// This is the ${context.name} app
import feathers from '@feathersjs/feathers'

const app = feathers()

export default app
`

  return { body, to }
}

Related: #2414, #2425

Summary

Proof of concept. Moved from hygen with ejs to new custom generator based on ts & template strings. This is 'just' a refactor. Globally spoken, nothing added or changed. It was fairly easy and has a lot in common with hygen. I enjoyed the template strings very much!

I think this could be something!

Things changed:

• added almost all files from @feathersjs/hygen to this repo, and tweaked obviously. (see folder nextgen)
• changed all template files to new ts files with render function
• front-matter attributes become exported members of the render function (see type RenderAttributes)
• prompt.js and index.js files for hygen became prompt.ts and index.ts
• changed (compared to @feathersjs/hygen lazy require() to lazy await import()
• removed dependencies @feathersjs/hygen
• removed (compared to @feathersjs/hygen): dependencies ejs, front-matter
• changed (compared to @feathersjs/hygen): moved from chalk to picocolors and colorize-template cause perf

Benefits:

• full typescript support. type suggestion, auto complete, type checking

Downsides:

• no code formatting in template strings
• escape template strings are little bit annoying:

const body = `
app.listen(port).then(() => {
  logger.info(\`Feathers app listening on http://\${host}:\${port}\`);
});
`

Things to be done:

• There is a bug while generating the custom service in the tests. I looked at it for a while but cannot find the problem. It has to be solved, but doesn't change the proof of concept for now.

Discussion:

David, what do you think? Where to go from this? Do you think it's worth investigating?

I have some thoughts for it and am happy to discuss them:

1. Make it a separate (new) generator (independent from @feathers/cli - like hygen is). Good idea?
2. Add tests for the new generator
3. docs for the generator (new generator and @feathersjs/cli)
4. deno?
5. improve types

[daffl]

This is amazing! I'll have a closer look over the holidays but this looks like it could totally work.

[daffl]

This has been finalized in the first version via #2578