generating interfaces instead of implenetations

[Coobaha]

Hi @cristianoc

I noticed that most of the time in our codebase we are actually interested more in generating interface files (.d.ts) instead of .gen.tsx. For this we have tsc that generates .gen.js and .d.gen.ts from .gen.ts.

I think it will be amazing if genType will have a new mode that will print .gen.js and .d.gen.ts right away. So that we can just ship reason packages ready to be consumed in any js lib

[cristianoc]

@Coobaha interested in learning more how these look like. Would you add a couple of examples of .gen.js and .d.gen.ts files from simple examples?

[Coobaha]

how I see this mode:

• outputs js (current untyped mode)
• outputs typescript interface files (similar to typescript printer, but slightly different syntax and only types ofc)

I print interface files from ts code with

tsc --emitDeclarationOnly --declaration

We have two steps build for modules that will be consumed as npm packages:

1. output js+tsx with rescript+gentype
2. produce js only output with tsc by transpiling .gen.tsx to .gen.js + .d.gen.ts

example of definitons from gen.tsx https://gist.github.com/Coobaha/d92f549d5d72c54918712ca8c9244e2c

[cristianoc]

Noting down a couple of quick observations:

• There's the question of what do do when importing from TS, the checking code is emitted in the .gen.tsx file.
• Interface files .d.gen.ts seem to behave more liberally. E.g. let you import a type from a non-existing module without giving errors. In general, they might provide fewer sanity checks for the generated code.

[johnridesabike]

I would be interested in this too. I would ideally like to keep a package.json that looks like this:

{
  "exports": {
    ".": {
      "import": "./lib/es6/src/Main.mjs",
      "require": "./lib/js/src/Main.js"
    },
    "./lib/*": "./lib/*",
    "./src/*": "./src/*"
  },
  "main": "lib/js/src/Main.js",
  "module": "lib/es6/src/Main.mjs",
  "types": "types/Main.d.ts"
}

ReScript can manage everything except for the types. To generate the types, I would currently need to compile *.gen.tsx files and then build the *.d.ts files from those. Currently, that also means setting "in-source": true, "suffix": ".bs.js", configuring tsc, and generating a lot of files that are just for generating the final *.d.ts. If this process could be streamlined, that would great.

[gustavopch]

Would TypeScript understand .d.gen.ts? I think .gen.d.ts would be the right extension. Or even .bs.d.ts so that it matches the original JavaScript file generated by the compiler.

[gustavopch]

In case anyone is struggling with this, I was able to generate .d.ts files by hooking the following script into js-post-build option in bsconfig.json:

#!/usr/bin/env bash

bsJsPath="$1"
bsDTsPath="${bsJsPath/bs\.js/bs\.d\.ts}"
genTsxPath="${bsJsPath/bs\.js/gen\.tsx}"
genDTsPath="${bsJsPath/bs\.js/gen\.d\.ts}"

# Generate .gen.d.ts file (note: when tsc receives a path, it'll ignore tsconfig.json)
tsc --skipLibCheck --declaration --emitDeclarationOnly "$(readlink -f "$path")"

# Rename from .gen.d.ts to .bs.d.ts so that someone importing the .bs.js file from
# vanilla JS also gets better IntelliSense
mv -f "$genDTsPath" "$bsDTsPath"

[pd4d10]

Encountered this issue +1. The implementation in gen.tsx file seems not necessary since we already have bs.js shipped.

Is there any plan? I'm glad to help if the objective is clear

[ryyppy]

This repository is being archived. If you feel like the issue still relevant, please re-create it in the compiler repo. Thanks!