Module transform

[tpluscode]

I don't suppose it is possible to do bundle-time transforms of non-code modules? I would like to have them transformed into ESM so that I can import as code from my project

[gluck]

We support css & json bundling OOB, but we don't allow custom bundle-times transforms for the time being.
Do you have a concrete example of what you trying to achieve ?

[tpluscode]

I would like to serve RDF documents but parsing them in browsers in a constant PITA because most looking depends on large and problematic node libraries and built-ins.

The workaround I have used in the past is to parse the documents at build time and reserialise into JS code which can be processed by RDF libraries.

Here's a loader I recently hacked together for webpack 4

/* eslint-disable @typescript-eslint/no-var-requires */
const { extensions } = require('rdf-utils-fs/defaults')
const { extname } = require('path')
const { parsers } = require('@rdfjs/formats-common')
const toStream = require('string-to-stream')
const Serializer = require('@rdfjs/serializer-rdfjs')

const serializer = new Serializer({
  module: 'esm',
})

function loader(source) {
  const callback = this.async()

  const extension = extname(this.resourcePath).split('.').pop()
  const mediaType = extensions[extension]

  Promise.resolve().then(async () => {
    const quadStream = parsers.import(mediaType, toStream(source))
    const module = serializer.import(quadStream)

    module.on('data', (code) => {
      callback(null, code)
    })
  })
}

module.exports = loader

[gluck]

In case loading RDF at runtime is an option for you, we happen to load RDF libraries in browser pretty fine (we shim most node dependencies, I've just added readable-stream one which we were lacking), e.g.
https://webcomponents.dev/edit/dmZSLw2b506iTg1dNaK3/src/fetchShape.js

Might help for demo purposes.

[tpluscode]

Hm, that's neat. In my original code I used a fetch wrapper library which imports native { promisify } from 'util'.

You must have seen the resulting TypeError: util$d.promisify is not a function error.

Anything I can do about that?

[tpluscode]

By the way, what does it mean that you shimmed readable-stream?

I see two issues with streams now.
They should be async iterable, so that I would write code for await (const quad of formats.parsers.import(type, stream). Not errors with X is not async iterable

I also wanted to revert to @rdf-esm/formats-common which dynamically loads parser modules. Fails with readableStream.PassThrough is not a constructor 🤔

[gluck]

Fixes for the 3 issues are on their way, had to patch readable-stream though: nodejs/readable-stream#348 (comment)

[gluck]

Done!
https://webcomponents.dev/edit/dmZSLw2b506iTg1dNaK3/src/fetchShape.ts

[tpluscode]

You rock!