rollup-plugin-preval

compile-time eval for rollup

performant:
eval static expressions at compile time
allow shorter load times for client

readable:
avoid "magic numbers"
colocate "all the code" in one place

powerful:
use any node package on compile time

license = CC0-1.0 = public domain
warranty = none

install

npm install -D https://github.com/milahu/rollup-plugin-preval.git

config

merge this with your rollup.config.js

import { preval } from 'rollup-plugin-preval';

export default {
  plugins: [
    preval({ basedir: __dirname }), // directory of rollup.config.js
  ],
};

use sample

// preval object
let testPrevalObj = preval(() => ({
  a: Math.PI * 0.5,
  b: Math.sqrt(2),
}));

// result
let testPrevalObj = {
  a: 1.5707963267948966,
  b: 1.4142135623730951
};

using modules

yes you can use modules inside the preval code

let testPreval = preval(() => {
  const fs = require('fs');
  return fs.readFileSync('input.txt').toString();
});

using modules with relative paths

require works relative to the directory of rollup-plugin-preval.js, so

let res = preval(() => require('./src/script.js').someProp);

will try to require node_modules/rollup-plugin-preval/src/src/script.js

you could fix that with a relative path like ../../../src/script.js
but this is not portable
for example this breaks with pnpm package manager
cos symlinks are unidirectional and ../../../ is the pnpm global store

better solution: use absolute paths

in your rollup.config.js set

        preval({
          basedir: __dirname, // directory of rollup.config.js
        }),

and in your script use

let res = preval(({basedir}) => require(basedir+'/src/script.js').someProp);