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1.0.38 • Public • Published


Bundles PureScript modules with Rollup

Why Rollup?

Here are the file sizes for the examples/tab-organizer program:

Bundler Unminified JSMin UglifyJS
rollup-plugin-purs 112.2 kB 70.3 kB 35.7 kB
purs bundle 157.8 kB 107.2 kB 65.2 kB
webpack 977.4 kB 654.0 kB 178.8 kB


  1. Add the following to your package.json:

      "rollup": "^0.41.6",
      "rollup-plugin-purs": "^1.0.35"
      "build": "rollup --config"
  2. Run npm install

  3. Place this code into a file called rollup.config.js:

    import purs from "rollup-plugin-purs";
    export default {
      entry: "src/Main.purs",
      dest: "bundle.js",
      format: "iife",
      sourceMap: true,
      plugins: [
  4. This plugin does not compile PureScript code, so you will need to run pulp build -- --source-maps (or equivalent)

  5. Run npm run build

  6. The final bundle is in the bundle.js file. Enjoy the smaller file size and optimizations!

You can see an example program in the examples/pulp init folder.


These are the default options:

  include: undefined,      // Glob pattern for files/directories to include
  exclude: undefined,      // Glob pattern for files/directories to exclude
  buildDir: "output",      // Directory where the `purs compile` files are located
  runMain: true,           // Whether to call the `main` function or not
  debug: true,             // Displays additional warnings and statistics
  optimizations: {
    uncurry: true,         // Whether to apply the uncurrying optimization or not
    inline: true,          // Whether to inline some functions or not
    removeDeadCode: true,  // Whether to remove dead code or not
    assumePureVars: true   // Whether to assume that variable assignment is always pure

The default options should be fine for most use cases.


These are the optimizations which can be turned on or off:

  • uncurry

    Replaces curried functions with uncurried functions, for improved performance and smaller file size.

  • inline

    Inlines some functions, which can increase performance and decrease the file size.

    It also inlines typeclass instance methods when it can. This can dramatically improve performance and reduce the file size.

  • removeDeadCode

    Removes code which is not used. This dramatically reduces the file size.

  • assumePureVars

    When there is a variable assignment like var foo = ... it will assume that the ... is pure. When used in combination with removeDeadCode, this significantly reduces the file size.

    If assumePureVars is false, then rollup-plugin-purs only removes unused variables if it can prove that the variables are pure. But sometimes it won't remove unused variables, because it's not smart enough to realize that the variables are pure.

    If assumePureVars is true, then rollup-plugin-purs will remove all unused variables, even if it can't prove that the variables are pure.

    PureScript variables are always pure, so assumePureVars is safe. But if you do weird things with the FFI, or if you use an unsafe PureScript function, or if you import a JavaScript library, then assumePureVars might break your program.

In addition to the above optimizations, there are some optimizations which are always applied:

  • Constant propagation / folding

Planned optimizations

  • Common subexpression elimination

Comment pragmas

You can disable certain warnings by including a special comment in your code:

// rollup-plugin-purs ignore dynamic exports
// rollup-plugin-purs ignore dynamic require
// rollup-plugin-purs ignore dynamic module

Each comment disables a specific warning.

The comments must be exactly the same as above, and they must be placed at the top-level of your code, with zero spaces to the left of the comment.

Converting from CommonJS to ES6 modules

This package also contains a convert-commonjs program which can be used to convert a file from CommonJS to ES6 modules.

You can run node_modules/.bin/convert-commonjs input.js > output.js which will take the input.js file (which is CommonJS) and will output to the output.js file (which is ES6 modules).






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