svelterollupjsshoelace

Slow rollup.js bundling after copying in a 3rd-party library

I'm using https://shoelace.style (in my Svelte project), and following the example config in shoelace docs, I added a copy() plugin to my rollup.config.js, copying it to public/vendor/shoelace:

export default {
  // SNIP
  plugins: [
    // SNIP
    copy({
      targets: [
        {
          src: path.resolve(
            __dirname,
            "node_modules/@shoelace-style/shoelace/dist/assets"
          ),
          dest: path.resolve(__dirname, "public/vendor/shoelace"),
        },
      ],
    }),
    // SNIP
  ],
};

It works, but now the build takes really really long - upwards of 40s, including incremental rebuilds on file change. I am fairly sure the time loss isn't because it's accidentally copied every time, as the asset folder is just 6M.

So, I suppose there's some tree-shaking and/or optimizations going on? Is there way to exclude the folder from rollup processing - or to troubleshoot/profile the bundling process anyhow?

(If necessary, I can also post the rest of the config; but it's otherwise standard new app template obtained by npx degit sveltejs/template and adding/removing the copy plugin made all the difference.)

Solution

  • The issue turned out to be in the rollup-plugin-copy. Even setting copyOnce: true did not change the behavior, but setting it so that it only copies at the last possible opportunity - the closeBundle hook fixed my problem.

        copy({
      copyOnce: true, // ???
      hook: "closeBundle",
      targets: [
        {
          src: path.resolve(
            __dirname,
            "node_modules/@shoelace-style/shoelace/dist/assets"
          ),
          dest: path.resolve(__dirname, "public/vendor/shoelace"),
        },
      ],
    }),