feat: log compile stats

[dominikg]

We want to set prebundleSvelteLibraries: true by default and this has implications for users.

Esp. with large component libraries it can lead to significant delays when loading the dev page in the browser or building.
To make these transparent, we collect compile time statistics and log them.

example output for dev:

  ➜  Local:   http://localhost:5173/
  ➜  Network: use --host to expose
5:43:05 PM [vite-plugin-svelte] prebundle libraries in progress ...
5:43:19 PM [vite-plugin-svelte] ssr compile in progress ...
5:43:24 PM [vite-plugin-svelte] prebundle libraries done.
package                         files     time     avg
carbon-icons-svelte              2002   10.02s   5.0ms
carbon-components-svelte          206    2.42s  11.7ms
5:43:28 PM [vite-plugin-svelte] ssr compile done.
package                                 files    time     avg
carbon-icons-svelte                      2002   2.68s   1.3ms
carbon-components-svelte                  206   0.53s   2.6ms
playground-big-component-library-kit        3   9.0ms   3.0ms

example output for build:

> vite build

vite v3.2.3 building for production...
✓ 2333 modules transformed.
5:44:47 PM [vite-plugin-svelte] dom compile done.
package                                 files     time     avg
carbon-icons-svelte                      2002    9.02s   4.5ms
carbon-components-svelte                  206    2.27s  11.0ms
playground-big-component-library-kit        4   84.6ms  21.1ms
@sveltejs/kit                               1   22.0ms  22.0ms
vite v3.2.3 building SSR bundle for production...
✓ 2351 modules transformed.
5:44:55 PM [vite-plugin-svelte] ssr compile done.
package                                 files    time     avg
carbon-icons-svelte                      2002   2.96s   1.5ms
carbon-components-svelte                  206   0.59s   2.9ms
playground-big-component-library-kit        4   8.6ms   2.1ms
@sveltejs/kit                               1   1.9ms   1.9ms

These stats are logged at the info level.

You can disable them via the new experimental.disableCompileStats option for vite-plugin-svelte

// svelte.config.js
export default {
  vitePlugin: {
    experimental: {
      disableCompileStats: true, // true disables completely, 'dev' for dev and 'build' for build
    }
  }
}

[dominikg]

added an option to disable because --logLevel warn doesn't seem to propagate to the second vite build kit kicks off and it also removes other useful logging.

[bluwy]

Moving the option to experimental sounds fine to me 👍 I hope we can start reducing the options for v2 though so there's less to document and nicer ootb experience.