Creates a decoupled optimizer that can build new platform plugins so that they can be distributed as static assets, created at build time, loaded independently in the browser, and never rebuilt in the distributable. See the @kbn/optimizer readme for some more details on the new optimizer.

styles

.scss files can now be imported directly from JS/TS module. node-sass is used to build the linked file as if it was built using node-sass directly (using node-sass module resolution, not webpack's). An import for the src/legacy/ui/public/styles/_styling_constants.scss file is automatically injected at the beginning of each .scss file imported by a JS/TS module so that users can access the styling constants without explicitly pulling in the styles (as requested by design). The styles required by a module are a part of the JS bundle (both light and dark mode variants) and are injected into the page when the module is loaded based on the theme selected for the current page. Light/dark mode variants are built the same way they used to be, by replacing eui_colors_light with eui_colors_dark when it's found in any imported path. A page reload is still required to switch themes.

changes made to plugins

• new platform plugins now import their root scss files rather that defining uiExports.styleSheetPaths (ie src/plugins/expressions/public/index.ts)
• any legacy plugins that were purely for building styles have been removed

performance

A primary performance goal of the new optimizer is to build everything as quickly as possible, it does this by running webpack compilers in parallel. This can cause the CPU usage to spike for a bit while the initial build completes. Most people I've talked to prefer that to longer build times, but if you prefer not pegging your CPU you can lower the maximum number of workers using the KBN_OPTIMIZER_MAX_WORKERS environment variable. Setting it to 1 will make the new build take a while, but will cause the least amount of load on your system.

caching

When the files in a bundle haven't changed since the last time it was built, the webpack compiler for that bundle will not be started and instead a watcher will be created to watch the files for changes. Checkout the caching section of the readme

Dev Docs

Plugins that have been migrated to the "new platform" are built with a new system into their own target/public directory. To build third-party plugin's with this new system either pass --plugin-path to node scripts/build_new_platform_plugins or use the @kbn/optimizer package in the Kibana repo to build your plugin as described in the readme for that package.