When using the latest sass-loader (right now it is 8.0.0) with the latest preact-cli (3.0.0-next.19), preact build fails with an error:
Module build failed (from /usr/lib/node_modules/preact-cli/node_modules/mini-css-extract-plugin/dist/loader.js):
ModuleBuildError: Module build failed (from /usr/lib/node_modules/preact-cli/lib/lib/webpack/proxy-loader.js):
ValidationError: Invalid options object. Sass Loader has been initialised using an options object that does not match the API schema.
- options has an unknown property 'includePaths'. These properties are valid:
object { implementation?, sassOptions?, prependData?, sourceMap?, webpackImporter? }
This happens because includePaths was moved to sassOptions. However, the issue is not yet fixed in preact-cli.
One of the possible solutions — use sass-loader 7.3.1.
preact-cli 3 and sass-loader 8