Loading Sourcemaps for own Library in Webpack 4

I have a library MyLibrary that is loaded inside MyApp. Ever since upgrading to webpack 4, sourcemaps no longer get loaded by the app to debug into the library and only the webpack compiled code is shown. Sourcemaps for each the library and the app itself work fine.

A minimum reproducible repo can be found here: https://github.com/sqwk/webpack-library-test

Also see this Stackoverflow question about the topic: https://stackoverflow.com/questions/50910220/webpack-4-load-library-sourcemap/51253629#

Is this a configuration error or is there a known incompatibility with webpack 4?

[mfedderly]

I think that this depends on the devtool setting of the final webpack step. cheap-eval-source-map doesn’t give me the sourcemaps I’m looking for but eval-source-map does. I suspect you need the “original source” devtools options.

[alexander-akait]

When you build library for publishing you should use devtool: 'source-map' value if you want provide source maps for other developers (source-map-loader automatically loads them). Sorry it’s out of our control. In most tools for building library it is described https://webpack.js.org/configuration/devtool/#production. Anyway if you want to send a PR with docs here feel free to do it.