Go to webpack/lib/ModuleWarning and put console.log(this.name, this.warning, this.details) here https://github.com/webpack/webpack/blob/master/lib/ModuleWarning.js#L40

For anyone else facing the issue. Webpack doesn’t show any warning except the warning about serialization while caching because actual warning happens in child compilers used by mini-css-extract-plugin. And you need to specify { children: true } in webpack config to see the actual message. But it will show a lot of successful message with info about children.

Another option is to set experimentalUseImportModule flag for mini-css-extract-plugin in order to not use child compilers.

@alexander-akait Example in the initial post in this issue: webpack shows this ...<file with warning>... : No serializer registered for Warning with no actual warning text

and after your suggestion to add console.log

Go to webpack/lib/ModuleWarning and put console.log(this.name, this.warning, this.details) here https://github.com/webpack/webpack/blob/master/lib/ModuleWarning.js#L40

The string (45:3) Replace fill-available to stretch, because spec had been changed] will be shown.

stats option is set to minimal in my webpack config

@meskill You have warning in your CSS from autoprefixer, so we can’t cache this module due warning, you need fix warning

I totally understand that, my question was only about webpack output - currently it strips important information which will help to fix warnings

Maybe autoprefixer don’t provide more information, but we can provide this and print file where warning happens. Can you provide small example? Here place to improve https://github.com/webpack-contrib/postcss-loader/blob/master/src/Warning.js

This reply earlier in the thread helped me troubleshoot my silent CSS failure (I had one rule with an empty url that couldn’t resolve): https://github.com/webpack/webpack/issues/12458#issuecomment-763713922

How can we make this a more user-friendly message to explicitly log warnings?

Are these merely getting suppressed by autoprefixer?

It seems like that line of code is our needed serializer right there that should come included

@sokra @alexander-akait Can webpack show more detailed output for warnings like this?

Compare, warning showed by webpack: 2021-01-20-07:34:23 3|admin-webpack | <w> [webpack.cache.PackFileCacheStrategy] Skipped not serializable cache item 'mini-css-extract-plugin /home/admin/code/experimental/node_modules/css-loader/dist/cjs.js??ruleSet[1].rules[1].use[1]!/home/admin/code/experimental/node_modules/postcss-loader/src/index.js??ruleSet[1].rules[1].use[2]!/home/admin/code/experimental/node_modules/less-loader/dist/cjs.js??ruleSet[1].rules[1].use[3]!/home/admin/code/experimental/modules/browser/navigation/private/published_doc_interactions.less|0|Compilation/modules|/home/admin/code/experimental/node_modules/css-loader/dist/cjs.js??ruleSet[1].rules[1].use[1]!/home/admin/code/experimental/node_modules/postcss-loader/src/index.js??ruleSet[1].rules[1].use[2]!/home/admin/code/experimental/node_modules/less-loader/dist/cjs.js??ruleSet[1].rules[1].use[3]!/home/admin/code/experimental/modules/browser/navigation/private/published_doc_interactions.less': No serializer registered for Warning

And an actual warning from autoprefixer:

2021-01-20-07:48:38 3|admin-webpack   | ModuleWarning [Warning: Warning
2021-01-20-07:48:38 3|admin-webpack   | (45:3) Replace fill-available to stretch, because spec had been changed]

There is no way to figure out why the warning has appeared in the first place without console.log inside webpack/lib