[9.5.3] Next/_error.jsx style from modules.scss not working

[vdiazroa]

Bug report

Describe the bug

since 9.5.3 ( in 9.5.2 works fine), the custom error page has broken styles

To Reproduce

using sass to styling

create custom error page _error.jsx (tsx in my case)

need to build to see the actual error page, and try to create an error
(yarn build && yarn start)

in the error page the global style works fine
but every module.scss is broken even for the main error page or for imported components

System information

• sass: 1.26.10
• OS: [macOS catalina || ubuntu 18.04 lts]
• Version of Node.js: [v10.22.0 || v13.14.0]

[TasukuUno]

Hi, the same for me.
Here's example app to reproduce. I hope this helps you.

https://github.com/TasukuUno/repro-nextjs-16931

[JamieMason]

In trying to debug this locally I can see that none of the paths provided to getCssLinks contain paths to css files from css modules:

next.js/packages/next/pages/_document.tsx

Line 160 in b2d1d87

getCssLinks(files: DocumentFiles): JSX.Element[] | null {

Tracing back I can see this line in getDocumentFiles, which looks like it could be a good candidate for the cause of the problem:

next.js/packages/next/pages/_document.tsx

Line 59 in b2d1d87

pathname !== '/_error' ? getPageFiles(buildManifest, pathname) : []

but that line was changed 2 months ago in 9fcf39a. Tracing back further we reach getPageFiles, the last change there was 3597978 to "Modify low priority files in manifest", possibly whatever is going on in here could be the cause? The intent is hard to determine but these amends may have broken the contract for the data needed to get the CSS paths?

next.js/packages/next/next-server/server/render.tsx

Lines 685 to 701 in 3597978

	if (page in filteredBuildManifest.pages) {
	filteredBuildManifest = {
	...filteredBuildManifest,
	pages: {
	...filteredBuildManifest.pages,
	[page]: [
	...filteredBuildManifest.pages[page],
	...filteredBuildManifest.lowPriorityFiles.filter((f) =>
	f.includes('_buildManifest')
	),
	],
	},
	lowPriorityFiles: filteredBuildManifest.lowPriorityFiles.filter(
	(f) => !f.includes('_buildManifest')
	),
	}
	}

Link here to the diff where the above was introduced in commit 3597978

[JamieMason]

There is a workaround here: #16784 (comment)

[balazsorban44]

This issue has been automatically locked due to no recent activity. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.