replayio/nextjs-inaccurate-sourcemaps

A next.js app for reproducing an issue with sourcemaps

This is a Next.js project bootstrapped with create-next-app to show an issue with next.js sourcemaps.

STR:

• npm run build
• upload .next/static/chunks/main-26f0defd1fe4aedb.js[.map] to https://evanw.github.io/source-map-visualization/
• select webpack://_N_E/node_modules/@swc/helpers/esm/_interop_require_wildcard.js as the original source
• for comparison, upload .next/static/chunks/pages/_app-27374a655d3a2ebe.js[.map] to https://evanw.github.io/source-map-visualization/ and select webpack://_N_E/src/_interop_require_wildcard.js

Alternatively, you can look at these sourcemaps here:

• webpack://_N_E/node_modules/@swc/helpers/esm/_interop_require_wildcard.js: https://app.replay.io/recording/5072126e-507f-43d9-8c9e-889ad2bfd0dd/sourcemap/o4-80-c194bb-ec5646
• webpack://_N_E/src/_interop_require_wildcard.js: https://app.replay.io/recording/5072126e-507f-43d9-8c9e-889ad2bfd0dd/sourcemap/o6-6-c194bb-5d30d7

The sourcemap viewer shows that in the first sourcemap (of a source under node_modules) almost all sourcemap entries point to the first column of a line in the original source. This makes it impossible to do "scope mapping" (showing scopes with original variable names) in a debugger.