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expo start crashes when an API route calls console.log (Node < 22.14, Metro index source maps) #50803
Description
Summary
With web.output: "server", any console.log in an API route kills expo start on the first request that reaches it, on Node before v22.14.0:
TypeError: The "payload" argument must be of type object. Received null
at cloneSourceMapV3 (node:internal/source_map/source_map:365:3)
at new SourceMap (node:internal/source_map/source_map:145:21)
at Object.findSourceMap (node:internal/source_map/source_map_cache:348:17)
at wrapCallSite (.../@expo/require-utils/build/stacktrace.js:138:30)
at Error.prepareStackTrace (.../@expo/require-utils/build/stacktrace.js:103:38)
at prepareStackTraceCallback (node:internal/errors:144:29)
at getErrorMessage (.../finalhandler/index.js:176:15)
On newer Node it doesn't crash, but stack traces from API routes and server rendering point into the evaluated bundle instead of the original source.
Cause
@expo/require-utils gives Node the server bundle's source map through a sourceMappingURL file. Since Metro 0.87 (#50135), that map is an index map (sections, no top-level sources), which Node can't load from a file. Node caches an entry with a null payload for the module.
- Before lib: suppress source map lookup exceptions nodejs/node#56299 (v22.14.0, v23.6.0),
module.findSourceMapthrows for such a module instead of returningundefined. Theconsole.logoverride inserverLogLikeMetrocaptures a stack, soprepareStackTracethrows from inside the route handler. The error handler then formats that error's stack, which throws again, uncaught. - On any Node version, the bundle has no usable source map, so frames are left unmapped.
Repro
SDK 58 (expo@58.0.0-preview.7, expo-router@58.0.8), Node v22.13.1:
- Set
web.outputto"server". - Add
app/api/log+api.ts:export function GET() { console.log('hello'); return Response.json({}); }
- Run
npx expo startand request/api/log. The process exits with the error above.
Fix
Two changes, on branch robhogan/cli-flatten-eval-source-map, PRs to follow:
@expo/require-utils: treat a throwingfindSourceMaplike a missing map and fall back to the unmapped frame.@expo/cli: flatten the map withflattenSourceMapbeforeevalModule, as the export path inMetroBundlerDevServeralready does, so Node gets a map it can load and frames map to source again.
Activity
expo-bot commentedon Sep 29, 2026
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