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Tobias Koppers
d42ea11842
### What? Make the production test harness wait for a build process's piped stdio to close before `NextStartInstance.start()` continues to launch the server or reports a build failure. ### Why? A child process's `exit` event can fire before trailing stdout and stderr have been delivered to the parent. This can make start-mode tests intermittently miss diagnostics emitted near the end of a production build, even though the build itself reported them correctly. The standalone `build()` helper already uses the later `close` lifecycle event to avoid this race. Applying the same rule to the build phase inside `start()` removes the equivalent latent output-drain hazard and makes child-process handling consistent across the harness. ### How? Resolve the build phase on the child process's `close` event. Unlike `exit`, `close` is emitted after piped stdio closes, so all trailing build output has reached the harness before it starts the server or rejects the build. Exit-code and signal handling remain unchanged. ### Verification - `pnpm types` - `pnpm test-start-webpack test/production/production-build-dir/production-build-dir.test.ts` - `pnpm test-start-webpack test/production/app-dir/sync-io-blocks-root/sync-io-blocks-root.test.ts` - Repeated webpack stress campaign for the sync-IO suite: 5/5 runs, including 20/20 `--debug-prerender` route cases - Prettier and ESLint on `test/lib/next-modes/next-start.ts` <!-- NEXT_JS_LLM --> <!-- fleet 821362ed-9f96-4e53-b56e-49bf00e878b9 --> Co-authored-by: vercel-fleet-prod[bot] <318278635+vercel-fleet-prod[bot]@users.noreply.github.com> Co-authored-by: Tobias Koppers <1365881+sokra@users.noreply.github.com>