rolldown/rolldown

Three concrete flows were followed through their implementations: CLI config bundling, programmatic output generation/writing, and watch initialization/rebuild. The traces preserve meaningful branches such as native versus bundled config loading and generate versus write. Cleanup and recovery are part of the observed behavior, including worker/runtime release and watch registration after failed scans.

• CLI startup: bin/cli.mjs imports dist/cli.mjs → CLI checks Node compatibility → main calls parseCliArguments → applies environment assignments → selects help, version, config bundling, positional bundling, or help fallback.
  packages/rolldown/bin/cli.mjs#L1-11packages/rolldown/src/cli/index.ts#L9-54
• Config flow: bundleWithConfig sets watch environment flags when needed → loadConfig discovers/selects the loader → bundled TS configs pass through bundleTsConfig and dynamic import with unlink cleanup; native loading uses freshImport or a timestamped import.
  packages/rolldown/src/cli/commands/bundle.ts#L15-29packages/rolldown/src/utils/load-config.ts#L77-84packages/rolldown/src/utils/load-config.ts#L143-185
• Config output flow: resolve the config function with rawArgs → bundleInner iterates configs → rolldown merges CLI input overrides → sequential build.write calls merge output overrides → finally build.close → output-size reporting.
  packages/rolldown/src/cli/commands/bundle.ts#L25-42packages/rolldown/src/cli/commands/bundle.ts#L152-186
• Programmatic flow: rolldown validates input and calls options hooks → constructs RolldownBuild/startAsyncRuntime → generate/write invokes #build → createBundlerOptions → BindingBundler.generate/write → ClassicBundler.create_bundle.
  packages/rolldown/src/api/rolldown/index.ts#L39-42packages/rolldown/src/api/rolldown/rolldown-build.ts#L29-34packages/rolldown/src/api/rolldown/rolldown-build.ts#L124-142crates/rolldown_binding/src/binding_bundler.rs#L39-66
• Core output flow: Bundle.generate/write → scan_modules → ScanStage.scan/build_start/fetch_modules → build_end → bundle_up → LinkStage.link → GenerateStage.generate → additional files/generate_bundle → filename validation; write additionally performs filesystem writes/write_bundle.
  crates/rolldown/src/bundle/bundle.rs#L45-79crates/rolldown/src/stages/scan_stage.rs#L182-205crates/rolldown/src/bundle/bundle.rs#L139-147crates/rolldown/src/bundle/bundle.rs#L274-338
• Build cleanup: RolldownBuild.close claims runtime release before awaiting → stops workers → awaits BindingBundler.close → releases the runtime in finally; asyncDispose delegates to close.
  packages/rolldown/src/api/rolldown/rolldown-build.ts#L92-110crates/rolldown_binding/src/binding_bundler.rs#L181-195
• Watch startup: watch returns WatcherEmitter while createWatcher asynchronously runs per-output options hooks/createBundlerOptions → constructs BindingWatcher → starts the runtime → schedules run on nextTick → coordinator emits START and builds each task.
  packages/rolldown/src/api/watch/index.ts#L37-40packages/rolldown/src/api/watch/watcher.ts#L69-88packages/rolldown/src/api/watch/watcher.ts#L111-136crates/rolldown_watcher/src/watch_coordinator.rs#L108-142
• Watch rebuild: file messages enter debounce processing → run_build_sequence dispatches changes/watchChange/restart/START → affected tasks build; WatchTask clears resolution/tsconfig caches, scans, registers watches before checking scan errors, and selects bundle_generate when skipWrite is set.
  crates/rolldown_watcher/src/watch_coordinator.rs#L57-99crates/rolldown_watcher/src/watch_coordinator.rs#L145-180crates/rolldown_watcher/src/watch_task.rs#L87-125