[kilisamemarisaaa]

Summary

• ignore epilogue chunks that arrive after Dicer has recognized the closing multipart boundary
• complete the outer write callback instead of waiting forever for a drain from a finished parser
• add a Busboy-level regression test for an epilogue delivered in a later event-loop turn

Fixes #228.

Root cause

After the closing boundary, Dicer marks itself finished and resets its internal boundary parser. Once pending parts have ended, the multipart wrapper also ends Dicer. A later Busboy write still called parser.write() on that completed Dicer. The call returned false, so Multipart stored the outer callback while waiting for a drain event that can never occur. As a result, Busboy.end() stayed queued and finish was never emitted.

The write path now ignores bytes only when Dicer's closing-boundary state is set. Other non-writable states, such as a parser destroyed before the closing boundary, are not mistaken for epilogue. The regression test also verifies field -> epilogue write callback -> finish ordering and a single finish event.

Reproduction

On unmodified main (4e8de12), a complete body followed by epilogue in the same chunk emitted field=value and finish. Writing that same epilogue after setImmediate emitted the field but still had finish=false and no error after 200 ms.

Validation

• npm test: 237 unit tests passed with 100% statement, branch, function, and line coverage; 101 type assertions passed
• npm run lint
• node --test test/types-multipart-coverage.test.js: 9 passed
• Windows 11, Node.js 24.12.0