[maxymlyskov]

Description

Legacy-mode callbacks are wired as promise.then(reply => callback(null, reply)).catch(err => callback(err)), so when the callback throws on success, the .catch calls it again with its own error. That's in all four places that call back: the generated commands (#createCommand), sendCommand, quit and multi().exec.

With a callback that throws, against Redis 8.10.2, on master:

set: callback ran 2 times: reply="OK" | err=bug in set callback
sendCommand: callback ran 2 times: reply="v" | err=bug in sendCommand callback
exec: callback ran 2 times: reply=["v"] | err=bug in exec callback

With this change each one runs once.

The reply transform (TRANSFORM_LEGACY_REPLY, and transformReplies for exec) now runs in its own .then, and the callback is called from .then(reply => callback(null, reply), err => callback(err)), so a transform error like the MultiErrorReply from exec still reaches the callback. A throw from the callback now ends as an unhandled rejection, same as master after the second call.

Added a test per call site in legacy-mode.spec.ts; all 4 fail on master. npm run build && npm test passes and lint is clean, apart from the sentinel destroy() from an end listener tears down a reentrant reopen case, which failed once in the full run here and passes 5 out of 5 when run alone.

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Checklist

• Does npm test pass with this change (including linting)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

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Note

Medium Risk
Touches promise/callback wiring on all legacy API entry points; behavior change for throwing callbacks (no second err callback) but aligns with expected Node semantics and is well covered by new tests.

Overview
Fixes double invocation of legacy-mode Node callbacks when the user callback throws after a successful Redis reply.

Previously, success handlers ran inside .then(...) with a following .catch(err => callback(err)), so a throw from callback(null, reply) was treated as a rejection and triggered a second call with that error. sendCommand, generated commands (e.g. set), quit, and multi().exec all used this pattern.

The implementation now invokes the callback from a single .then(onFulfilled, onRejected) so throws from the callback propagate as unhandled rejections instead of a second callback. Where TRANSFORM_LEGACY_REPLY or transformReplies applies, the transform runs in a separate .then first so transform/exec errors still reach the callback once.

Regression coverage adds a shared callsOfThrowingCallback helper and one test per call site, asserting exactly one [null, reply] and that the thrown error surfaces as unhandled.

^{Reviewed by Cursor Bugbot for commit c1c7b2c. Bugbot is set up for automated code reviews on this repo. Configure here.}

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	⚠️ Failed 2026-10-27T15:36:50.568954Z We couldn’t complete this review. Comment @codex review to try again.	c1c7b2c	PR opened

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[nkaradzhov]

Thanks, LGTM.