feat(dns): added support for a custom lookup function; (#5339)

[MitchLewis930]

PR_026

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Note

Medium Risk
Touches the core Node HTTP adapter request option wiring (DNS resolution path), which could affect connectivity/redirect behavior, but is scoped and covered by new unit/typing tests.

Overview
Adds Node-only request config support for DNS control by passing family and a custom lookup function through to the underlying Node http(s).request options.

Async lookup functions are now accepted by wrapping them into callback style via a new callbackify helper, and typings + tests were updated to cover both callback and async lookup variants (including async returning just an IP string).

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Cursor Bugbot has reviewed your changes and found 2 potential issues.

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TypeScript async lookup test missing async keyword

Medium Severity

The "lookup async" TypeScript test is missing the async keyword. The function returns a plain array ['127.0.0.1', 4] instead of a Promise as required by the type definition Promise<[address: string, family: number] | string>. This causes a type mismatch and doesn't correctly validate the async lookup type signature. The runtime test at test/unit/adapters/http.js:2151 correctly uses async.

 

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Promise-returning lookup functions not detected unless using async

Low Severity

The type definition allows any function returning Promise<[address, family] | string>, but the implementation only detects functions declared with the async keyword via utils.isAsyncFn(). A regular function that returns a Promise (e.g., function lookup(h, o) { return Promise.resolve(['127.0.0.1', 4]); }) won't be wrapped by callbackify, causing the HTTP request to hang since the callback is never invoked.

Additional Locations (1)

• index.d.ts#L347-L349