reject the request promise when reading a response body fails - #376

Overview

If the connection breaks off after the response headers, reading the body fails. nano 11 currently swallows that failure. JSON responses resolve with ''. For text, multipart and binary responses, the error escapes the un-awaited responseHandler, so the request promise never settles and Node reports an unhandled rejection. See #375 for details and a reproduction.

This PR makes two changes to lib/nano.js:

• JSON bodies: read with response.text(), then JSON.parse(). Only the parse step is inside the try/catch. A complete body that isn't valid JSON still resolves '' as before, and a failed read now propagates. This keeps the "ignore unparseable bodies" behaviour without inspecting error types (SyntaxError vs TypeError).
• relax(): the .then() callback now returns the responseHandler(…) promise, so the existing .catch() handles any failure from it. A body-read failure then rejects the same way a connection failure before the headers already does: error happened in your connection. Reason: SocketError: other side closed. The promise can't settle twice: responseHandler calls resolve as its last step, after every await. The error path (responseHandler(e, …) with a non-Response) only calls reject.

Unchanged, on purpose:

• Non-2xx responses: if reading the error body fails, the existing catch sets the body to '' and the request still rejects with the HTTP status code. The caller already gets a rejection with the most useful information, so I left that branch alone.
• Streaming requests (opts.stream): these go through streamResponseHandler and pipe the body into the returned stream. That path doesn't have this problem.

Testing recommendations

npm test passes: 238 tests, including 4 new ones in test/nano.responsebody.test.js:

• JSON body breaks off → rejects (previously resolved '')
• text/plain body breaks off → rejects (previously never settled; unhandled rejection)
• application/octet-stream body breaks off → rejects (same as above)
• complete application/json body that isn't valid JSON → still resolves ''

Without the change to lib/nano.js, the first three fail and the fourth passes.

The new tests use a real http.createServer on 127.0.0.1 (random port) instead of undici's MockAgent. MockAgent always delivers the full reply body and then completes, so it can't simulate a connection that drops partway through the body. The server promises content-length: 100, writes part of the body, then destroys the socket. undici then raises the same TypeError: terminated (cause SocketError: other side closed) as it does against a real CouchDB. The file doesn't load test/mock.js, and node --test runs each file in its own process, so the other tests' global MockAgent (which has disableNetConnect()) doesn't apply here.

Also checked:

• The new tests pass on Node 20.20.2 (the engines minimum) and Node 24.21.0.
• standard reports no errors in the new test file and no new errors in lib/nano.js.
• node --test --experimental-test-coverage covers all changed lines.

GitHub issue number

Fixes #375

Related Pull Requests

None.

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes; (no documentation changes needed: this restores the documented promise semantics)

This PR was prepared with the help of Claude Code (an AI coding assistant) and reviewed by me before submission. The commit carries a Co-Authored-By trailer, as recommended by the ASF generative tooling guidance.

🤖 Generated with Claude Code