Summary

inquirerer/src/commander.ts defined defaultCLIOptions with two eager properties:

input: process.stdin,
output: process.stdout,

process.stdin / process.stdout are Node getters that lazy-construct the underlying Readable / Writable on first access. When fd 0 is a pipe (Jest workers, spawned children, any backgrounded process — i.e. the common case for anything running under jest), constructing stdin registers a libuv PIPEWRAP handle that the runtime must close before exit.

Because those properties were evaluated at module-load time, any library that transitively required inquirerer without ever constructing a CLI still opened stdin as a pure import side-effect. The chain that actually burned us:

pgsql-test/index.js:18     →  require("./admin")
pgsql-client/admin.js:4    →  require("@pgpmjs/core")
@pgpmjs/core/index.js:18   →  require("./core/class/pgpm")
template-scaffold.js:11    →  require("genomic")
genomic/index.js:19        →  require("inquirerer")
inquirerer/commander.js:14 →  input: process.stdin   ← leak

That surfaced in peptide-app-demo#40 as a PIPEWRAP open-handle warning from jest --detectOpenHandles even though no test was doing anything CLI-related.

Fix

Convert input and output into accessor properties (getters) so process.stdin / process.stdout are only touched when someone actually reads them (i.e. when new CLI(...) runs through commander.ts:43-46). Behaviour is unchanged for direct consumers — defaultCLIOptions.input still returns process.stdin on read.

export const defaultCLIOptions: CLIOptions = {
  version: `inquirerer@${getVersion()}`,
  noTty: false,
  get input()  { return process.stdin;  },
  get output() { return process.stdout; },
  minimistOpts: { alias: { v: 'version' } },
};

Repro before / after

Probe: require('inquirerer'), then in setImmediate dump process._getActiveHandles() grouped by constructor name. Stdin piped (echo '' | node probe.js) so fd 0 is PIPEWRAP, matching a Jest worker.

Regression test

Added <ref_file file="/home/ubuntu/repos/dev-utils/packages/inquirerer/tests/no-eager-stdio.test.ts" /> — three assertions:

1. Object.getOwnPropertyDescriptor(defaultCLIOptions, 'input'|'output') is a getter, not a data property (structural guard — cheapest).
2. Reading the getters still returns process.stdin / process.stdout (no behaviour regression).
3. Spawns a fresh node with piped stdin, requires the built dist/index.js, and asserts _getActiveHandles() contains no Socket/WriteStream entries (end-to-end guard that survives future refactors).

All 9 suites / 153 tests pass locally on constructive-io/dev-utils main.

Review & Testing Checklist for Human

• Sanity-check the getter conversion in <ref_snippet file="/home/ubuntu/repos/dev-utils/packages/inquirerer/src/commander.ts" lines="19-39" /> — I preserved the CLIOptions interface shape (plain Readable/Writable) because TS treats getters as equivalent to data properties for structural typing; make sure nothing in your downstream consumers assumes Object.keys(defaultCLIOptions) enumerates input/output as own-data properties. (Getters are still own and enumerable, so Object.keys/{...defaultCLIOptions} both continue to include them — but worth a glance.)
• Verify the end-to-end regression test in <ref_file file="/home/ubuntu/repos/dev-utils/packages/inquirerer/tests/no-eager-stdio.test.ts" /> isn't flaky on slower CI — it spawns a child node process. Timed at ~150ms locally.
• Confirm you'd like a patch release (4.7.1) cut from this so peptide-app-demo → pgsql-test picks up the fix without waiting for a minor bump.

Notes

• No behaviour change for any consumer that reads defaultCLIOptions.input / .output — they still return process.stdin / process.stdout verbatim.
• The CLI constructor destructures these at call-time (<ref_snippet file="/home/ubuntu/repos/dev-utils/packages/inquirerer/src/commander.ts" lines="51-58" />), so the only observable difference is when stdin is opened: at new CLI() rather than at import 'inquirerer'.
• Once this merges + publishes, the --detectOpenHandles warning in peptide-app-demo/packages/integration-tests disappears with no change in that repo; the Jest scripts can keep --detectOpenHandles on as a guard against new leaks without false positives from this chain.
• I also cherry-picked the same fix into pyramation/inquirerer (the 2.x homepage) locally — happy to open a PR there too if you want the public-mirror repo to stay in sync, but I didn't have push access so it's currently just a local branch.

Link to Devin session: https://app.devin.ai/sessions/81001448b7c54b8099437f706d44a30d
Requested by: @pyramation