Which binary ran?

Diagnose a build that differs between machines: list every install of a tool on PATH, best first, and report which one a run actually used.

Two machines, one command, two answers — and usually two installs of the same tool on one of them. The fastest way to the finding is to ask for every match, and for the PATH entry each came from:

doctor.mjs

import { relative } from 'node:path';

import { run } from 'bellpull';
import { whichAllSync } from 'bellpull/which';

import { install, runtimeWith } from './tools.mjs';

install();
const runtime = runtimeWith('bin', 'vendor/bin');
const here = (p) => relative(runtime.cwd, p);

const hits = whichAllSync('greet', { runtime });
if (hits.length > 1) console.log(`${hits.length} installs of greet on PATH:`);
for (const [i, hit] of hits.entries()) console.log(`  ${i === 0 ? '→' : ' '} ${here(hit.path)}  (PATH entry ${here(hit.from)})`);

const result = await run('greet', [], { runtime });
console.log(`ran ${here(result.executable.path)}: ${result.stdout.trim()}`);

node doctor.mjs

2 installs of greet on PATH:
  → bin/greet  (PATH entry bin)
    vendor/bin/greet  (PATH entry vendor/bin)
ran bin/greet: hello from bin

Put this behind a doctor subcommand and a bug report carries the answer instead of a request for echo $PATH. The run result's executable is the one that actually ran, because bellpull spawns the file it resolved rather than handing the name back to be resolved again.