Run a project's local tools

Run the tools a project installed in node_modules/.bin by name, from any directory inside it, with runPath — npm-run-path's contract, without the dependency.

npm run puts every node_modules/.bin from the working directory up in front of PATH, which is why a script can say lint rather than ./node_modules/.bin/lint. runPath() builds the same PATH, so a program can run a project's tools the way its scripts do:

local.mjs

import { chmodSync, mkdirSync, writeFileSync } from 'node:fs';
import { relative } from 'node:path';

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

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

// A project with a locally installed tool, and a script one directory down.
mkdirSync('node_modules/.bin', { recursive: true });
writeFileSync('node_modules/.bin/lint', "#!/usr/bin/env node\nconsole.log('lint: 0 problems');\n");
chmodSync('node_modules/.bin/lint', 0o755);
mkdirSync('packages/app', { recursive: true });

const base = runtimeWith();
const runtime = { ...base, cwd: `${base.cwd}/packages/app` };
const local = { ...runtime, env: { ...runtime.env, PATH: runPath({ runtime }) } };

const result = await run('lint', [], { runtime: local });
console.log(result.stdout.trim());
console.log('from', relative(base.cwd, result.executable.from));

node local.mjs

lint: 0 problems
from node_modules/.bin

The walk starts at the runtime's working directory, goes up one directory at a time, and stops at the filesystem root — or the drive root on Windows, where the walk is in Windows dialect. The nearest node_modules/.bin comes first, so a workspace package's own install wins over the root's. which.test.ts checks all three.