[Feature idea] Execute current package's binary

[ehmicky]

When execa is used in unit tests to test the current package's CLI, it might look like this:

const PATH_TO_BINARY = `${__dirname}/../../bin/index.js`

test('should work', async t => {
  const output = await execa(PATH_TO_BINARY, ['arguments'])
  t.is(output, 'expected value')
})

To improve this use case, should we allow the following?

test('should work', async t => {
  const output = await execa('binary-name', ['arguments'])
  t.is(output, 'expected value')
})

It could be implemented like this:

• use readPkgUp[.sync](). This could be cached.
• get the bin field string or object
• if the name matches the file passed to execa, use the binary path instead

This would be behind a currentPackage: boolean option. We could default it either to false or true.

Advantages:

• it tests that the bin field in package.json is valid. This is something that is basically never checked in unit tests, but should.
• it decouples the binary path from the tests, which allows moving the file without rewriting the tests.

Is this a good idea?

[revelt]

I tested the readPkgUp, bin is indeed recognised. Idea looks good!

[sindresorhus]

I feel like this is outside the scope of execa. I've been wanting to make child process assertion library to make it easier to assert certain stuff from child processes, especially for interactive processes. Would be cool to have child process mocking built-in too. I imagine your idea would fit better in such library. I have no time to make it though, so feel free to go with it if you have time.

[ehmicky]

If it's as a separate library, I would imagine it to be restricted to this use case as:

const binPath = await getBinPath('binary-name')

Like this it could be used outside of execa as well. And for execa it would be:

import getBinPath from 'get-bin-path'

test('should work', async t => {
  const binPath = await getBinPath('binary-name')
  const output = await execa(binPath, ['arguments'])
  t.is(output, 'expected value')
})

What do you think? I could build that.

The only other package that does that seems to be resolve-bin but without promises, and not maintained it seems.

[sindresorhus]

👍 We could link to it from the readme.

[ehmicky]

Done by #339