Compatibility with yarn

[igorklopov]

yarn === npm install also yarn !== npm publish

[iarna]

Huh, I was under the impression that Yarn was using npm to run lifecycle scripts? Is that just for an npm run stand in?

[igorklopov]

Seems they don't use npm code, but they say "yay compatibility":
https://github.com/yarnpkg/yarn/blob/master/src/cli/commands/install.js#L869

[iarna]

Kind of, they don't support prepare or prepublishOnly, which are in npm today and were specced out from around the time they started work on yarn (maybe before). =p

[FezVrasta]

May you merge this please?

[igorklopov]

Please don't be demanding to yarn. We ask you to consider yarn as npm@3. Once yarn supports prepare and prepublishOnly i promise to make a new PR probing yarn version and deciding to turn on this discussed PR feature or not.

[iarna]

Ok, so the main delay here was that I wanted to verify that install was the only time Yarn would run prepublish. It is not.

Yarn has a publish command that runs the prepublish lifecycle:

See: lib/cli/commands/publish.js in the Yarn source.

Because of that, this PR is going to need revision to detect that usage.

[garthk]

Treating prepublish as equivalent to publish will also help lerna users using transpilers. My situation:

• lerna bootstrap runs npm prepublish in each package directory
• in-publish fails, so
• Transpiling doesn't happen, so
• dist/index.js doesn't exist, so
• Attempts to require the package fail

This private fork does the trick:

'use strict'
function inCommand (cmd) {
  try {
    var npm_config_argv = JSON.parse(process.env['npm_config_argv'])
  } catch (e) {
    return false
  }

  if (typeof npm_config_argv !== 'object') process.exit(1)
  if (!npm_config_argv.cooked) process.exit(1)
  if (!npm_config_argv.cooked instanceof Array) process.exit(1)

  var V
  if (npm_config_argv.cooked[0] === 'run') npm_config_argv.cooked.shift()
  while ((V = npm_config_argv.cooked.shift()) !== undefined) {
    if (/^-/.test(V)) continue
    if (cmd.test(V)) return true
    return false
  }
  return false
}

exports.inPublish = function () {
  return inCommand(/^(?:pre)?pu(b(l(i(sh?)?)?)?)?$/)
}

exports.inInstall = function () {
  return inCommand(/^(?:pre)?i(n(s(t(a(ll?)?)?)?)?)?$/)
}

I'd argue it's a breaking change, and would require a semver major bump.

[iarna]

@garthk It's not clear to me what you're trying to change? Can you PR that so I can see a diff?