Depending on module with postinstall script using gulp broken on npm 3

I’m developing a node app (let’s call it foo) that depends on another npm module (let’s call it bar) that has "postinstall": "gulp build" (to run babel over some es6 code). The bar module also has a devDependency on gulp to make sure people can install the module even if they don’t have gulp installed globally.

When I npm install in foo, the installation of the bar module fails with:

Local gulp not found in /path-to/foo/node_modules/bar
Try running: npm install gulp

This is an error message from gulp, not npm. In fact, gulp has some logic to check whether gulp is installed locally in the module depending on it (in this case, /path-to/foo/node_modules/bar/node_modules/gulp).

Since npm 3 installs all modules flat, the gulp module ends up underneath foo, not bar, causing the gulp cli to exit with this error.

Is there any way around this?

[bennycode]

I just came across the same issue… I published a node module which has the following entries in package.json:

"scripts": {
  "postinstall": "gulp build",
  "test": "gulp test"
}

Unfortunately people, who install my library, get an error during the postinstall step because gulp cannot be found. But I expected npm to find the local gulp which is declared in my library’s development dependencies:

"devDependencies": {  
  "gulp": "^3.9.1",
  ...
}

Do I need to declare gulp as usual dependency to use gulp build in a postinstall task?

[BrunoZell]

As of npm@5 the script prepublish is deprecated. You can use prepare instead. Make sure to add gulp-cli to your devDependencies so that it is not required as a global module.