postinstall-build

npm install postinstall-build --save

What it does:

1. Check if your build artifacts exist
2. If not, temporarily install devDependencies and build
3. Clean up anything left behind... and that's it!

Usage

postinstall-build <PATH_TO_BUILD_ARTIFACT> <BUILD_COMMAND>

Explanation

Sometimes you want to install or depend on a package from someplace other than NPM – for example, from a git URL. If the package needs to be transpiled by a tool like Babel, then this can be tricky: most people put their build step in the version or prepublish hooks, and if you're not installing from NPM then this step probably wasn't run (unless the build artifacts are checked into source).

One solution is to add a check to the package's postinstall hook: if the build artifacts don't exist, then build! The annoying part is that this necessitates having your build dependencies (like Babel or webpack) available – in other words, they'd need to be production dependencies instead of devDependencies, even though the module itself doesn't require them (unlike real dependencies, they're only used in the build step). That means even everyone installing from NPM wastes time installing them, even though they already have the build artifacts!

This helper fixes that. Just tell it where a build artifact is and what your build step is, and it'll do the rest. Used as intended, postinstall-build should be a production dependency.

Here's an example using Babel:

{
  "scripts": {
    "build-lib": "babel -d lib src",
    "postinstall": "postinstall-build lib 'npm run build-lib'"
  },
  "dependencies": {
    "postinstall-build": "0.2.x"
  },
  "devDependencies": {
    "babel": "5.x.x"
  }
}

The postinstall-build helper will check whether the first argument, lib, exists. If not, it will run the second argument, npm run build-lib. Because build-lib requires Babel, a dev dependency, it will run npm install --only=dev before building. When the build is done, it will run npm prune --production to clean up. That's it!