Check node and yarn

[gauravtiwari]

Related to #217

@dhh Is this good enough?

[matthewd]

I don't think we need to be chatty on the happy path.

Is this the first time we're relying on a node executable to be on the path?

[gauravtiwari]

@matthewd Right, yeah a bit chatty 😄 Yeah, I think so. We have a yarn task in Rails 5.1 - https://github.com/rails/rails/blob/8e9e94391902b854662ba5eb06cc006cc4e85212/railties/lib/rails/generators/rails/app/templates/bin/yarn, but no node check anywhere else.

[ytbryan]

Thanks for this PR @gauravtiwari .

My suggestion. Use Node since all instructions mention Node instead of Node.js for consistency

 puts "Node is not installed"
 puts "Please install node at https://nodejs.org/en/download/ and run bundle exec rails webpacker:install"
 exit!

[ytbryan]

Requires with a s

Node with a N

[ytbryan]

My suggestion:

 puts "Webpacker requires Node 6.4.0+ and you are using #{node_version}"
 puts "Please upgrade Node at https://nodejs.org/en/download/ and run bundle exec rails webpacker:install"
exit!

[ytbryan]

Node with a N, please

[gauravtiwari]

Thanks for reviewing 😄 Pushed some updates, it's less chatty now and uses Node.js to make it more uniform. Apparently, that's how it is everywhere.

[rmosolgo]

👍 thanks @gauravtiwari ! I thought that the installation was successful, but turns out I didn't have Yarn yet:

         run  ./bin/yarn add webpack webpack-merge js-yaml path-complete-extname webpack-manifest-plugin babel-loader coffee-loader coffee-script babel-core babel-preset-env compression-webpack-plugin rails-erb-loader glob extract-text-webpack-plugin node-sass file-loader sass-loader css-loader style-loader postcss-loader autoprefixer postcss-smart-import precss from "."
Yarn executable was not detected in the system.
Download Yarn at https://yarnpkg.com/en/docs/install
Installing dev server for live reloading
         run  ./bin/yarn add --dev webpack-dev-server from "."
Yarn executable was not detected in the system.
Download Yarn at https://yarnpkg.com/en/docs/install
Webpacker successfully installed 🎉 🍰