Rails Precompile Failure With Bower Packages

I work with a team where we use bower packages in the vendor/assets/javascripts. Nothing to out of the ordinary, but to compile them for production we use the following block in our config/application.rb:

  config.assets.precompile << Proc.new do |path|

    full_path       = Rails.application.assets.resolve(path).to_path

    app_assets_path = Rails.root.join('app', 'assets').to_path

    if full_path.starts_with? app_assets_path

      if File.basename(full_path) =~ /^[^_]+(.*)\.(css|js)\.?(sass|scss)?$/

        puts "\e[0;32m✓ #{full_path}\e[0m"

        true

      else

        puts "\e[1;30m✗ #{full_path}\e[0m"

        false

      end

    end

  end

All was well with this up until a package was added that had a bower.json file in it. The package in our case was requirejs-plugins. After adding this package in, during an asset compile we were greated with the following error:

Sprockets::FileNotFound: couldn't find file 'requirejs-plugins/bower.json'

When you look in vendor/assets/javascripts/requirejs-plugins you can clearly see there is a bower.json file, so what is the deal? It turns out Sprockets is to blame for this one, at least partially. To better explain I’ll include the code in question; which was 2.12.3 as of this writing.

  # Finds the expanded real path for a given logical path by

  # searching the environment's paths.

  #

  #     resolve("application.js")

  #     # => "/path/to/app/javascripts/application.js.coffee"

  #

  # A `FileNotFound` exception is raised if the file does not exist.

  def resolve(logical_path, options = {})

    # If a block is given, preform an iterable search

    if block_given?

      require 'pry'

      args = attributes_for(logical_path).search_paths + [options]

      @trail.find(*args) do |path|

        pathname = Pathname.new(path)

        if %w( .bower.json bower.json component.json ).include?(pathname.basename.to_s)

          bower = json_decode(pathname.read)

          case bower['main']

          when String

            yield pathname.dirname.join(bower['main'])

          when Array

            extname = File.extname(logical_path)

            bower['main'].each do |fn|

              if extname == "" || extname == File.extname(fn)

                yield pathname.dirname.join(fn)

              end

            end

          end

        else

          yield pathname

        end

      end

    else

      resolve(logical_path, options) do |pathname|

        return pathname

      end

      raise FileNotFound, "couldn't find file '#{logical_path}'"

    end

  end

Wow, what is going on here?? Well it turns out this is trying to resolve asset files for you. It has some pretty good smarts to it; however, when you pass it a bower.json file it attempts to match any assets defined in it that end in .json. This is where the the problem happens… there isn’t a .json file defined in the bower file.

To fix this I essentially had to catch the exception being raised in the do block:

  config.assets.precompile << Proc.new do |path|

    begin

      full_path       = Rails.application.assets.resolve(path).to_path

      app_assets_path = Rails.root.join('app', 'assets').to_path

      if full_path.starts_with? app_assets_path

        if File.basename(full_path) =~ /^[^_]+(.*)\.(css|js)\.?(sass|scss)?$/

          puts "\e[0;32m✓ #{full_path}\e[0m"

          true

        else

          puts "\e[1;30m✗ #{full_path}\e[0m"

          false

        end

      end

    rescue Sprockets::FileNotFound => e

      puts "\x1b[31m✗ #{e.message}\e[0m"

      false

    end

  end

This isn’t the best solution and I hope to do a touch of refactoring of this over the weekend to make that Sprockets::resolve method a little better.

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