HOW TO: Rails 4.2 add 'vendor/asset' to precompile list

precompile.md

To enable the precompilation of all non.js/.css assets within vendor/assets just add this to config/initializers/assets.rb:

Rails.application.config.assets.precompile << Proc.new { |path, fn| fn =~ /vendor\/assets/ && !%w(.js .css).include?(File.extname(path)) }

Be aware that this will precompile ALL non .js/.css assets that you have there, some plugins or libraries might have .txt or other files around, and those would end up into your precompiled list also.

If you need to precompile images only, you could use this:

Rails.application.config.assets.precompile += %w(*.png *.jpg *.jpeg *.gif)
# or this
Rails.application.config.assets.precompile << /\.(?:png|jpg|jpeg|gif)\z/

If you need to precompile fonts only, you could use this:

Rails.application.config.assets.precompile += %w(*.svg *.eot *.woff *.ttf)
# or this
Rails.application.config.assets.precompile << /\.(?:svg|eot|woff|ttf)\z/

If you would like to precompile everything within vendor/assets/images:

Rails.application.config.assets.precompile << Proc.new { |path, fn| fn =~ /vendor\/assets\/images/ }