ERB Filter

lib/rake-pipeline-web-filters.rb

@@ -26,4 +26,5 @@ module Filters
 require "rake-pipeline-web-filters/chained_filter"
 require "rake-pipeline-web-filters/less_filter"
 require "rake-pipeline-web-filters/handlebars_filter"
+require "rake-pipeline-web-filters/erb_filter"
 require "rake-pipeline-web-filters/helpers"

lib/rake-pipeline-web-filters/erb_filter.rb

@@ -0,0 +1,49 @@
+require 'rake-pipeline-web-filters/filter_with_dependencies'
+
+module Rake::Pipeline::Web::Filters
+  # Evalute each file as an ERB template
+  #
+  # @example
+  #   !!!ruby
+  #   Rake::Pipeline.build do
+  #     input "app/assets", "**/*.js.erb"
+  #     output "public"
+  #
+  #     # Compile each JS file under the app/assets
+  #     # directory as an ERB template
+  #     filter Rake::Pipeline::Web::Filters::ErbFilter
+  #   end
+  class ErbFilter < Rake::Pipeline::Filter
+    include Rake::Pipeline::Web::Filters::FilterWithDependencies
+
+    # @param [Binding] binding to evaluate the template in
+    # @param [Proc] block a block to use as the Filter's
+    #   {#output_name_generator}.
+    def initialize(binding = binding, &block)
+      @binding = binding
+      block ||= proc { |input| input.gsub(/\.erb$/, '') }
+      super(&block)
+    end
+
+    # Implement the {#generate_output} method required by
+    # the {Filter} API. Parses each file as an ERB template
+    # and evaluates it against the {binding}
+    #
+    # @param [Array<FileWrapper>] inputs an Array of
+    #   {FileWrapper} objects representing the inputs to
+    #   this filter.
+    # @param [FileWrapper] output a single {FileWrapper}
+    #   object representing the output.
+    def generate_output(inputs, output)
+      inputs.each do |input|
+        output.write ERB.new(input.read).result(@binding)
+      end
+    end
+
+    private
+
+      def external_dependencies
+        [ 'erb' ]
+      end
+  end
+end

lib/rake-pipeline-web-filters/helpers.rb

@@ -98,6 +98,12 @@ def less(*args, &block)
     def handlebars(*args, &block)
       filter(Rake::Pipeline::Web::Filters::HandlebarsFilter, *args, &block)
     end
+    #
+    # Add a new {ErbFilter} to the pipeline.
+    # @see ErbFilter#initialize
+    def erb(*args, &block)
+      filter(Rake::Pipeline::Web::Filters::ErbFilter, *args, &block)
+    end
   end
 
   module ProjectHelpers

spec/erb_filter_spec.rb

@@ -0,0 +1,47 @@
+describe "ErbFilter" do
+  ErbFilter ||= Rake::Pipeline::Web::Filters::ErbFilter
+  MemoryFileWrapper ||= Rake::Pipeline::SpecHelpers::MemoryFileWrapper
+  User = Struct.new(:name)
+
+  let(:input) { "<%= user.name %>" }
+  let(:user) { User.new "Adam" } 
+
+  def input_file(name, content)
+    MemoryFileWrapper.new("/path/to/input", name, "UTF-8", content)
+  end
+
+  def output_file(name)
+    MemoryFileWrapper.new("/path/to/output", name, "UTF-8")
+  end
+
+  def setup_filter(filter)
+    filter.file_wrapper_class = MemoryFileWrapper
+    filter.input_files = [input_file("test.html.erb", input)]
+    filter.output_root = "/path/to/output"
+    filter.rake_application = Rake::Application.new
+    filter
+  end
+
+  it "generates output" do
+    filter = setup_filter ErbFilter.new(binding)
+    filter.output_files.should == [output_file("test.html")]
+    tasks = filter.generate_rake_tasks
+    tasks.each(&:invoke)
+
+    file = MemoryFileWrapper.files["/path/to/output/test.html"]
+    file.body.should == user.name
+    file.encoding.should == "UTF-8"
+  end
+
+  describe "naming output files" do
+    it "strips .erb extensions by default" do
+      filter = setup_filter ErbFilter.new
+      filter.output_files.first.path.should == "test.html"
+    end
+
+    it "accepts a block to customize output file names" do
+      filter = setup_filter(ErbFilter.new { |input| "octopus" })
+      filter.output_files.first.path.should == "octopus"
+    end
+  end
+end

spec/helpers_spec.rb

@@ -102,6 +102,13 @@ def filter
       filter.should be_kind_of(Rake::Pipeline::Web::Filters::HandlebarsFilter)
     end
   end
+
+  describe "#erb" do
+    it "creates ErbFilter" do
+      dsl.erb
+      filter.should be_kind_of(Rake::Pipeline::Web::Filters::ErbFilter)
+    end
+  end
 end
 
 describe "ProjectHelpers" do