Added support for a dynamic preamble.

README.md

@@ -154,6 +154,14 @@ and `#option!` (to set the value to true):
 * `bin_path` – The path to the `node` executable if non-standard and not using `therubyracer`.
 * All of the hook methods mentioned below.
 
+### Custom Preamble
+
+You can generate a custom preamble using a code block. For example, you can replace the location of the original `.coffee` file by a relative one to `Rails.root`.
+
+    Barista.add_preamble do |location|
+        "/* : DO NOT MODIFY - compiled from #{Pathname.new(location).relative_path_from(Rails.root).to_s}\n\n"
+    end
+
 ## Frameworks
 
 One of the other main features Barista adds (over other tools) is frameworks similar

lib/barista.rb

@@ -46,6 +46,10 @@ def on_hook(name, *args, &blk)
     def invoke_hook(name, *args)
       hooks.invoke(name, *args)
     end
+
+    def has_hook?(name)
+      hooks.has_hook?(name)
+    end
 
     has_hook_method :on_compilation_error        => :compilation_failed,
                     :on_compilation              => :compiled,
@@ -54,14 +58,24 @@ def invoke_hook(name, *args)
                     :before_full_compilation     => :before_full_compilation,
                     :before_compilation          => :before_compilation
 
-
     # Configuration - Tweak how you use Barista.
 
-    has_boolean_options    :verbose, :bare, :add_filter, :add_preamble, :exception_on_error, :embedded_interpreter, :auto_compile
+    has_boolean_options    :verbose, :bare, :add_filter, :exception_on_error, :embedded_interpreter, :auto_compile, :add_preamble
     has_delegate_methods   Compiler, :bin_path, :bin_path=, :js_path, :js_path=
     has_delegate_methods   Framework, :register
     has_deprecated_methods :compiler, :compiler=, :compiler_klass, :compiler_klass=
 
+    def add_preamble(&blk)
+      self.add_preamble = true
+      if block_given?
+        @preamble = blk
+      end
+    end
+
+    def preamble
+      @preamble
+    end
+
     def configure
       yield self if block_given?
     end
@@ -159,10 +173,6 @@ def default_for_add_filter
       local_env?
     end
 
-    def default_for_add_preamble
-      local_env?
-    end
-
     def default_for_exception_on_error
       true
     end

lib/barista/compiler.rb

@@ -114,7 +114,7 @@ def compile!
       @compiled_content = preamble(location) + @compiled_content if location != 'inline' && Barista.add_preamble?
       @compiled         = true
     end
-
+    
     def to_js
       compile! unless defined?(@compiled) && @compiled
       @compiled_content
@@ -159,7 +159,11 @@ def save(path = @options[:output_path])
 
     def preamble(location)
       inner_message = copyable?(location) ? "copied" : "compiled"
-      "/* DO NOT MODIFY. This file was #{inner_message} #{Time.now.httpdate} from\n * #{location.strip}\n */\n\n"
+      if Barista.preamble
+        Barista.preamble.call(location)
+      else
+        "/* DO NOT MODIFY. This file was #{inner_message} #{Time.now.httpdate} from\n * #{location.strip}\n */\n\n"
+      end
     end
 
     def compilation_error_for(location, message)

lib/barista/hooks.rb

@@ -16,5 +16,9 @@ def invoke(name, *args)
       nil
     end
 
+    def has_hook?(name)
+      @callbacks.has_key?(name)
+    end
+
   end
-end
+end

spec/barista_spec.rb

@@ -12,4 +12,4 @@
 
   context 'compiling all'
 
-end
+end