Provide a dir => extension API to file update checker.

1 files changed, 41 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/file_update_checker.rb b/activesupport/lib/active_support/file_update_checker.rb
index da96d3e64d..77bc5388d6 100644
--- a/activesupport/lib/active_support/file_update_checker.rb
+++ b/activesupport/lib/active_support/file_update_checker.rb
@@ -1,3 +1,6 @@
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/array/extract_options"
+
 module ActiveSupport
   # This class is responsible to track files and invoke the given block
   # whenever one of these files are changed. For example, this class
@@ -15,15 +18,34 @@ module ActiveSupport
   class FileUpdateChecker
     attr_reader :paths, :last_update_at
 
+    # It accepts two parameters on initialization. The first is
+    # the *paths* and the second is *calculate*, a boolean.
+    #
+    # paths must be an array of file paths but can contain a hash as
+    # last argument. The hash must have directories as keys and the
+    # value is an array of extensions to be watched under that directory.
+    #
+    # If *calculate* is true, the latest updated at will calculated
+    # on initialization, therefore, the first call to execute_if_updated
+    # will only evaluate the block if something really changed.
+    #
+    # This method must also receive a block that will be the block called
+    # once a file changes.
+    #
+    # This particular implementation checks for added files and updated files,
+    # but not removed files. Directories lookup are compiled to a glob for
+    # performance.
     def initialize(paths, calculate=false, &block)
       @paths = paths
+      @glob  = compile_glob(@paths.extract_options!)
       @block = block
       @last_update_at = calculate ? updated_at : nil
     end
 
     def updated_at
-      # TODO: Use Enumerable check once we get rid of 1.8.7
-      all = paths.is_a?(Array) ? paths : Dir[paths]
+      all = []
+      all.concat @paths
+      all.concat Dir[@glob] if @glob
       all.map { |path| File.mtime(path) }.max
     end
 
@@ -37,5 +59,22 @@ module ActiveSupport
         false
       end
     end
+
+    private
+
+    def compile_glob(hash)
+      return if hash.empty?
+      globs = []
+      hash.each do |key, value|
+        globs << "#{key}/**/*#{compile_ext(value)}"
+      end
+      "{#{globs.join(",")}}"
+    end
+
+    def compile_ext(array)
+      array = Array.wrap(array)
+      return if array.empty?
+      ".{#{array.join(",")}}"
+    end
   end
 end