1 files changed, 88 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/json/backends/yaml.rb b/activesupport/lib/active_support/json/backends/yaml.rb
new file mode 100644
index 0000000000..667016f45d
--- /dev/null
+++ b/activesupport/lib/active_support/json/backends/yaml.rb
@@ -0,0 +1,88 @@
+require 'active_support/core_ext/string/starts_ends_with'
+
+module ActiveSupport
+  module JSON
+    unless const_defined?(:ParseError)
+      class ParseError < StandardError
+      end
+    end
+
+    module Backends
+      module Yaml
+        extend self
+
+        # Parses a JSON string or IO and converts it into an object
+        def decode(json)
+          if json.respond_to?(:read)
+            json = json.read
+          end
+          YAML.load(convert_json_to_yaml(json))
+        rescue ArgumentError => e
+          raise ParseError, "Invalid JSON string"
+        end
+    
+        protected
+          # Ensure that ":" and "," are always followed by a space
+          def convert_json_to_yaml(json) #:nodoc:
+            require 'strscan' unless defined? ::StringScanner
+            scanner, quoting, marks, pos, times = ::StringScanner.new(json), false, [], nil, []
+            while scanner.scan_until(/(\\['"]|['":,\\]|\\.)/)
+              case char = scanner[1]
+              when '"', "'"
+                if !quoting
+                  quoting = char
+                  pos = scanner.pos
+                elsif quoting == char
+                  if json[pos..scanner.pos-2] =~ DATE_REGEX
+                    # found a date, track the exact positions of the quotes so we can remove them later.
+                    # oh, and increment them for each current mark, each one is an extra padded space that bumps
+                    # the position in the final YAML output
+                    total_marks = marks.size
+                    times << pos+total_marks << scanner.pos+total_marks
+                  end
+                  quoting = false
+                end
+              when ":",","
+                marks << scanner.pos - 1 unless quoting
+              end
+            end
+
+            if marks.empty?
+              json.gsub(/\\([\\\/]|u[[:xdigit:]]{4})/) do
+                ustr = $1
+                if ustr.start_with?('u')
+                  [ustr[1..-1].to_i(16)].pack("U")
+                elsif ustr == '\\'
+                  '\\\\'
+                else
+                  ustr
+                end
+              end
+            else
+              left_pos  = [-1].push(*marks)
+              right_pos = marks << scanner.pos + scanner.rest_size
+              output    = []
+              left_pos.each_with_index do |left, i|
+                scanner.pos = left.succ
+                output << scanner.peek(right_pos[i] - scanner.pos + 1).gsub(/\\([\\\/]|u[[:xdigit:]]{4})/) do
+                  ustr = $1
+                  if ustr.start_with?('u')
+                    [ustr[1..-1].to_i(16)].pack("U")
+                  elsif ustr == '\\'
+                    '\\\\'
+                  else
+                    ustr
+                  end
+                end
+              end
+              output = output * " "
+
+              times.each { |i| output[i-1] = ' ' }
+              output.gsub!(/\\\//, '/')
+              output
+            end
+          end
+      end
+    end
+  end
+end