1 files changed, 85 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/ordered_options.rb b/activesupport/lib/active_support/ordered_options.rb
new file mode 100644
index 0000000000..c4e419f546
--- /dev/null
+++ b/activesupport/lib/active_support/ordered_options.rb
@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/object/blank"
+
+module ActiveSupport
+  # Usually key value pairs are handled something like this:
+  #
+  #   h = {}
+  #   h[:boy] = 'John'
+  #   h[:girl] = 'Mary'
+  #   h[:boy]  # => 'John'
+  #   h[:girl] # => 'Mary'
+  #   h[:dog]  # => nil
+  #
+  # Using +OrderedOptions+, the above code could be reduced to:
+  #
+  #   h = ActiveSupport::OrderedOptions.new
+  #   h.boy = 'John'
+  #   h.girl = 'Mary'
+  #   h.boy  # => 'John'
+  #   h.girl # => 'Mary'
+  #   h.dog  # => nil
+  #
+  # To raise an exception when the value is blank, append a
+  # bang to the key name, like:
+  #
+  #   h.dog! # => raises KeyError: :dog is blank
+  #
+  class OrderedOptions < Hash
+    alias_method :_get, :[] # preserve the original #[] method
+    protected :_get # make it protected
+
+    def []=(key, value)
+      super(key.to_sym, value)
+    end
+
+    def [](key)
+      super(key.to_sym)
+    end
+
+    def method_missing(name, *args)
+      name_string = name.to_s
+      if name_string.chomp!("=")
+        self[name_string] = args.first
+      else
+        bangs = name_string.chomp!("!")
+
+        if bangs
+          self[name_string].presence || raise(KeyError.new(":#{name_string} is blank"))
+        else
+          self[name_string]
+        end
+      end
+    end
+
+    def respond_to_missing?(name, include_private)
+      true
+    end
+  end
+
+  # +InheritableOptions+ provides a constructor to build an +OrderedOptions+
+  # hash inherited from another hash.
+  #
+  # Use this if you already have some hash and you want to create a new one based on it.
+  #
+  #   h = ActiveSupport::InheritableOptions.new({ girl: 'Mary', boy: 'John' })
+  #   h.girl # => 'Mary'
+  #   h.boy  # => 'John'
+  class InheritableOptions < OrderedOptions
+    def initialize(parent = nil)
+      if parent.kind_of?(OrderedOptions)
+        # use the faster _get when dealing with OrderedOptions
+        super() { |h, k| parent._get(k) }
+      elsif parent
+        super() { |h, k| parent[k] }
+      else
+        super()
+      end
+    end
+
+    def inheritable_copy
+      self.class.new(self)
+    end
+  end
+end