Add context() DSL for config classes

2 files changed, 98 insertions, 0 deletions

diff --git a/lib/mixlib/config.rb b/lib/mixlib/config.rb
index 6819b38..28a22b9 100644
--- a/lib/mixlib/config.rb
+++ b/lib/mixlib/config.rb
@@ -26,8 +26,10 @@ module Mixlib
     def self.extended(base)
       class << base; attr_accessor :configuration; end
       class << base; attr_accessor :configurables; end
+      class << base; attr_accessor :contexts; end
       base.configuration = Hash.new
       base.configurables = Hash.new
+      base.contexts = Array.new
     end
 
     # Loads a given ruby file, and runs instance_eval against it in the context of the current
@@ -98,6 +100,7 @@ module Mixlib
     # Resets all config options to their defaults.
     def reset
       self.configuration = Hash.new
+      self.contexts.each { |context| context.reset }
     end
 
     # Merge an incoming hash with our config options
@@ -182,6 +185,31 @@ module Mixlib
       configurables[symbol]
     end
 
+    # Allows you to create a new config context where you can define new
+    # options with default values.
+    #
+    # For example:
+    #
+    # context :server_info do
+    #   configurable(:url).defaults_to("http://localhost")
+    # end
+    #
+    # === Parameters
+    # symbol<Symbol>: the name of the context
+    # block<Block>: a block that will be run in the context of this new config
+    # class.
+    def context(symbol, &block)
+      context = Class.new
+      context.extend(::Mixlib::Config)
+      contexts << context
+      if block
+        context.instance_eval(&block)
+      end
+      configurable(symbol).defaults_to(context).writes_value do |value|
+        raise "config context #{symbol} cannot be modified"
+      end
+    end
+
     # Allows for simple lookups and setting of config options via method calls
     # on Mixlib::Config.  If there any arguments to the method, they are used to set
     # the value of the config option.  Otherwise, it's a simple get operation.
diff --git a/spec/mixlib/config_spec.rb b/spec/mixlib/config_spec.rb
index 420e36f..4e141c8 100644
--- a/spec/mixlib/config_spec.rb
+++ b/spec/mixlib/config_spec.rb
@@ -311,4 +311,74 @@ describe Mixlib::Config do
       @klass.attr.should == 4
     end
   end
+
+  describe "When a configurable exists with a context" do
+    before :each do
+      @klass = Class.new
+      @klass.extend(::Mixlib::Config)
+      @klass.class_eval do
+        context(:blah) do
+          default :x, 5
+        end
+      end
+    end
+
+    it "configurable defaults in that context work" do
+      @klass.blah.x.should == 5
+    end
+
+    it "after setting values in the context, the values remain set" do
+      @klass.blah.x = 10
+      @klass.blah.x.should == 10
+    end
+
+    it "setting values with the same name in the parent context do not affect the child context" do
+      @klass.x = 10
+      @klass.x.should == 10
+      @klass.blah.x.should == 5
+    end
+
+    it "after reset of the parent class, children are reset" do
+      @klass.blah.x = 10
+      @klass.blah.x.should == 10
+      @klass.reset
+      @klass.blah.x.should == 5
+    end
+  end
+
+  describe "When a configurable exists with a nested context" do
+    before :each do
+      @klass = Class.new
+      @klass.extend(::Mixlib::Config)
+      @klass.class_eval do
+        context(:blah) do
+          context(:yarr) do
+            default :x, 5
+          end
+        end
+      end
+    end
+
+    it "configurable defaults in that context work" do
+      @klass.blah.yarr.x.should == 5
+    end
+
+    it "after setting values in the context, the values remain set" do
+      @klass.blah.yarr.x = 10
+      @klass.blah.yarr.x.should == 10
+    end
+
+    it "setting values with the same name in the parent context do not affect the child context" do
+      @klass.x = 10
+      @klass.x.should == 10
+      @klass.blah.yarr.x.should == 5
+    end
+
+    it "after reset of the parent class, children are reset" do
+      @klass.blah.yarr.x = 10
+      @klass.blah.yarr.x.should == 10
+      @klass.reset
+      @klass.blah.yarr.x.should == 5
+    end
+  end
 end