add is_default? inspection method

plus some code cleanup of the configurable class

Signed-off-by: Lamont Granquist <lamont@scriptkiddie.org>

4 files changed, 80 insertions, 23 deletions

diff --git a/README.md b/README.md
index 2deb9d3..1a1121c 100644
--- a/README.md
+++ b/README.md
@@ -248,6 +248,18 @@ This allows the user to quickly specify a number of values with one default, whi
   print_network_requests false
 ```
 
+You can also inspect if the values are still their defaults or not:
+
+```ruby
+MyConfig.is_default?(:verbosity)  # == true
+MyConfig[:verbosity] = 5
+MyConfig.is_default?(:verbosity)  # == false
+MyConfig[:verbosity] = 1
+MyConfig.is_default?(:verbosity)  # == true
+```
+
+Trying to call `is_default?` on a config context or a config which does not have a declared default is an error and will raise.
+
 ## Strict Mode
 
 Misspellings are a common configuration problem, and Mixlib::Config has an answer: `config_strict_mode`. Setting `config_strict_mode` to `true` will cause any misspelled or incorrect configuration option references to throw `Mixlib::Config::UnknownConfigOptionError`.
diff --git a/lib/mixlib/config.rb b/lib/mixlib/config.rb
index 6a935ae..adb8bbf 100644
--- a/lib/mixlib/config.rb
+++ b/lib/mixlib/config.rb
@@ -158,6 +158,17 @@ module Mixlib
 
     alias_method :has_key?, :key?
 
+    def is_default?(key)
+      pp configurables
+      pp configuration
+      symbol = key.to_sym
+      if configurables.has_key?(symbol)
+        configurables[symbol].is_default?(configuration)
+      else
+        raise ArgumentError, "config option must exist, and not be a context to check for default values"
+      end
+    end
+
     # Resets a config option to its default.
     #
     # === Parameters
diff --git a/lib/mixlib/config/configurable.rb b/lib/mixlib/config/configurable.rb
index e1b5b14..df2ffd9 100644
--- a/lib/mixlib/config/configurable.rb
+++ b/lib/mixlib/config/configurable.rb
@@ -1,6 +1,6 @@
 #
 # Author:: John Keiser (<jkeiser@chef.io>)
-# Copyright:: Copyright (c) 2013-2016 Chef Software, Inc.
+# Copyright:: Copyright (c) 2013-2018, Chef Software Inc.
 # License:: Apache License, Version 2.0
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -19,20 +19,31 @@
 module Mixlib
   module Config
     class Configurable
+      attr_reader :symbol
+      attr_reader :default_value
+      attr_reader :default_block
+
       def initialize(symbol)
         @symbol = symbol
-        @default_block = nil
-        @has_default = false
-        @default_value = nil
-        @writes_value = nil
       end
 
-      attr_reader :has_default
+      def has_default?
+        instance_variable_defined?(:@default_value)
+      end
+
+      def writes_value?
+        instance_variable_defined?(:@writes_value)
+      end
+
+      def default_block?
+        instance_variable_defined?(:@default_block)
+      end
+
+      alias_method :has_default, :has_default?
 
       def defaults_to(default_value = nil, &block)
-        @has_default = true
-        @default_block = block
         @default_value = default_value
+        @default_block = block if block_given?
         self
       end
 
@@ -42,32 +53,38 @@ module Mixlib
       end
 
       def get(config)
-        if config.has_key?(@symbol)
-          config[@symbol]
-        elsif @default_block
-          @default_block.call
+        if config.key?(symbol)
+          config[symbol]
+        elsif default_block?
+          default_block.call
         else
-          begin
-            # Some things cannot be dup'd, and you won't know this till after the fact
-            # because all values implement dup
-            config[@symbol] = @default_value.dup
-          rescue TypeError
-            @default_value
-          end
+          config[symbol] = safe_dup(default_value)
         end
       end
 
       def set(config, value)
-        config[@symbol] = @writes_value ? @writes_value.call(value) : value
+        config[symbol] = writes_value? ? @writes_value.call(value) : value
       end
 
       def default
-        if @default_block
-          @default_block.call
+        if default_block?
+          default_block.call
         else
-          @default_value
+          default_value
         end
       end
+
+      def is_default?(config)
+        !config.key?(symbol) || config[symbol] == default_value
+      end
+
+      private
+
+      def safe_dup(e)
+        e.dup
+      rescue TypeError
+        e
+      end
     end
   end
 end
diff --git a/spec/mixlib/config_spec.rb b/spec/mixlib/config_spec.rb
index c664ceb..1786789 100644
--- a/spec/mixlib/config_spec.rb
+++ b/spec/mixlib/config_spec.rb
@@ -235,6 +235,23 @@ describe Mixlib::Config do
       expect(@klass.respond_to?("z=".to_sym)).to be false
     end
 
+    it "returns true for is_default? for a default value" do
+      expect(@klass[:a]).to eql(1)
+      expect(@klass.is_default?(:a)).to be true
+    end
+
+    it "returns true for is_default? for an overwritten default value" do
+      @klass[:a] = 1
+      expect(@klass[:a]).to eql(1)
+      expect(@klass.is_default?(:a)).to be true
+    end
+
+    it "returns false for is_default? for a value that is not the default" do
+      @klass[:a] = 2
+      expect(@klass[:a]).to eql(2)
+      expect(@klass.is_default?(:a)).to be false
+    end
+
     describe "and extra methods have been dumped into Object" do
       class NopeError < StandardError
       end