Add support for --[no]-thing explicit boolean flags.

lib/samovar/flags.rb

@@ -8,7 +8,7 @@ class Flags
 		def initialize(text)
 			@text = text
 
-			@ordered = text.split(/\s+\|\s+/).map{|part| Flag.new(part)}
+			@ordered = text.split(/\s+\|\s+/).map{|part| Flag.parse(part)}
 		end
 
 		def each(&block)
@@ -21,20 +21,21 @@ def first
 
 		# Whether or not this flag should have a true/false value if not specified otherwise.
 		def boolean?
-			@ordered.count == 1 and @ordered.first.value.nil?
+			@ordered.count == 1 and @ordered.first.boolean?
 		end
 
 		def count
 			return @ordered.count
 		end
 
 		def to_s
-			'[' + @ordered.join(' | ') + ']'
+			"[#{@ordered.join(' | ')}]"
 		end
 
 		def parse(input)
 			@ordered.each do |flag|
-				if result = flag.parse(input)
+				result = flag.parse(input)
+				if result != nil
 					return result
 				end
 			end
@@ -44,45 +45,93 @@ def parse(input)
 	end
 
 	class Flag
-		def initialize(text)
-			@text = text
-
+		def self.parse(text)
 			if text =~ /(.*?)\s(\<.*?\>)/
-				@prefix = $1
-				@value = $2
+				ValueFlag.new(text, $1, $2)
+			elsif text =~ /--\[no\]-(.*?)$/
+				BooleanFlag.new(text, "--#{$1}")
 			else
-				@prefix = @text
-				@value = nil
+				ValueFlag.new(text, text, nil)
 			end
-
-			*@alternatives, @prefix = @prefix.split('/')
+		end
+
+		def initialize(text, prefix, alternatives = nil)
+			@text = text
+			@prefix = prefix
+			@alternatives = alternatives
 		end
 
 		attr :text
 		attr :prefix
 		attr :alternatives
-		attr :value
 
 		def to_s
 			@text
 		end
 
-		def prefix?(token)
-			@prefix == token or @alternatives.include?(token)
-		end
-
 		def key
 			@key ||= @prefix.sub(/^-*/, '').gsub('-', '_').to_sym
 		end
 
+		def boolean?
+			false
+		end
+	end
+
+	class ValueFlag < Flag
+		def initialize(text, prefix, value)
+			super(text, prefix)
+
+			@value = value
+
+			*@alternatives, @prefix = @prefix.split('/')
+		end
+
+		attr :alternatives
+		attr :value
+
+		def boolean?
+			@value.nil?
+		end
+
+		def prefix?(token)
+			@prefix == token or @alternatives.include?(token)
+		end
+
 		def parse(input)
 			if prefix?(input.first)
 				if @value
-					input.shift(2).last
+					return input.shift(2).last
 				else
-					input.shift; key
+					input.shift
+					return key
 				end
 			end
 		end
 	end
+
+	class BooleanFlag < Flag
+		def initialize(text, prefix, value = nil)
+			super(text, prefix)
+
+			@value = value
+
+			@negated = @prefix.sub(/^--/, '--no-')
+			@alternatives = [@negated]
+		end
+
+		def prefix?(token)
+			@prefix == token or @negated == token
+		end
+
+		def parse(input)
+			if input.first == @prefix
+				input.shift
+				return true
+			elsif input.first == @negated
+				input.shift
+				return false
+			end
+		end
+	end
 end

lib/samovar/option.rb

@@ -66,7 +66,8 @@ def coerce(result)
 		end
 
 		def parse(input, parent = nil, default = nil)
-			if result = @flags.parse(input)
+			result = @flags.parse(input)
+			if result != nil
 				@value.nil? ? coerce(result) : @value
 			elsif default ||= @default
 				return default

lib/samovar/options.rb

@@ -90,7 +90,9 @@ def parse(input, parent = nil, default = nil)
 			values = (default || @defaults).dup
 
 			while option = @keyed[input.first]
-				if result = option.parse(input)
+				prefix = input.first
+				result = option.parse(input)
+				if result != nil
 					values[option.key] = result
 				end
 			end

lib/samovar/table.rb

@@ -76,8 +76,9 @@ def parse(input, parent)
 
 				current = parent.send(key)
 
-				if result = row.parse(input, parent, current)
-					parent.send("#{row.key}=", result)
+				result = row.parse(input, parent, current)
+				if result != nil
+					parent.public_send("#{row.key}=", result)
 				end
 			end
 		end

test/samovar/command.rb

@@ -20,6 +20,7 @@ class Top < Samovar::Command
 		option '-c/--configuration <name>', "Specify a specific build configuration.", default: 'TEAPOT_CONFIGURATION'
 		option '-i/--in/--root <path>', "Work in the given root directory."
 		option '--verbose | --quiet', "Verbosity of output for debugging.", key: :logging
+		option '--[no]-color', "Enable or disable color output.", default: true
 		option '-h/--help', "Print out help information."
 		option '-v/--version', "Print out the application version."
 	end
@@ -81,4 +82,21 @@ class Top < Samovar::Command
 			expect(buffer.string).to be(:include?, Top.description)
 		end
 	end
+
+	with '--[no]-color flag' do
+		it "should use default color output if unspecified" do
+			top = Top[]
+			expect(top.options[:color]).to be == true
+		end
+
+		it "should enable color output" do
+			top = Top['--color']
+			expect(top.options[:color]).to be == true
+		end
+
+		it "should disable color output" do
+			top = Top['--no-color']
+			expect(top.options[:color]).to be == false
+		end
+	end
 end