Implemented Lotus::Utils::Kernel.Symbol

CHANGELOG.md

@@ -1,6 +1,8 @@
 ## v0.2.0
 ### Jun 23, 2014
 
+1894be5 2014-06-12 **Luca Guidi** Implemented Lotus::Utils::Kernel.Symbol
+
 13532f5 2014-06-13 **Luca Guidi** [breaking] Implemented Lotus::Utils::Callbacks::Chain#freeze in order to prevent modification after the object has been frozen
 
 e438da8 2014-06-13 **Luca Guidi** [breaking] All the Utils::Kernel methods will raise TypeError in case of failed coercion.

lib/lotus/utils/kernel.rb

@@ -841,6 +841,58 @@ def self.Pathname(arg)
       rescue NoMethodError
         raise TypeError.new "can't convert into Pathname"
       end
+
+      # Coerces the argument to be a String.
+      #
+      # @param arg [#to_sym] the argument
+      #
+      # @return [Symbol] the result of the coercion
+      #
+      # @raise [TypeError] if the argument can't be coerced
+      #
+      # @since 0.2.0
+      #
+      # @example Basic Usage
+      #   require 'lotus/utils/kernel'
+      #
+      #   Lotus::Utils::Kernel.Symbol(:hello)  # => :hello
+      #   Lotus::Utils::Kernel.Symbol('hello') # => :hello
+      #
+      # @example Symbol Interface
+      #   require 'lotus/utils/kernel'
+      #
+      #   class StatusSymbol
+      #     def to_sym
+      #       :success
+      #     end
+      #   end
+      #
+      #   Lotus::Utils::Kernel.Symbol(StatusSymbol.new) # => :success
+      #
+      # @example Unchecked Exceptions
+      #   require 'lotus/utils/kernel'
+      #
+      #   # When nil
+      #   input = nil
+      #   Lotus::Utils::Kernel.Symbol(input) # => TypeError
+      #
+      #   # When empty string
+      #   input = ''
+      #   Lotus::Utils::Kernel.Symbol(input) # => TypeError
+      #
+      #   # Missing #respond_to?
+      #   input = BasicObject.new
+      #   Lotus::Utils::Kernel.Symbol(input) # => TypeError
+      def self.Symbol(arg)
+        case arg
+        when '' then raise TypeError.new "can't convert into Symbol"
+        when ->(a) { a.respond_to?(:to_sym) } then arg.to_sym
+        else
+          raise TypeError.new "can't convert into Symbol"
+        end
+      rescue NoMethodError
+        raise TypeError.new "can't convert into Symbol"
+      end
     end
   end
 end

test/kernel_test.rb

@@ -2096,4 +2096,128 @@ def to_pathname
       end
     end
   end
+
+  describe '.Symbol' do
+    describe 'successful operations' do
+      before do
+        class StatusSymbol
+          def to_sym
+            :success
+          end
+        end
+
+        @result = Lotus::Utils::Kernel.Symbol(input)
+      end
+
+      after do
+        Object.send(:remove_const, :StatusSymbol)
+      end
+
+      describe 'when a symbol is given' do
+        let(:input) { :hello }
+
+        it 'returns a symbol' do
+          @result.must_equal :hello
+        end
+      end
+
+      describe 'when a string is given' do
+        let(:input) { 'hello' }
+
+        it 'returns a symbol' do
+          @result.must_equal :hello
+        end
+      end
+
+      describe 'when an object that implements #to_sym' do
+        let(:input) { StatusSymbol.new }
+
+        it 'returns a symbol' do
+          @result.must_equal :success
+        end
+      end
+    end
+
+    describe 'failure operations' do
+      describe "when nil is given" do
+        let(:input) { nil }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when empty string is given" do
+        let(:input) { '' }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when true is given" do
+        let(:input) { true }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when false is given" do
+        let(:input) { false }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when a number is given" do
+        let(:input) { 12 }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when a date is given" do
+        let(:input) { Date.today }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when a datetime is given" do
+        let(:input) { DateTime.now }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when a time is given" do
+        let(:input) { Time.now }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+      end
+
+      describe "when an object that doesn't implement #respond_to?" do
+        let(:input) { BasicObject.new }
+
+        it 'raises error' do
+          -> { Lotus::Utils::Kernel.Symbol(input) }.must_raise TypeError
+        end
+
+        it 'returns useful informations about the failure' do
+          begin
+            Lotus::Utils::Kernel.Symbol(input)
+          rescue => e
+            e.message.must_equal "can't convert into Symbol"
+          end
+        end
+      end
+    end
+  end
 end