Retry on random mutates that are the same

* This fixes problems where generated mutations have a chance
  to be the same like the mutation subject.

TODO

@@ -17,6 +17,6 @@
   It can be used to make sure each literal value is touched.
 * Replace nil or add "do not touch me object" to literal mutations.
 * Add remaining literals
-* Mutate options for Regexp literals
+* Mutate options on Regexp literals
 * Move Mutant.random_* into Mutant::Random namespace.
 * Use inheritable alias once (virtus,veritas,mapper,session, ...) support gem is born.

lib/mutant/mutator/fixnum_literal.rb

@@ -14,7 +14,9 @@ module Mutant
         generator << new_self(0)
         generator << new_self(1)
         generator << new_self(-node.value)
-        generator << new_self(Mutant.random_fixnum)
+        generator.generate do
+          new_self(Mutant.random_fixnum)
+        end
       end
     end
   end

lib/mutant/mutator/float_literal.rb

@@ -14,7 +14,9 @@ module Mutant
         generator << new_self(0.0)
         generator << new_self(1.0)
         generator << new_self(-node.value)
-        generator << new_self(Mutant.random_float)
+        generator.generate do
+          new_self(Mutant.random_float)
+        end
         generator << infinity
         generator << neg_infinity
         generator << nan

lib/mutant/mutator/generator.rb

@@ -1,22 +1,94 @@
 module Mutant
   class Mutator
     class Generator
-      def initialize(node,block)
-        @sexp,@block = node.to_sexp,block
-      end
 
+      # Append node to generated mutations if node does not equal orignal node
+      #
+      # @param [Rubinius::AST::Node] node
+      #
+      # @return [self]
+      #
+      # @api private
+      #
       def append(node)
-        return if same_node?(node)
+        return self unless new?(node)
         @block.call(node)
       end
 
       # FIXME: Use interhitable alias once in support gem.
       alias :<< :append
 
+      # Maximum amount of tries to generate a new node
+      MAX_TRIES = 3
+
+      # Call block until it generates a new AST node
+      #
+      # The primary use of this method is to give the random generated AST nodes
+      # a nice interface for retring generation when generation accidentally generated the
+      # same AST that is about to be mutated.
+      #
+      # @yield 
+      #   Execute block until AST node that does not equal wrapped node is generated by block
+      #
+      # @return [self]
+      #
+      # @raise [RuntimeError]
+      #   raises RuntimeError in case no new ast node can be generated after MAX_TRIES.
+      #
+      # @api private
+      #
+      def generate
+        MAX_TRIES.times do 
+          node = yield
+          return call(node) if new?(node)
+        end
+
+        raise "New AST could not be generated after #{MAX_TRIES} attempts"
+      end
+
     private
 
-      def same_node?(node)
-        @sexp == node.to_sexp
+      # Initialize generator
+      #
+      # @param [Rubinius::AST::Node] node
+      # @param [#call(node)] block
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def initialize(node,block)
+        @sexp,@block = node.to_sexp,block
+      end
+
+      # Call block with node
+      # 
+      # @param [Rubinius::AST::Node] node
+      #
+      # @return [self]
+      #
+      # @api private
+      #
+      def call(node)
+        @block.call(node)
+
+        self
+      end
+
+      # Check if node does not equal original node
+      #
+      # @param [Rubinius::AST::Node] node
+      #
+      # @return [true]
+      #   returns true when node is differend from the node to be mutated
+      #
+      # @return [false]
+      #   returns false otherwise
+      #
+      # @api private
+      #
+      def new?(node)
+        @sexp != node.to_sexp
       end
     end
   end

lib/mutant/mutator/string_literal.rb

@@ -13,7 +13,9 @@ module Mutant
       #
       def mutants(generator)
         generator << new_nil
-        generator << new_self(Mutant.random_hex_string)
+        generator.generate do
+          new_self(Mutant.random_hex_string)
+        end
       end
     end
   end

lib/mutant/mutator/symbol_literal.rb

@@ -11,7 +11,9 @@ module Mutant
       #
       def mutants(generator)
         generator << new_nil
-        generator << new(Rubinius::AST::SymbolLiteral,Mutant.random_hex_string.to_sym)
+        generator.generate do
+          new_self(Mutant.random_hex_string.to_sym)
+        end
       end
     end
   end

lib/mutant/mutator/true_literal.rb

@@ -12,7 +12,7 @@ module Mutant
       # @return [undefined]
       #
       def mutants(generator)
-        generator << new(Rubinius::AST::NilLiteral)
+        generator << new_ni
         generator << new(Rubinius::AST::FalseLiteral)
       end
     end

spec/unit/mutant/mutator/each_spec.rb

@@ -93,6 +93,21 @@ describe Mutant::Mutator, '#each' do
     it_should_behave_like 'a mutation enumerator method'
   end
 
+  context 'interpolated string literal (DynamicString)' do
+    let(:source) { '"foo#{1}bar"' }
+
+    let(:mutations) do
+      mutations = []
+      mutations << 'nil'
+    end
+
+    before do
+      Mutant.stub(:random_hex_string => random_string)
+    end
+
+    it_should_behave_like 'a mutation enumerator method'
+  end
+
   context 'fixnum literal' do
     let(:source) { '10' }
 
@@ -235,6 +250,32 @@ describe Mutant::Mutator, '#each' do
     it_should_behave_like 'a mutation enumerator method'
   end
 
+  context 'regexp literal' do
+    let(:source) { '/foo/' }
+
+    let(:base_mutations) do
+      mutations = []
+      mutations << 'nil'
+      mutations << "/#{random_string}/"
+    end
+
+    before do
+      Mutant.stub(:random_hex_string => random_string)
+    end
+
+    let(:mutations) { base_mutations }
+
+    it_should_behave_like 'a mutation enumerator method'
+
+   #it 'when source is empty regexp' do
+   #  let(:source) { '//' }
+
+   #  let(:mutations) { base_mutations - [source.to_ast] }
+
+   #  it_should_behave_like 'a mutation enumerator method'
+   #end
+  end
+
   context 'block literal' do
     let(:source) { "true\nfalse" }
 

spec/unit/mutant/mutator/generator/generate_spec.rb

@@ -0,0 +1,43 @@
+require 'spec_helper'
+
+describe Mutant::Mutator::Generator,'#generate' do
+  subject { object.generate { node } }
+
+  class Block
+    attr_reader :arguments
+
+    def called?
+      defined?(@arguments)
+    end
+
+    def call(*arguments)
+      @arguments = arguments
+    end
+  end
+
+  let(:object)       { described_class.new(wrapped_node,block) }
+  let(:block)        { Block.new                               }
+  let(:wrapped_node) { '"foo"'.to_ast                          }
+
+  context 'when new AST is generated' do
+    let(:node) { '"bar"'.to_ast }
+
+    it 'should call block' do
+      subject
+      block.should be_called
+    end
+
+    it 'should call block with node' do
+      subject
+      block.arguments.should eql([node])
+    end
+  end
+  
+  context 'when new AST could not be generated' do
+    let(:node) { '"foo"'.to_ast }
+
+    it 'should raise error' do
+      expect { subject }.to raise_error(RuntimeError,'New AST could not be generated after 3 attempts')
+    end
+  end
+end