Add rescue/else-body promotion/concatenation mutation

[fix #245]

Changelog.md

@@ -1,3 +1,7 @@
+# v0.6.1 2014-08-16
+
+* Add rescue else body promotion/concatenation mutation
+
 # v0.6.0 2014-08-11
 
 * Parallel execution / reporting.

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 1069
+total_score: 1076

config/reek.yml

@@ -37,6 +37,7 @@ FeatureEnvy:
   - Mutant::Matcher::Method::Singleton#receiver?
   - Mutant::Mutation::Evil#success?
   - Mutant::Mutation::Neutral#success?
+  - Mutant::Mutator::Node#children_indices
   # False positive, its a utility
   - Mutant::Meta::Example::Verification#format_mutation
   - Mutant::Reporter::CLI#subject_results

lib/mutant/mutator/node.rb

@@ -8,6 +8,8 @@ module Mutant
       include AbstractType, Unparser::Constants
       include AST::NamedChildren, AST::NodePredicates, AST::Sexp, AST::Nodes
 
+      TAUTOLOGY = ->(_input) { true }
+
       # Helper to define a named child
       #
       # @param [Parser::AST::Node] node
@@ -79,7 +81,7 @@ module Mutant
       # @api private
       #
       def mutate_child(index, mutator = Mutator, &block)
-        block ||= ->(_node) { true }
+        block ||= TAUTOLOGY
         child = children.at(index)
         mutator.each(child, self) do |mutation|
           next unless block.call(mutation)
@@ -211,6 +213,20 @@ module Mutant
         AST::Types::OP_ASSIGN.include?(parent_type) && parent.node.children.first.equal?(node)
       end
 
+      # Return children indices
+      #
+      # @param [Range] range
+      #
+      # @return [Enumerable<Fixnum>]
+      #
+      # @api pirvate
+      #
+      def children_indices(range)
+        range_end = range.end
+        last_index = range_end >= 0 ? range_end : children.length + range_end
+        range.begin.upto(last_index)
+      end
+
     end # Node
   end # Mutator
 end # Mutant

lib/mutant/mutator/node/rescue.rb

@@ -2,10 +2,80 @@ module Mutant
   class Mutator
     class Node
       # Mutator for rescue nodes
-      class Rescue < Generic
+      class Rescue < self
 
         handle :rescue
 
+        children :body
+
+        define_named_child(:else_body, -1)
+
+        RESCUE_INDICES = (1..-2).freeze
+
+        # Emit mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def dispatch
+          mutate_body
+          mutate_rescue_bodies
+          mutate_else_body
+        end
+
+      private
+
+        # Mutate child by name
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def mutate_rescue_bodies
+          children_indices(RESCUE_INDICES).each do |index|
+            next unless children.at(index)
+            mutate_child(index)
+          end
+        end
+
+        # Emit concatenation with body
+        #
+        # @param [Parser::AST::Node] child
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def emit_concat(child)
+          raise unless body
+          emit(s(:begin, body, child))
+        end
+
+        # Emit body mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def mutate_body
+          return unless body
+          emit_body_mutations
+          emit(body)
+        end
+
+        # Emit else body mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def mutate_else_body
+          return unless else_body
+          emit_else_body_mutations
+          emit_concat(else_body)
+        end
+
       end # Rescue
     end # Node
   end # Mutator

lib/mutant/mutator/node/send/index.rb

@@ -35,7 +35,7 @@ module Mutant
             # @api private
             #
             def mutate_indices
-              INDEX_RANGE.begin.upto(children.length + INDEX_RANGE.end).each do |index|
+              children_indices(INDEX_RANGE).each do |index|
                 delete_child(index)
                 mutate_child(index)
               end

meta/def.rb

@@ -13,6 +13,33 @@ Mutant::Meta::Example.add do
   mutation 'def foo; nil; rescue; end'
   mutation 'def foo; self; rescue; end'
   mutation 'def foo; end'
+
+  # Promote rescue body
+  mutation 'def foo; foo; end'
+end
+
+Mutant::Meta::Example.add do
+  source 'def a; foo; rescue; bar; else; baz; end'
+
+  # Mutate all bodies
+  mutation 'def a; nil;  rescue; bar; else; baz; end'
+  mutation 'def a; self; rescue; bar; else; baz; end'
+  mutation 'def a; foo; rescue; nil;  else; baz; end'
+  mutation 'def a; foo; rescue; self; else; baz; end'
+  mutation 'def a; foo; rescue; bar; else; nil; end'
+  mutation 'def a; foo; rescue; bar; else; self; end'
+
+  # Promote and concat else body
+  mutation 'def a; foo; baz; end'
+
+  # Promote body
+  mutation 'def a; foo; end'
+
+  # Empty body
+  mutation 'def a; end'
+
+  # Failing body
+  mutation 'def a; raise; end'
 end
 
 Mutant::Meta::Example.add do