Improve AST coverage of mutant

* Uses a monkeypach extension to parser with a list of valid node types.
* Add nodes, found to be uncovered to generic mutator.

Gemfile

@@ -2,6 +2,8 @@
 
 source 'https://rubygems.org'
 
+gem 'unparser', git: 'https://github.com/mbj/unparser'
+
 gemspec
 
 gem 'mutant', path: '.'

lib/mutant.rb

@@ -22,6 +22,30 @@ require 'anima'
 require 'concord'
 require 'rspec'
 
+# Monkeypatch on parser with a list of allowed nodes.
+# Will be pushed upstream once turning out to be correct.
+module Parser
+  module Meta
+    NODE_TYPES =
+      %w(
+        true false nil int float str dstr str
+        sym dsym xstr regopt regexp array splat
+        array pair kwsplat hash irange erange self
+        lvar ivar cvar gvar const defined? lvasgn
+        ivasgn cvasgn gvasgn casgn mlhs masgn op_asgn
+        op_asgn and_asgn ensure rescue arg_expr
+        or_asgn and_asgn or_asgn back_ref nth_ref
+        match_with_lvasgn match_current_line
+        module class sclass def defs undef alias args
+        cbase arg optarg restarg blockarg block_pass args def kwarg kwoptarg
+        kwrestarg send super zsuper yield block send
+        and not or if when case while until while_post
+        until_post for break next redo return resbody
+        kwbegin begin retry preexe postexe iflipflop eflipflop
+      ).map(&:to_sym).to_set.freeze
+  end # Meta
+end # Parser
+
 # Library namespace
 module Mutant
   # The empty string used within this namespace
@@ -139,3 +163,4 @@ require 'mutant/reporter/cli/printer/subject'
 require 'mutant/reporter/cli/printer/killer'
 require 'mutant/reporter/cli/printer/mutation'
 require 'mutant/zombifier'
+

lib/mutant/constants.rb

@@ -35,25 +35,19 @@ module Mutant
     METHOD_OPERATORS + INDEX_OPERATORS + UNARY_METHOD_OPERATORS
   ).to_set.freeze
 
-  # Hopefully all node types parser does generate.
+  # Nodes that are NOT handled by mutant.
   #
-  # FIXME: Maintain this list only in unparser / parser!
+  # not - 1.8 only, mutant does not support 1.8
   #
-  NODE_TYPES = [
-    :lvasgn, :ivasgn, :cvasgn, :gvasgn,
-    :casgn, :masgn, :mlhs, :break, :rescue,
-    :ensure, :resbody, :begin, :retry, :arg_expr,
-    :args, :blockarg, :optarg, :kwrestarg, :kwoptarg,
-    :kwarg, :restarg, :arg, :block_pass, :or, :and,
-    :next, :undef, :if, :module, :cbase, :block, :send,
-    :zsuper, :super, :empty, :alias, :for, :redo,
-    :return, :splat, :defined?, :op_asgn, :self,
-    :true, :false, :nil, :dstr, :dsym, :regexp,
-    :regopt, :int, :str, :float, :sym, :pair, :hash, :array,
-    :xstr, :def, :defs, :case, :when, :ivar, :lvar, :cvar, :gvar,
-    :back_ref, :const, :nth_ref, :class, :sclass, :yield,
-    :match_with_lvasgn, :match_current_line, :irange, :erange,
-    :or_asgn, :kwbegin, :and_asgn, :while
-  ].to_set.freeze
+  NODE_BLACKLIST = %w(
+    not
+  ).map(&:to_sym).freeze
+
+  # Nodes that are NOT generated by parser but used by mutant / unparser.
+  NODE_EXTRA = %w(
+    empty
+  ).map(&:to_sym).freeze
+
+  NODE_TYPES = ((Parser::Meta::NODE_TYPES + NODE_EXTRA) - NODE_BLACKLIST).to_set.freeze
 
 end # Mutant

lib/mutant/node_helpers.rb

@@ -13,7 +13,7 @@ module Mutant
     # @api private
     #
     def s(type, *children)
-      Parser::AST::Node.new(type, children)
+      ::Parser::AST::Node.new(type, children)
     end
     module_function :s
 

spec/integration/mutant/test_mutator_handles_types_spec.rb

@@ -3,6 +3,7 @@
 require 'spec_helper'
 
 describe Mutant do
+
   specify 'mutant should not crash for any node parser can generate' do
     Mutant::NODE_TYPES.each do |type|
       Mutant::Mutator::Registry.lookup(Mutant::NodeHelpers.s(type))