Reduce and specify behavior of matcher compiler

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 1045
+total_score: 1053

lib/mutant/expression.rb

@@ -17,7 +17,10 @@ module Mutant
 
     REGISTRY = {}
 
+    # Error raised on invalid expressions
     class InvalidExpressionError < RuntimeError; end
+
+    # Error raised on ambigous expressions
     class AmbigousExpressionError < RuntimeError; end
 
     # Initialize expression

lib/mutant/matcher/chain.rb

@@ -24,22 +24,6 @@ module Mutant
         self
       end
 
-      # Build matcher chain
-      #
-      # @param [Enumerable<Matcher>] matchers
-      #
-      # @return [Matcher]
-      #
-      # @api private
-      #
-      def self.build(matchers)
-        if matchers.length.equal?(1)
-          return matchers.first
-        end
-
-        new(matchers)
-      end
-
     end # Chain
   end # Matcher
 end # Mutant

lib/mutant/matcher/compiler.rb

@@ -12,23 +12,51 @@ module Mutant
       # @api private
       #
       def result
-        matchers = config.match_expressions.map(&method(:matcher))
-
-        if matchers.empty?
-          return Matcher::Null.new
-        end
-
-        matcher = Matcher::Chain.build(matchers)
-
-        if predicate
-          Matcher::Filter.new(matcher, predicate)
-        else
-          matcher
-        end
+        Filter.new(
+          Chain.build(config.match_expressions.map(&method(:matcher))),
+          predicate
+        )
       end
 
+      # Subject expression prefix predicate
+      class SubjectPrefix
+        include Concord.new(:expression)
+
+        # Test if subject expression is matched by prefix
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def call(subject)
+          expression.prefix?(subject.expression)
+        end
+
+      end # SubjectPrefix
+
     private
 
+      # Return predicate
+      #
+      # @return [#call]
+      #
+      # @api private
+      #
+      def predicate
+        if subject_selector && subject_rejector
+          Morpher::Evaluator::Predicate::Boolean::And.new([
+            subject_selector,
+            Morpher::Evaluator::Predicate::Negation.new(subject_rejector)
+          ])
+        elsif subject_selector
+          subject_selector
+        elsif subject_rejector
+          Morpher::Evaluator::Predicate::Negation.new(subject_rejector)
+        else
+          Morpher::Evaluator::Predicate::Tautology.new
+        end
+      end
+
       # Return subject selector
       #
       # @return [#call]
@@ -47,31 +75,6 @@ module Mutant
         Morpher::Evaluator::Predicate::Boolean::Or.new(selectors) if selectors.any?
       end
 
-      # Return predicate
-      #
-      # @return [#call]
-      #   if filter is needed
-      #
-      # @return [nil]
-      #   othrwise
-      #
-      # @api private
-      #
-      def predicate
-        if subject_selector && subject_rejector
-          Morpher::Evaluator::Predicate::Boolean::And.new([
-            subject_selector,
-            Morpher::Evaluator::Predicate::Negation.new(subject_rejector)
-          ])
-        elsif subject_selector
-          subject_selector
-        elsif subject_rejector
-          Morpher::Evaluator::Predicate::Negation.new(subject_rejector)
-        else
-          nil
-        end
-      end
-
       # Return subject rejector
       #
       # @return [#call]
@@ -83,9 +86,7 @@ module Mutant
       # @api private
       #
       def subject_rejector
-        rejectors = config.subject_ignores.map(&method(:matcher)).flat_map(&:to_a).map do |subject|
-          Morpher.compile(s(:eql, s(:attribute, :identification), s(:static, subject.identification)))
-        end
+        rejectors = config.subject_ignores.map(&SubjectPrefix.method(:new))
 
         Morpher::Evaluator::Predicate::Boolean::Or.new(rejectors) if rejectors.any?
       end

lib/mutant/matcher/null.rb

@@ -2,7 +2,7 @@ module Mutant
   class Matcher
     # A null matcher, that does not match any subjects
     class Null < self
-      include Equalizer.new
+      include Concord.new
 
       # Enumerate subjects
       #

spec/unit/mutant/matcher/chain_spec.rb

@@ -42,19 +42,4 @@ describe Mutant::Matcher::Chain do
 
     it_should_behave_like 'an idempotent method'
   end
-
-  describe '.build' do
-    subject { described_class.build(matchers) }
-
-    context 'when one matcher given' do
-      let(:matchers) { [double('Matcher A')] }
-      it { should be(matchers.first) }
-    end
-
-    context 'when matchers given' do
-      let(:matchers) { [double('Matcher A'), double('Matcher B')] }
-      it { should eql(described_class.new(matchers)) }
-    end
-  end
-
 end

spec/unit/mutant/matcher/compiler_spec.rb

@@ -0,0 +1,96 @@
+require 'spec_helper'
+
+describe Mutant::Matcher::Compiler do
+  let(:object) { described_class }
+
+  let(:env) { Fixtures::TEST_ENV }
+
+  let(:expression_a) { Mutant::Expression.parse('Foo*') }
+  let(:expression_b) { Mutant::Expression.parse('Bar*') }
+
+  let(:matcher_a) { expression_a.matcher(env) }
+  let(:matcher_b) { expression_b.matcher(env) }
+
+  let(:expected_matcher) do
+    Mutant::Matcher::Filter.new(expected_positive_matcher, expected_predicate)
+  end
+
+  let(:expected_predicate) do
+    Morpher.compile(s(:true))
+  end
+
+  describe '.call' do
+    subject { object.call(env, matcher_config.update(attributes)) }
+
+    let(:matcher_config) { Mutant::Matcher::Config::DEFAULT }
+
+
+    context 'on empty config' do
+      let(:attributes) { {} }
+
+      let(:expected_positive_matcher) { Mutant::Matcher::Chain.new([]) }
+
+      it { should eql(expected_matcher) }
+    end
+
+    context 'on config with match expression' do
+      context 'and no filter' do
+        let(:attributes) do
+          { match_expressions: [expression_a] }
+        end
+
+        let(:expected_positive_matcher) { Mutant::Matcher::Chain.new([matcher_a]) }
+
+        it { should eql(expected_matcher) }
+      end
+
+      context 'and a subject filter' do
+        let(:attributes) do
+          {
+            match_expressions: [expression_a],
+            subject_ignores:   [expression_b]
+          }
+        end
+
+        let(:expected_positive_matcher) { Mutant::Matcher::Chain.new([matcher_a]) }
+
+        let(:expected_predicate) {
+          Morpher::Evaluator::Predicate::Negation.new(
+            Morpher::Evaluator::Predicate::Boolean::Or.new([
+              described_class::SubjectPrefix.new(expression_b)
+            ])
+          )
+        }
+
+        it { should eql(expected_matcher) }
+      end
+
+      context 'and an attribute filter' do
+        let(:attributes) do
+          {
+            match_expressions: [expression_a],
+            subject_selects:   [[:code, 'foo']]
+          }
+        end
+
+        let(:expected_positive_matcher) { Mutant::Matcher::Chain.new([matcher_a]) }
+
+        let(:expected_predicate) {
+          Morpher::Evaluator::Predicate::Boolean::Or.new([
+            Morpher.compile(s(:eql, s(:attribute, :code), s(:static, 'foo')))
+          ])
+        }
+
+        it { should eql(expected_matcher) }
+      end
+    end
+
+    context 'on config with multiple match expressions' do
+      let(:attributes) do
+        { match_expressions: [expression_a, expression_b] }
+      end
+
+      let(:expected_positive_matcher) { Mutant::Matcher::Chain.new([matcher_a, matcher_b]) }
+    end
+  end
+end