Fix constant scope of inserted mutations

[Fix #1422]

Changelog.md

@@ -1,4 +1,8 @@
-# v0.11.29 [unreleased]
+# v0.11.29 2024-03-09
+
+* [#1426](https://github.com/mbj/mutant/pull/1426)
+  Fix mutations to unintentionally change constant scope.
+  This fixes: https://github.com/mbj/mutant/issues/1422.
 
 * [#1421](https://github.com/mbj/mutant/pull/1421)
   Change to optional warning display via --print-warnings environment option.

lib/mutant/ast.rb

@@ -8,12 +8,12 @@ class AST
     )
 
     class View
-      include Adamantium, Anima.new(:node, :path)
+      include Adamantium, Anima.new(:node, :stack)
     end
 
     def on_line(line)
-      line_map.fetch(line, EMPTY_HASH).map do |node, path|
-        View.new(node: node, path: path)
+      line_map.fetch(line, EMPTY_HASH).map do |node, stack|
+        View.new(node: node, stack: stack)
       end
     end
 
@@ -22,21 +22,20 @@ def on_line(line)
     def line_map
       line_map = {}
 
-      walk_path(node) do |node, path|
+      walk_path(node, []) do |node, stack|
         expression = node.location.expression || next
-        (line_map[expression.line] ||= []) << [node, path]
+        (line_map[expression.line] ||= []) << [node, stack]
       end
 
       line_map
     end
     memoize :line_map
 
-    def walk_path(node, stack = [node.type], &block)
-      block.call(node, stack.dup)
+    def walk_path(node, stack, &block)
+      block.call(node, stack)
+      stack = [*stack, node]
       node.children.grep(::Parser::AST::Node) do |child|
-        stack.push(child.type)
         walk_path(child, stack, &block)
-        stack.pop
       end
     end
   end # AST

lib/mutant/context.rb

@@ -3,38 +3,53 @@
 module Mutant
   # An abstract context where mutations can be applied to.
   class Context
-    include Adamantium, Anima.new(:scope, :source_path)
-    extend AST::Sexp
+    include Adamantium, Anima.new(:constant_scope, :scope, :source_path)
 
-    def match_expressions
-      scope.match_expressions
+    class ConstantScope
+      include AST::Sexp
+
+      class Class < self
+        include Anima.new(:const, :descendant)
+
+        def call(node)
+          s(:class, const, nil, descendant.call(node))
+        end
+      end
+
+      class Module < self
+        include Anima.new(:const, :descendant)
+
+        def call(node)
+          s(:module, const, descendant.call(node))
+        end
+      end
+
+      class None < self
+        include Equalizer.new
+
+        def call(node)
+          node
+        end
+      end
     end
 
-    # Identification string
-    #
-    # @return [String]
-    def identification
-      scope.raw.name
+    def match_expressions
+      scope.match_expressions
     end
 
     # Return root node for mutation
     #
     # @return [Parser::AST::Node]
     def root(node)
-      scope.nesting.reverse.reduce(node) do |current, raw_scope|
-        self.class.wrap(raw_scope, current)
-      end
+      constant_scope.call(node)
     end
 
-    # Wrap node into ast node
-    def self.wrap(raw_scope, node)
-      name = s(:const, nil, raw_scope.name.split(Scope::NAMESPACE_DELIMITER).last.to_sym)
-      case raw_scope
-      when Class
-        s(:class, name, nil, node)
-      when Module
-        s(:module, name, node)
-      end
+    # Identification string
+    #
+    # @return [String]
+    def identification
+      scope.raw.name
     end
+
   end # Context
 end # Mutant

lib/mutant/matcher/method.rb

@@ -14,6 +14,11 @@ class Method < self
       CLOSURE_WARNING_FORMAT =
         '%s is dynamically defined in a closure, unable to emit subject'
 
+      CONSTANT_SCOPES = {
+        class:  Context::ConstantScope::Class,
+        module: Context::ConstantScope::Module
+      }.freeze
+
       # Matched subjects
       #
       # @param [Env] env
@@ -28,6 +33,8 @@ def call(env)
       # Present to avoid passing the env argument around in case the
       # logic would be implemented directly on the Matcher::Method
       # instance
+      #
+      # rubocop:disable Metrics/ClassLength
       class Evaluator
         include(
           AbstractType,
@@ -57,7 +64,7 @@ def call
         def match_view
           return EMPTY_ARRAY if matched_view.nil?
 
-          if matched_view.path.any?(&:block.public_method(:equal?))
+          if matched_view.stack.any? { |node| node.type.equal?(:block) }
             env.warn(CLOSURE_WARNING_FORMAT % target_method)
 
             return EMPTY_ARRAY
@@ -80,7 +87,26 @@ def method_name
         end
 
         def context
-          Context.new(scope: scope, source_path: source_path)
+          Context.new(constant_scope: constant_scope, scope: scope, source_path: source_path)
+        end
+
+        # rubocop:disable Metrics/MethodLength
+        def constant_scope
+          matched_view
+            .stack
+            .reverse
+            .reduce(Context::ConstantScope::None.new) do |descendant, node|
+              klass = CONSTANT_SCOPES[node.type]
+
+              if klass
+                klass.new(
+                  const:      node.children.fetch(0),
+                  descendant: descendant
+                )
+              else
+                descendant
+              end
+          end
         end
 
         def ast

lib/mutant/meta/example.rb

@@ -39,8 +39,9 @@ def identification
       # @return [Context]
       def context
         Context.new(
-          scope:       scope,
-          source_path: location.path
+          constant_scope: Context::ConstantScope::None.new,
+          scope:          scope,
+          source_path:    location.path
         )
       end
 

spec/support/shared_context.rb

@@ -128,8 +128,9 @@ def setup_shared_context
 
     let(:subject_a_context) do
       Mutant::Context.new(
-        scope:       scope,
-        source_path: 'suvject-a.rb'
+        constant_scope: Mutant::Context::ConstantScope::None.new,
+        scope:          scope,
+        source_path:    'subject-a.rb'
       )
     end
 

spec/unit/mutant/ast_spec.rb

@@ -11,8 +11,10 @@ def apply(line)
     let(:node) do
       Unparser.parse(<<~RUBY)
 
-        begin
-          1; 2
+        def foo
+          begin
+            1; 2
+          end
         end
       RUBY
     end
@@ -27,18 +29,18 @@ def apply(line)
       it 'returns expected view' do
         expect(apply(2)).to eql(
           [
-            described_class::View.new(node: node, path: %i[kwbegin])
+            described_class::View.new(node: node, stack: [])
           ]
         )
       end
     end
 
     context 'line populated with more than one' do
       it 'returns expected view' do
-        expect(apply(3)).to eql(
+        expect(apply(4)).to eql(
           [
-            described_class::View.new(node: s(:int, 1), path: %i[kwbegin int]),
-            described_class::View.new(node: s(:int, 2), path: %i[kwbegin int])
+            described_class::View.new(node: s(:int, 1), stack: [node, node.children.fetch(2)]),
+            described_class::View.new(node: s(:int, 2), stack: [node, node.children.fetch(2)])
           ]
         )
       end

spec/unit/mutant/cli_spec.rb

@@ -746,10 +746,14 @@ def self.main_body
         )
       end
 
+      let(:constant_scope) do
+        Mutant::Context::ConstantScope::None.new
+      end
+
       let(:subject_a) do
         Mutant::Subject::Method::Instance.new(
           config:     Mutant::Subject::Config::DEFAULT,
-          context:    Mutant::Context.new(scope: scope, source_path: 'subject.rb'),
+          context:    Mutant::Context.new(constant_scope: constant_scope, scope: scope, source_path: 'subject.rb'),
           node:       s(:def, :send, s(:args), nil),
           visibility: :public
         )