From 8cf5e0f079002ce7bd838817c207e9bc8ca32932 Mon Sep 17 00:00:00 2001
From: Markus Schirp <mbj@schirp-dso.com>
Date: Mon, 24 Dec 2018 15:41:15 +0000
Subject: [PATCH] Change to skip regexp bodies regexp_parser does not accept

[Fix #813]
---
 lib/mutant/ast/regexp.rb                  |  7 ++++++-
 lib/mutant/mutator/node/literal/regex.rb  |  8 ++++----
 meta/regexp.rb                            |  9 +++++++++
 spec/integrations.yml                     | 10 +---------
 spec/unit/mutant/ast/regexp/parse_spec.rb | 16 ++++++++++++++--
 5 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/lib/mutant/ast/regexp.rb b/lib/mutant/ast/regexp.rb
index eee61cfc..39a8aa67 100644
--- a/lib/mutant/ast/regexp.rb
+++ b/lib/mutant/ast/regexp.rb
@@ -8,10 +8,15 @@ module Mutant
       #
       # @param regexp [String]
       #
-      # @return [Regexp::Expression]
+      # @return [Regexp::Expression, nil]
+      #
+      # rubocop:disable Lint/HandleExceptions
       def self.parse(regexp)
         ::Regexp::Parser.parse(regexp)
+      # regexp_parser is more strict than MRI
+      rescue ::Regexp::Scanner::PrematureEndError
       end
+      # rubocop:enable Lint/HandleExceptions
 
       # Convert expression into ast node
       #
diff --git a/lib/mutant/mutator/node/literal/regex.rb b/lib/mutant/mutator/node/literal/regex.rb
index 39d779ea..5d0e4e9a 100644
--- a/lib/mutant/mutator/node/literal/regex.rb
+++ b/lib/mutant/mutator/node/literal/regex.rb
@@ -42,7 +42,7 @@ module Mutant
           #
           # @return [undefined]
           def mutate_body
-            return unless body.all?(&method(:n_str?))
+            return unless body.all?(&method(:n_str?)) && body_ast
 
             Mutator.mutate(body_ast).each do |mutation|
               source = AST::Regexp.to_expression(mutation).to_s
@@ -52,14 +52,14 @@ module Mutant
 
           # AST representation of regexp body
           #
-          # @return [Parser::AST::Node]
+          # @return [Parser::AST::Node, nil]
           def body_ast
-            AST::Regexp.to_ast(body_expression)
+            body_expression and AST::Regexp.to_ast(body_expression)
           end
 
           # Expression representation of regexp body
           #
-          # @return [Regexp::Expression]
+          # @return [Regexp::Expression, nil]
           def body_expression
             AST::Regexp.parse(body.map(&:children).join)
           end
diff --git a/meta/regexp.rb b/meta/regexp.rb
index 8952a5a1..ca127f03 100644
--- a/meta/regexp.rb
+++ b/meta/regexp.rb
@@ -76,6 +76,15 @@ Mutant::Meta::Example.add :regexp do
   mutation '/(?(1)(foo)(?:bar))/'
 end
 
+# Case where MRI would accept an expression but regexp_parser not.
+Mutant::Meta::Example.add :regexp do
+  source '/u{/'
+
+  singleton_mutations
+  mutation '//'
+  mutation '/nomatch\A/'
+end
+
 Pathname
   .glob(Pathname.new(__dir__).join('regexp', '*.rb'))
   .sort
diff --git a/spec/integrations.yml b/spec/integrations.yml
index 1f5dac3d..0b260fca 100644
--- a/spec/integrations.yml
+++ b/spec/integrations.yml
@@ -7,15 +7,7 @@
   ruby_glob_pattern: '**/*_spec.rb'
   mutation_coverage: false
   mutation_generation: true
-  expected_errors:
-    "#<Parser::SyntaxError: invalid multibyte escape: /\xAA/>":
-      - language/regexp/escapes_spec.rb
-    '#<RegexpError: invalid multibyte escape: /\xAA/>':
-      - language/regexp/escapes_spec.rb
-    "#<Regexp::Scanner::PrematureEndError: Premature end of pattern at #{str}>":
-      - language/regexp/interpolation_spec.rb
-    '#<Regexp::Scanner::PrematureEndError: Premature end of pattern at \xA>':
-      - language/regexp/escapes_spec.rb
+  expected_errors: {}
   exclude:
     - core/string/casecmp_spec.rb
     - core/symbol/casecmp_spec.rb
diff --git a/spec/unit/mutant/ast/regexp/parse_spec.rb b/spec/unit/mutant/ast/regexp/parse_spec.rb
index 3094b64e..b0062cd4 100644
--- a/spec/unit/mutant/ast/regexp/parse_spec.rb
+++ b/spec/unit/mutant/ast/regexp/parse_spec.rb
@@ -1,7 +1,19 @@
 # frozen_string_literal: true
 
 RSpec.describe Mutant::AST::Regexp, '.parse' do
-  it 'parses using minor ruby version' do
-    expect(described_class.parse(/foo/).to_re).to eql(/foo/)
+  def apply(input)
+    described_class.parse(input)
+  end
+
+  context 'on regexp regexp_parser does accept' do
+    it 'parses using minor ruby version' do
+      expect(apply(/foo/).to_re).to eql(/foo/)
+    end
+  end
+
+  context 'on regexp regexp_parser does not accept' do
+    it 'returns nil' do
+      expect(apply(/u{/)).to be(nil)
+    end
   end
 end