From cfbe4f1d48ad5b6004bbaae5ea923aa6f74dd06b Mon Sep 17 00:00:00 2001
From: Daniel Gollahon <daniel.gollahon@gmail.com>
Date: Sat, 2 Jan 2021 20:08:15 -0800
Subject: [PATCH] Add `/static\z/` -> `#end_with?` mutations

- Adds the following mutations:
  * `a.match(/text\z/)` -> `b.end_with?('text')`
  * `a.match?(/text\z/)` -> `b.end_with?('text')`
  * `a =~ /text\z/` -> `b.end_with?('text')`
---
 Changelog.md                    |  4 ++++
 lib/mutant/mutator/node/send.rb | 15 ++++++++++-----
 meta/send.rb                    | 15 +++++++++++++++
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index 4b7914520..f0c69a11f 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -6,6 +6,10 @@
       * `a.match(/\Atext/)` -> `b.start_with?('text')`
       * `a.match?(/\Atext/)` -> `b.start_with?('text')`
       * `a =~ /\Atext/` -> `b.start_with?('text')`
+    * Add `/static\z/` -> `#end_with?` mutations:
+      * `a.match(/text\z/)` -> `b.end_with?('text')`
+      * `a.match?(/text\z/)` -> `b.end_with?('text')`
+      * `a =~ /text\z/` -> `b.end_with?('text')`
 
 # v0.10.25 2021-01-02-03
 
diff --git a/lib/mutant/mutator/node/send.rb b/lib/mutant/mutator/node/send.rb
index 9945412e7..cb8991bd6 100644
--- a/lib/mutant/mutator/node/send.rb
+++ b/lib/mutant/mutator/node/send.rb
@@ -107,11 +107,16 @@ def emit_start_with_mutation
             regexp_ast = AST::Regexp.expand_regexp_ast(argument)
           )
 
-          return unless regexp_ast.children.map(&:type).eql?(%i[regexp_bos_anchor regexp_literal_literal])
-
-          literal = Mutant::Util.one(regexp_ast.children.last.children)
-
-          emit(s(:send, receiver, :start_with?, s(:str, literal)))
+          regexp_children   = regexp_ast.children
+          regexp_node_types = regexp_children.map(&:type)
+
+          if regexp_node_types.eql?(%i[regexp_bos_anchor regexp_literal_literal])
+            literal = Mutant::Util.one(regexp_children.last.children)
+            emit(s(:send, receiver, :start_with?, s(:str, literal)))
+          elsif regexp_node_types.eql?(%i[regexp_literal_literal regexp_eos_anchor])
+            literal = Mutant::Util.one(regexp_children.first.children)
+            emit(s(:send, receiver, :end_with?, s(:str, literal)))
+          end
         end
 
         def emit_predicate_mutations
diff --git a/meta/send.rb b/meta/send.rb
index 79c48d663..ddf530e42 100644
--- a/meta/send.rb
+++ b/meta/send.rb
@@ -811,3 +811,18 @@
   mutation 'foo(//)'
   mutation 'foo(/nomatch\A/)'
 end
+
+Mutant::Meta::Example.add :send do
+  source 'a.match(/foo\z/)'
+
+  singleton_mutations
+
+  mutation 'a.match?(/foo\z/)'
+  mutation 'a.match'
+  mutation 'a'
+  mutation '/foo\z/'
+  mutation 'a.match(//)'
+  mutation 'a.match(/nomatch\A/)'
+  mutation 'self.match(/foo\z/)'
+  mutation "a.end_with?('foo')"
+end