[ruby/did_you_mean] Do not suggest #name= for #name and vice versa

(https://github.com/ruby/did_you_mean/pull/180)

* Do not suggest #name= for #name and vice versa
* Avoid allocating unnecessary MatchData

Co-authored-by: Jean byroot Boussier <jean.boussier+github@shopify.com>
Co-authored-by: Jean byroot Boussier <jean.boussier+github@shopify.com>

lib/did_you_mean/spell_checkers/method_name_checker.rb

@@ -59,6 +59,13 @@ module DidYouMean
         method_names = receiver.methods + receiver.singleton_methods
         method_names += receiver.private_methods if @private_call
         method_names.uniq!
+        # Assume that people trying to use a writer are not interested in a reader
+        # and vice versa
+        if method_name.match?(/=\Z/)
+          method_names.select! { |name| name.match?(/=\Z/) }
+        else
+          method_names.reject! { |name| name.match?(/=\Z/) }
+        end
         method_names
       else
         []

test/did_you_mean/spell_checking/test_method_name_check.rb

@@ -4,6 +4,8 @@ class MethodNameCheckTest < Test::Unit::TestCase
   include DidYouMean::TestHelper
 
   class User
+    attr_writer :writer
+    attr_reader :reader
     def friends; end
     def first_name; end
     def descendants; end
@@ -144,4 +146,20 @@ class MethodNameCheckTest < Test::Unit::TestCase
     assert_correction [], error.corrections
     assert_not_match(/Did you mean\? +yield/, get_message(error))
   end if RUBY_ENGINE != "jruby"
+
+  # Do not suggest `name=` for `name`
+  def test_does_not_suggest_writer
+    error = assert_raise(NoMethodError) { @user.writer }
+
+    assert_correction [], error.corrections
+    assert_not_match(/Did you mean\?  writer=/, get_message(error))
+  end
+
+  # Do not suggest `name` for `name=`
+  def test_does_not_suggest_reader
+    error = assert_raise(NoMethodError) { @user.reader = 1 }
+
+    assert_correction [], error.corrections
+    assert_not_match(/Did you mean\?  reader/, get_message(error))
+  end
 end