From da5b844c63f6f4b29a9f6921fc3256c2674d677a Mon Sep 17 00:00:00 2001
From: "adam.hutchison" <liveh2o@gmail.com>
Date: Fri, 9 Nov 2018 12:52:02 -0700
Subject: [PATCH] Fix enum hash equality

Protobuf::Enum delegates methods to Fixnum, which has a custom hash
equality method (`eql?`). This causes enum values to be equivalent when
using `==`, `===`, `equals?`, but not `eql?`**:

2.3.7 :002 > Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO)
 => false

However, they are equilvalent to their tag value:

2.3.7 :002 > Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO.tag)
 => true

Use the hash equality implementation from Object#eql?, which is
equivalent to == instead.

**The implementation changed in Ruby 2.5, so this only affects Ruby
versions less than v2.5.
---
 lib/protobuf/enum.rb           | 19 +++++++++++++++++++
 spec/lib/protobuf/enum_spec.rb | 14 ++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/lib/protobuf/enum.rb b/lib/protobuf/enum.rb
index a50ebc54..f9d5d4de 100644
--- a/lib/protobuf/enum.rb
+++ b/lib/protobuf/enum.rb
@@ -271,6 +271,25 @@ def class
       tag.class
     end
 
+    # Protobuf::Enum delegates methods to Fixnum, which has a custom hash equality method (`eql?`)
+    # This causes enum values to be equivalent when using `==`, `===`, `equals?`, but not `eql?`**:
+    #
+    #   2.3.7 :002 > ::Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO)
+    #    => false
+    #
+    # However, they are equilvalent to their tag value:
+    #
+    #   2.3.7 :002 > ::Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO.tag)
+    #    => true
+    #
+    # **The implementation changed in Ruby 2.5, so this only affects Ruby versions less than v2.4.
+    #
+    # Use the hash equality implementation from Object#eql?, which is equivalent to == instead.
+    #
+    def eql?(other)
+      self == other
+    end
+
     def inspect
       "\#<Protobuf::Enum(#{parent_class})::#{name}=#{tag}>"
     end
diff --git a/spec/lib/protobuf/enum_spec.rb b/spec/lib/protobuf/enum_spec.rb
index a2bebb8d..49b9602b 100644
--- a/spec/lib/protobuf/enum_spec.rb
+++ b/spec/lib/protobuf/enum_spec.rb
@@ -268,6 +268,20 @@
     specify { subject.try { |yielded| expect(yielded).to eq(subject) } }
   end
 
+  describe '#eql?' do
+    it "is equal to itself" do
+      expect(::Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO)).to be(true)
+    end
+
+    it "is equal to it's tag" do
+      expect(::Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO.tag)).to be(true)
+    end
+
+    it "is not equal to it's name" do
+      expect(::Test::EnumTestType::ZERO.eql?(::Test::EnumTestType::ZERO.name)).to be(false)
+    end
+  end
+
   context 'when coercing from enum' do
     subject { Test::StatusType::PENDING }
     it { is_expected.to eq(0) }