Array#uniq does not remove equal Twingly::URLs

[walro]

[2] pry(main)> url = "https://www.twingly.com"
=> "https://www.twingly.com"
[3] pry(main)> Twingly::URL.parse(url) == Twingly::URL.parse(url)
=> true
[4] pry(main)> [Twingly::URL.parse(url), Twingly::URL.parse(url)].uniq.size
=> 2

In the sample above I would expect to get 1 element back.

[dentarg]

Great catch, not sure how we can solve it (seems tricky)

I will dump the workaround you used here:

$ irb -rtwingly/url
irb(main):001:0> a = Twingly::URL.parse("http://google.com")
=> #<Twingly::URL:0x3fc7cf08b444 http://google.com>
irb(main):002:0> b = Twingly::URL.parse("http://google.com")
=> #<Twingly::URL:0x3fc7cec9e890 http://google.com>
irb(main):003:0> [a, b].uniq(&:to_s)
=> [#<Twingly::URL:0x3fc7cf08b444 http://google.com>]

[jage]

I think this is how to solve it.

diff --git a/lib/twingly/url.rb b/lib/twingly/url.rb
index 20b4437..4999fd6 100644
--- a/lib/twingly/url.rb
+++ b/lib/twingly/url.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "digest"
+
 require "addressable/idna/pure"
 require "addressable/uri"
 require "public_suffix"
@@ -23,6 +25,11 @@ module Twingly
       PublicSuffix::DomainInvalid,
     ].freeze
 
+    # Instantiate digest classes in a thread-safe manner
+    # This is important since we don't know how people will
+    # use this gem (if they require it in a thread safe way)
+    SHA256_DIGEST = Digest(:SHA256)
+
     private_constant :ACCEPTED_SCHEMES
     private_constant :CUSTOM_PSL
     private_constant :STARTS_WITH_WWW
@@ -193,6 +200,14 @@ module Twingly
       self.to_s <=> other.to_s
     end
 
+    def eql?(other)
+      self.hash == other.hash
+    end
+
+    def hash
+      SHA256_DIGEST.digest(self.to_s).unpack1("q")
+    end
+
     def to_s
       addressable_uri.to_s
     end
diff --git a/lib/twingly/url/null_url.rb b/lib/twingly/url/null_url.rb
index 1044303..1d5e442 100644
--- a/lib/twingly/url/null_url.rb
+++ b/lib/twingly/url/null_url.rb
@@ -24,6 +24,14 @@ module Twingly
         self.to_s <=> other.to_s
       end
 
+      def eql?(other)
+        self.hash == other.hash
+      end
+
+      def hash
+        "".hash
+      end
+
       def to_s
         ""
       end
diff --git a/spec/lib/twingly/url/null_url_spec.rb b/spec/lib/twingly/url/null_url_spec.rb
index 7ae42c1..181e1ae 100644
--- a/spec/lib/twingly/url/null_url_spec.rb
+++ b/spec/lib/twingly/url/null_url_spec.rb
@@ -97,4 +97,9 @@ describe Twingly::URL::NullURL do
       expect { url.method_does_not_exist }.to raise_error(NoMethodError)
     end
   end
+
+  describe "uniqueness" do
+    subject(:list) { 10.times.map { |_| described_class.new }.uniq }
+    it { is_expected.to eq([described_class.new]) }
+  end
 end
diff --git a/spec/lib/twingly/url_spec.rb b/spec/lib/twingly/url_spec.rb
index 02614cc..f505d2f 100644
--- a/spec/lib/twingly/url_spec.rb
+++ b/spec/lib/twingly/url_spec.rb
@@ -847,6 +847,18 @@ describe Twingly::URL do
     end
   end
 
+  describe "uniqueness" do
+    context do "with the same URL twice"
+      let(:a) { described_class.parse("https://www.twingly.com/") }
+      let(:b) { described_class.parse("https://www.google.com/") }
+      let(:c) { described_class.parse("https://www.twingly.com/") }
+
+      it "only unique URLs" do
+        expect([a,b,c].uniq).to eq([a,b])
+      end
+    end
+  end
+
   describe "#inspect" do
     let(:url_object) { described_class.parse(url) }
     subject { url_object.inspect }

Example:

$ bundle exec pry
[1] pry(main)> require_relative "lib/twingly/url"
=> true
[2] pry(main)> 1000.times.map { Twingly::URL.parse(%Q{https://#{["www.", ""].sample}duh.se/}) }.uniq
=> [#<Twingly::URL:0x3ff188258e60 https://duh.se/>, #<Twingly::URL:0x3ff18824453c https://www.duh.se/>]
[3] pry(main)> 1000.times.map { Twingly::URL.parse(%Q{https://#{["www.", ""].sample}duh.se/}).normalized }.uniq
=> [#<Twingly::URL:0x3ff1881f4794 https://www.duh.se/>]

[dentarg]

Nice!