Use to_liquid_value in uniq filter

lib/liquid/standardfilters.rb

@@ -1081,7 +1081,10 @@ module Liquid
       end
 
       def uniq(&block)
-        to_a.uniq(&block)
+        to_a.uniq do |item|
+          item = Utils.to_liquid_value(item)
+          block ? yield(item) : item
+        end
       end
 
       def compact

test/integration/standard_filter_test.rb

@@ -1340,6 +1340,22 @@ class StandardFiltersTest < Minitest::Test
     assert_equal(0, @filters.sum(input, ""))
   end
 
+  def test_uniq_with_to_liquid_value
+    input = [StringDrop.new("foo"), StringDrop.new("bar"), "foo"]
+    expected = [StringDrop.new("foo"), StringDrop.new("bar")]
+    result = @filters.uniq(input)
+
+    assert_equal(expected, result)
+  end
+
+  def test_uniq_with_to_liquid_value_pick_correct_classes
+    input = ["foo", StringDrop.new("foo"), StringDrop.new("bar")]
+    expected = [String, StringDrop]
+    result = @filters.uniq(input).map(&:class)
+
+    assert_equal(expected, result)
+  end
+
   private
 
   def with_timezone(tz)

test/test_helper.rb

@@ -146,6 +146,35 @@ class BooleanDrop < Liquid::Drop
   end
 end
 
+class StringDrop < Liquid::Drop
+  include Comparable
+
+  def initialize(value)
+    super()
+    @value = value
+  end
+
+  def to_liquid_value
+    @value
+  end
+
+  def to_s
+    @value
+  end
+
+  def to_str
+    @value
+  end
+
+  def inspect
+    "#<StringDrop @value=#{@value.inspect}>"
+  end
+
+  def <=>(other)
+    to_liquid_value <=> Liquid::Utils.to_liquid_value(other)
+  end
+end
+
 class ErrorDrop < Liquid::Drop
   def standard_error
     raise Liquid::StandardError, 'standard error'