Use Liquid::Utils.to_s for join filter (#1897)

lib/liquid/standardfilters.rb

@@ -1063,7 +1063,18 @@ module Liquid
       end
 
       def join(glue)
-        to_a.join(glue.to_s)
+        first = true
+        output = +""
+        @input.each do |item|
+          if first
+            first = false
+          else
+            output << glue
+          end
+
+          output << Liquid::Utils.to_s(item)
+        end
+        output
       end
 
       def concat(args)

test/integration/hash_rendering_test.rb

@@ -77,6 +77,12 @@ class HashRenderingTest < Minitest::Test
     assert_template_result("{\"numbers\"=>[{:foo=>42}]}", "{{ my_hash }}", { "my_hash" => { "numbers" => [{ foo: 42 }] } })
   end
 
+  def test_join_filter_with_hash
+    array = [{ "key1" => "value1" }, { "key2" => "value2" }]
+    glue = { "lol" => "wut" }
+    assert_template_result("{\"key1\"=>\"value1\"}{\"lol\"=>\"wut\"}{\"key2\"=>\"value2\"}", "{{ my_array | join: glue }}", { "my_array" => array, "glue" => glue })
+  end
+
   def test_render_hash_with_hash_key
     assert_template_result("{{\"foo\"=>\"bar\"}=>42}", "{{ my_hash }}", { "my_hash" => { Hash["foo" => "bar"] => 42 } })
   end