From deb10ebc7a8b1979b7c5daec83f2e69d9b68591d Mon Sep 17 00:00:00 2001
From: Eric Chan <chanman_ca@yahoo.com>
Date: Thu, 14 Sep 2017 02:00:43 -0400
Subject: [PATCH] Sorting support for data with undefined values

---
 lib/liquid/standardfilters.rb            | 28 +++++++++++++++++-------
 test/integration/standard_filter_test.rb | 15 +++++++++++++
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/lib/liquid/standardfilters.rb b/lib/liquid/standardfilters.rb
index f14ba1d..34b4a49 100644
--- a/lib/liquid/standardfilters.rb
+++ b/lib/liquid/standardfilters.rb
@@ -121,17 +121,23 @@ module Liquid
     def sort(input, property = nil)
       ary = InputIterator.new(input)
       if property.nil?
-        ary.sort
+        ary.sort do |a, b|
+          if !a.nil? && !b.nil?
+            a <=> b
+          else
+            a.nil? ? 1 : -1
+          end
+        end
       elsif ary.empty? # The next two cases assume a non-empty array.
         []
-      elsif ary.first.respond_to?(:[]) && !ary.first[property].nil?
+      elsif ary.all? { |el| el.respond_to?(:[]) }
         ary.sort do |a, b|
           a = a[property]
           b = b[property]
-          if a && b
+          if !a.nil? && !b.nil?
             a <=> b
           else
-            a ? -1 : 1
+            a.nil? ? 1 : -1
           end
         end
       end
@@ -143,17 +149,23 @@ module Liquid
       ary = InputIterator.new(input)
 
       if property.nil?
-        ary.sort { |a, b| a.to_s.casecmp(b.to_s) }
+        ary.sort do |a, b|
+          if !a.nil? && !b.nil?
+            a.to_s.casecmp(b.to_s)
+          else
+            a.nil? ? 1 : -1
+          end
+        end
       elsif ary.empty? # The next two cases assume a non-empty array.
         []
-      elsif ary.first.respond_to?(:[]) && !ary.first[property].nil?
+      elsif ary.all? { |el| el.respond_to?(:[]) }
         ary.sort do |a, b|
           a = a[property]
           b = b[property]
-          if a && b
+          if !a.nil? && !b.nil?
             a.to_s.casecmp(b.to_s)
           else
-            a ? -1 : 1
+            a.nil? ? 1 : -1
           end
         end
       end
diff --git a/test/integration/standard_filter_test.rb b/test/integration/standard_filter_test.rb
index c53aae1..6c91f16 100644
--- a/test/integration/standard_filter_test.rb
+++ b/test/integration/standard_filter_test.rb
@@ -190,6 +190,11 @@ class StandardFiltersTest < Minitest::Test
     assert_equal [{ "a" => 1 }, { "a" => 2 }, { "a" => 3 }, { "a" => 4 }], @filters.sort([{ "a" => 4 }, { "a" => 3 }, { "a" => 1 }, { "a" => 2 }], "a")
   end
 
+  def test_sort_with_nils
+    assert_equal [1, 2, 3, 4, nil], @filters.sort([nil, 4, 3, 2, 1])
+    assert_equal [{ "a" => 1 }, { "a" => 2 }, { "a" => 3 }, { "a" => 4 }, {}], @filters.sort([{ "a" => 4 }, { "a" => 3 }, {}, { "a" => 1 }, { "a" => 2 }], "a")
+  end
+
   def test_sort_when_property_is_sometimes_missing_puts_nils_last
     input = [
       { "price" => 4, "handle" => "alpha" },
@@ -208,6 +213,16 @@ class StandardFiltersTest < Minitest::Test
     assert_equal expectation, @filters.sort(input, "price")
   end
 
+  def test_sort_natural
+    assert_equal ["a", "B", "c", "D"], @filters.sort_natural(["c", "D", "a", "B"])
+    assert_equal [{ "a" => "a" }, { "a" => "B" }, { "a" => "c" }, { "a" => "D" }], @filters.sort_natural([{ "a" => "D" }, { "a" => "c" }, { "a" => "a" }, { "a" => "B" }], "a")
+  end
+
+  def test_sort_natural_with_nils
+    assert_equal ["a", "B", "c", "D", nil], @filters.sort_natural([nil, "c", "D", "a", "B"])
+    assert_equal [{ "a" => "a" }, { "a" => "B" }, { "a" => "c" }, { "a" => "D" }, {}], @filters.sort_natural([{ "a" => "D" }, { "a" => "c" }, {}, { "a" => "a" }, { "a" => "B" }], "a")
+  end
+
   def test_sort_natural_when_property_is_sometimes_missing_puts_nils_last
     input = [
       { "price" => "4", "handle" => "alpha" },