From af66bc8a5f9ae29fa8121c418675d43f3f755a03 Mon Sep 17 00:00:00 2001
From: Adam Klingbaum <adam.klingbaum@shopify.com>
Date: Thu, 15 Jun 2023 18:57:57 +0000
Subject: [PATCH] Add `sum` filter to standard filters

---
 lib/liquid/standardfilters.rb            | 25 +++++++++++
 test/integration/standard_filter_test.rb | 54 ++++++++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/lib/liquid/standardfilters.rb b/lib/liquid/standardfilters.rb
index 53662fef..aee43034 100644
--- a/lib/liquid/standardfilters.rb
+++ b/lib/liquid/standardfilters.rb
@@ -869,6 +869,31 @@ module Liquid
       false_check || (input.respond_to?(:empty?) && input.empty?) ? default_value : input
     end
 
+    # @liquid_public_docs
+    # @liquid_type filter
+    # @liquid_category array
+    # @liquid_summary
+    #   Returns the sum of all elements in an array.
+    # @liquid_syntax array | sum
+    # @liquid_return [number]
+    def sum(input, property = nil)
+      ary = InputIterator.new(input, context)
+
+      if ary.empty?
+        0
+      elsif property.nil?
+        ary.sum do |item|
+          Utils.to_number(item)
+        end
+      else
+        ary.sum do |item|
+          item.respond_to?(:[]) ? Utils.to_number(item[property]) : 0
+        rescue TypeError
+          raise_property_error(property)
+        end
+      end
+    end
+
     private
 
     attr_reader :context
diff --git a/test/integration/standard_filter_test.rb b/test/integration/standard_filter_test.rb
index bc8c6a4a..dd15ff4e 100644
--- a/test/integration/standard_filter_test.rb
+++ b/test/integration/standard_filter_test.rb
@@ -928,6 +928,60 @@ class StandardFiltersTest < Minitest::Test
     assert_equal([{ "foo" => true }, { "foo" => "for sure" }], @filters.where(input, "foo"))
   end
 
+  def test_sum_with_all_numbers
+    input = [1, 2]
+
+    assert_equal(3, @filters.sum(input))
+    assert_raises(Liquid::ArgumentError, "cannot select the property 'quantity'") do
+      @filters.sum(input, "quantity")
+    end
+  end
+
+  def test_sum_with_numeric_strings
+    input = [1, 2, "3", "4"]
+
+    assert_equal(10, @filters.sum(input))
+    assert_raises(Liquid::ArgumentError, "cannot select the property 'quantity'") do
+      @filters.sum(input, "quantity")
+    end
+  end
+
+  def test_sum_with_nested_arrays
+    input = [1, [2, [3, 4]]]
+
+    assert_equal(10, @filters.sum(input))
+    assert_raises(Liquid::ArgumentError, "cannot select the property 'quantity'") do
+      @filters.sum(input, "quantity")
+    end
+  end
+
+  def test_sum_with_indexable_map_values
+    input = [{ "quantity" => 1 }, { "quantity" => 2, "weight" => 3 }, { "weight" => 4 }]
+
+    assert_equal(0, @filters.sum(input))
+    assert_equal(3, @filters.sum(input, "quantity"))
+    assert_equal(7, @filters.sum(input, "weight"))
+    assert_equal(0, @filters.sum(input, "subtotal"))
+  end
+
+  def test_sum_with_indexable_non_map_values
+    input = [1, [2], "foo", { "quantity" => 3 }]
+
+    assert_equal(3, @filters.sum(input))
+    assert_raises(Liquid::ArgumentError, "cannot select the property 'quantity'") do
+      @filters.sum(input, "quantity")
+    end
+  end
+
+  def test_sum_with_unindexable_values
+    input = [1, true, nil, { "quantity" => 2 }]
+
+    assert_equal(1, @filters.sum(input))
+    assert_raises(Liquid::ArgumentError, "cannot select the property 'quantity'") do
+      @filters.sum(input, "quantity")
+    end
+  end
+
   private
 
   def with_timezone(tz)