From e031ac9b27bb3c76d318107edf8178c60ff67b21 Mon Sep 17 00:00:00 2001
From: Martin Desrumaux <GNUletik@users.noreply.github.com>
Date: Wed, 14 Jun 2017 22:18:07 +0200
Subject: [PATCH] Allow filters to sort & select based on subvalues (#5622)

Merge pull request 5622
---
 lib/jekyll/filters.rb | 4 +++-
 test/test_filters.rb  | 6 ++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/jekyll/filters.rb b/lib/jekyll/filters.rb
index c8da0e52..e15cf7c6 100644
--- a/lib/jekyll/filters.rb
+++ b/lib/jekyll/filters.rb
@@ -361,7 +361,9 @@ module Jekyll
     private
     def item_property(item, property)
       if item.respond_to?(:to_liquid)
-        item.to_liquid[property.to_s]
+        property.to_s.split(".").reduce(item.to_liquid) do |subvalue, attribute|
+          subvalue[attribute]
+        end
       elsif item.respond_to?(:data)
         item.data[property.to_s]
       else
diff --git a/test/test_filters.rb b/test/test_filters.rb
index 243f97af..93ddb2cd 100644
--- a/test/test_filters.rb
+++ b/test/test_filters.rb
@@ -949,6 +949,12 @@ class TestFilters < JekyllUnitTest
         assert_equal [{ "a" => 1 }, { "a" => 2 }, { "b" => 1 }],
           @filter.sort([{ "a" => 2 }, { "b" => 1 }, { "a" => 1 }], "a", "last")
       end
+      should "return sorted by subproperty array" do
+        assert_equal [{ "a" => { "b" => 1 } }, { "a" => { "b" => 2 } },
+                      { "a" => { "b" => 3 } }, ],
+          @filter.sort([{ "a" => { "b" => 2 } }, { "a" => { "b" => 1 } },
+                        { "a" => { "b" => 3 } }, ], "a.b")
+      end
     end
 
     context "to_integer filter" do