Fix partial caching ignore repeated items issue

This is because we only use hash to maintain the result. So when the key
are the same, the result would be skipped. The solution is to maintain
an array for tracking every item's position to restructure the result.

2 files changed, 23 insertions, 0 deletions

diff --git a/actionview/test/fixtures/test/_cached_set.erb b/actionview/test/fixtures/test/_cached_set.erb
new file mode 100644
index 0000000000..cd492fc519
--- /dev/null
+++ b/actionview/test/fixtures/test/_cached_set.erb
@@ -0,0 +1 @@
+<%= cached_set.first %> | <%= cached_set.second %> | <%= cached_set.third %> | <%= cached_set.fourth %> | <%= cached_set.fifth %>
diff --git a/actionview/test/template/render_test.rb b/actionview/test/template/render_test.rb
index 15c41051de..f0b5d7d95e 100644
--- a/actionview/test/template/render_test.rb
+++ b/actionview/test/template/render_test.rb
@@ -811,6 +811,28 @@ class CachedCollectionViewRenderTest < ActiveSupport::TestCase
     end
   end
 
+  test "collection caching with repeated collection" do
+    sets = [
+        [1, 2, 3, 4, 5],
+        [1, 2, 3, 4, 4],
+        [1, 2, 3, 4, 5],
+        [1, 2, 3, 4, 4],
+        [1, 2, 3, 4, 6]
+    ]
+
+    result = @view.render(partial: "test/cached_set", collection: sets, cached: true)
+
+    splited_result = result.split("\n")
+    assert_equal 5, splited_result.count
+    assert_equal [
+      "1 | 2 | 3 | 4 | 5",
+      "1 | 2 | 3 | 4 | 4",
+      "1 | 2 | 3 | 4 | 5",
+      "1 | 2 | 3 | 4 | 4",
+      "1 | 2 | 3 | 4 | 6"
+    ], splited_result
+  end
+
   private
     def cache_key(*names, virtual_path)
       digest = ActionView::Digestor.digest name: virtual_path, format: :html, finder: @view.lookup_context, dependencies: []