Fix "Stack Level Too Deep" error when rendering recursive partials

When rendering recursive partial Action View is trying to generate the
view digest infinitly causing a stack level error.

Fixes #11340

actionview/CHANGELOG.md

+*   Fix "Stack Level Too Deep" error when redering recursive partials.
+
+    Fixes #11340.
+
+    *Rafael Mendonça França*
+
 *   Added an `enforce_utf8` hash option for `form_tag` method.
 
     Control to output a hidden input tag with name `utf8` without monkey

actionview/lib/action_view/digestor.rb

@@ -7,10 +7,14 @@ class Digestor
     @@cache = ThreadSafe::Cache.new
 
     def self.digest(name, format, finder, options = {})
-      cache_key = [name, format] + Array.wrap(options[:dependencies])
-      @@cache[cache_key.join('.')] ||= begin
+      cache_key = ([name, format] + Array.wrap(options[:dependencies])).join('.')
+      @@cache.fetch(cache_key) do
+        @@cache[cache_key] ||= nil if options[:partial] # Prevent re-entry
+
         klass = options[:partial] || name.include?("/_") ? PartialDigestor : Digestor
-        klass.new(name, format, finder, options).digest
+        digest = klass.new(name, format, finder, options).digest
+
+        @@cache[cache_key] = digest # Store the value
       end
     end
 

actionview/test/fixtures/digestor/level/_recursion.html.erb

+<%= render 'recursion' %>

actionview/test/fixtures/digestor/level/recursion.html.erb

+<%= render 'recursion' %>

actionview/test/template/digestor_test.rb

@@ -95,6 +95,31 @@ def test_nested_template_directory
     end
   end
 
+  def test_recursion_in_renders
+    assert digest("level/recursion") # assert recursion is possible
+    assert_not_nil digest("level/recursion") # assert digest is stored
+  end
+
+  def test_chaning_the_top_templete_on_recursion
+    assert digest("level/recursion") # assert recursion is possible
+
+    assert_digest_difference("level/recursion") do
+      change_template("level/recursion")
+    end
+
+    assert_not_nil digest("level/recursion") # assert digest is stored
+  end
+
+  def test_chaning_the_partial_templete_on_recursion
+    assert digest("level/recursion") # assert recursion is possible
+
+    assert_digest_difference("level/recursion") do
+      change_template("level/_recursion")
+    end
+
+    assert_not_nil digest("level/recursion") # assert digest is stored
+  end
+
   def test_dont_generate_a_digest_for_missing_templates
     assert_equal '', digest("nothing/there")
   end