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

5 files changed, 40 insertions, 3 deletions

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index 64393b4089..ba1c7936b3 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   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
diff --git a/actionview/lib/action_view/digestor.rb b/actionview/lib/action_view/digestor.rb
index 9324a1ac50..a674e4d7ea 100644
--- a/actionview/lib/action_view/digestor.rb
+++ b/actionview/lib/action_view/digestor.rb
@@ -7,10 +7,14 @@ module ActionView
     @@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
 
diff --git a/actionview/test/fixtures/digestor/level/_recursion.html.erb b/actionview/test/fixtures/digestor/level/_recursion.html.erb
new file mode 100644
index 0000000000..ee5aaf09c3
--- /dev/null
+++ b/actionview/test/fixtures/digestor/level/_recursion.html.erb
@@ -0,0 +1 @@
+<%= render 'recursion' %>
diff --git a/actionview/test/fixtures/digestor/level/recursion.html.erb b/actionview/test/fixtures/digestor/level/recursion.html.erb
new file mode 100644
index 0000000000..ee5aaf09c3
--- /dev/null
+++ b/actionview/test/fixtures/digestor/level/recursion.html.erb
@@ -0,0 +1 @@
+<%= render 'recursion' %>
diff --git a/actionview/test/template/digestor_test.rb b/actionview/test/template/digestor_test.rb
index 06735c30d3..07f8d36d93 100644
--- a/actionview/test/template/digestor_test.rb
+++ b/actionview/test/template/digestor_test.rb
@@ -95,6 +95,31 @@ class TemplateDigestorTest < ActionView::TestCase
     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