Turn lookup context in to a stack, push and pop if formats change

This commit keeps a stack of lookup contexts on the ActionView::Base
instance.  If a format is passed to render, we instantiate a new lookup
context and push it on the stack, that way any child calls to "render"
will use the same format information as the parent.  This also isolates
"sibling" calls to render (multiple calls to render in the same
template).

Fixes #35222 #34138

6 files changed, 56 insertions, 23 deletions

diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index 420136d6de..37ecd84792 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -196,10 +196,9 @@ module ActionView #:nodoc:
       end
     end
 
-    attr_reader :view_renderer
+    attr_reader :view_renderer, :lookup_context
     attr_internal :config, :assigns
 
-    delegate :lookup_context, to: :view_renderer
     delegate :formats, :formats=, :locale, :locale=, :view_paths, :view_paths=, to: :lookup_context
 
     def assign(new_assigns) # :nodoc:
@@ -208,12 +207,17 @@ module ActionView #:nodoc:
 
     # :stopdoc:
 
-    def self.build_renderer(context, controller, formats)
-      lookup_context = context.is_a?(ActionView::LookupContext) ?
-        context : ActionView::LookupContext.new(context)
-      lookup_context.formats  = formats if formats
-      lookup_context.prefixes = controller._prefixes if controller
-      ActionView::Renderer.new(lookup_context)
+    def self.build_lookup_context(context, controller, formats)
+      case context
+      when ActionView::Renderer
+        context.lookup_context
+      when Array
+        ActionView::LookupContext.new(context)
+      when nil
+        ActionView::LookupContext.new([])
+      else
+        raise NotImplementedError, context.class.name
+      end
     end
 
     def self.empty
@@ -225,14 +229,14 @@ module ActionView #:nodoc:
     end
 
     def self.with_context(context, assigns = {}, controller = nil)
-      new ActionView::Renderer.new(context), assigns, controller
+      new context, assigns, controller
     end
 
     NULL = Object.new
 
     # :startdoc:
 
-    def initialize(renderer = nil, assigns = {}, controller = nil, formats = NULL) #:nodoc:
+    def initialize(lookup_context = nil, assigns = {}, controller = nil, formats = NULL) #:nodoc:
       @_config = ActiveSupport::InheritableOptions.new
 
       if formats == NULL
@@ -243,16 +247,19 @@ module ActionView #:nodoc:
         eowarn
       end
 
-      if renderer.is_a?(ActionView::Renderer)
-        @view_renderer = renderer
+      case lookup_context
+      when ActionView::LookupContext
+        @lookup_context = lookup_context
       else
         ActiveSupport::Deprecation.warn <<~eowarn
-        ActionView::Base instances should be constructed with a view renderer,
+        ActionView::Base instances should be constructed with a lookup context,
         assigments, and a controller.
         eowarn
-        @view_renderer = self.class.build_renderer(renderer, controller, formats)
+        @lookup_context = self.class.build_lookup_context(lookup_context, controller, formats)
       end
 
+      @view_renderer = ActionView::Renderer.new @lookup_context
+
       @cache_hit = {}
       assign(assigns)
       assign_controller(controller)
@@ -275,6 +282,25 @@ module ActionView #:nodoc:
       msg
     end
 
+    def in_context(options, locals)
+      old_view_renderer  = @view_renderer
+      old_lookup_context = @lookup_context
+
+      if !lookup_context.html_fallback_for_js && options[:formats]
+        formats = Array(options[:formats])
+        if formats == [:js]
+          formats << :html
+        end
+        @lookup_context = lookup_context.with_prepended_formats(formats)
+        @view_renderer = ActionView::Renderer.new @lookup_context
+      end
+
+      yield @view_renderer
+    ensure
+      @view_renderer = old_view_renderer
+      @lookup_context = old_lookup_context
+    end
+
     ActiveSupport.run_load_hooks(:action_view, self)
   end
 end
diff --git a/actionview/lib/action_view/helpers/rendering_helper.rb b/actionview/lib/action_view/helpers/rendering_helper.rb
index 1e12aa2736..7323963c72 100644
--- a/actionview/lib/action_view/helpers/rendering_helper.rb
+++ b/actionview/lib/action_view/helpers/rendering_helper.rb
@@ -27,10 +27,12 @@ module ActionView
       def render(options = {}, locals = {}, &block)
         case options
         when Hash
-          if block_given?
-            view_renderer.render_partial(self, options.merge(partial: options[:layout]), &block)
-          else
-            view_renderer.render(self, options)
+          in_context(options, locals) do |renderer|
+            if block_given?
+              view_renderer.render_partial(self, options.merge(partial: options[:layout]), &block)
+            else
+              view_renderer.render(self, options)
+            end
           end
         else
           view_renderer.render_partial(self, partial: options, locals: locals, &block)
diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index 61fe11cf45..125ab4dbe3 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -260,6 +260,13 @@ module ActionView
       @digest_cache ||= DetailsKey.digest_cache(@details)
     end
 
+    def with_prepended_formats(formats)
+      details = @details.dup
+      details[:formats] = formats
+
+      self.class.new(@view_paths, details, @prefixes)
+    end
+
     def initialize_details(target, details)
       registered_details.each do |k|
         target[k] = details[k] || Accessors::DEFAULT_PROCS[k].call
diff --git a/actionview/lib/action_view/renderer/partial_renderer.rb b/actionview/lib/action_view/renderer/partial_renderer.rb
index 801916954f..800a62eaa1 100644
--- a/actionview/lib/action_view/renderer/partial_renderer.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer.rb
@@ -379,8 +379,6 @@ module ActionView
         @locals  = options[:locals] || {}
         @details = extract_details(options)
 
-        prepend_formats(options[:formats])
-
         partial = options[:partial]
 
         if String === partial
diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index da92ce1f5e..b798e80b04 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -82,7 +82,7 @@ module ActionView
     #
     # Override this method in a module to change the default behavior.
     def view_context
-      view_context_class.new(view_renderer, view_assigns, self)
+      view_context_class.new(lookup_context, view_assigns, self)
     end
 
     # Returns an object that is able to render templates.
@@ -112,7 +112,7 @@ module ActionView
         lookup_context.rendered_format = nil if options[:formats]
         lookup_context.variants = variant if variant
 
-        view_renderer.render(context, options)
+        context.view_renderer.render(context, options)
       end
 
       # Assign the rendered format to look up context.
diff --git a/actionview/lib/action_view/template/handlers/erb/erubi.rb b/actionview/lib/action_view/template/handlers/erb/erubi.rb
index 15ca202024..20510c3062 100644
--- a/actionview/lib/action_view/template/handlers/erb/erubi.rb
+++ b/actionview/lib/action_view/template/handlers/erb/erubi.rb
@@ -26,7 +26,7 @@ module ActionView
             view = Class.new(ActionView::Base) {
               include action_view_erb_handler_context._routes.url_helpers
               class_eval("define_method(:_template) { |local_assigns, output_buffer| #{src} }", @filename || "(erubi)", 0)
-            }.with_context(action_view_erb_handler_context)
+            }.empty
             view.run(:_template, {}, ActionView::OutputBuffer.new)
           end