Pass source to template handler and deprecate old style handler

This commit passes the mutated source to the template handler as a
parameter and deprecates the old handlers.  Old handlers required that
templates contain a reference to mutated source code, but we would like
to make template objects "read only".  This change lets the template
remain "read only" while still giving template handlers access to the
source code after mutations.

actionview/lib/action_view/template.rb

@@ -2,7 +2,6 @@
 
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/kernel/singleton_class"
-require "active_support/deprecation"
 require "thread"
 require "delegate"
 
@@ -304,7 +303,7 @@ module ActionView
       # regardless of the original source encoding.
       def compile(mod)
         source = encode!
-        code = @handler.call(LegacyTemplate.new(self, source))
+        code = @handler.call(self, source)
 
         # Make sure that the resulting String to be eval'd is in the
         # encoding of the code

actionview/lib/action_view/template/handlers.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/deprecation"
+
 module ActionView #:nodoc:
   # = Action View Template Handlers
   class Template #:nodoc:
@@ -14,7 +16,7 @@ module ActionView #:nodoc:
         base.register_template_handler :erb, ERB.new
         base.register_template_handler :html, Html.new
         base.register_template_handler :builder, Builder.new
-        base.register_template_handler :ruby, :source.to_proc
+        base.register_template_handler :ruby, lambda { |_, source| source }
       end
 
       @@template_handlers = {}
@@ -24,11 +26,35 @@ module ActionView #:nodoc:
         @@template_extensions ||= @@template_handlers.keys
       end
 
+      class LegacyHandlerWrapper < SimpleDelegator # :nodoc:
+        def call(view, source)
+          __getobj__.call(ActionView::Template::LegacyTemplate.new(view, source))
+        end
+      end
+
       # Register an object that knows how to handle template files with the given
       # extensions. This can be used to implement new template types.
       # The handler must respond to +:call+, which will be passed the template
       # and should return the rendered template as a String.
       def register_template_handler(*extensions, handler)
+        params = if handler.is_a?(Proc)
+          handler.parameters
+        else
+          handler.method(:call).parameters
+        end
+
+        unless params.find_all { |type, _| type == :req }.length >= 2
+          ActiveSupport::Deprecation.warn <<~eowarn
+          Single arity template handlers are deprecated.  Template handlers must
+          now accept two parameters, the view object and the source for the view object.
+          Change:
+            >> #{handler.class}#call(#{params.map(&:last).join(", ")})
+          To:
+            >> #{handler.class}#call(#{params.map(&:last).join(", ")}, source)
+          eowarn
+          handler = LegacyHandlerWrapper.new(handler)
+        end
+
         raise(ArgumentError, "Extension is required") if extensions.empty?
         extensions.each do |extension|
           @@template_handlers[extension.to_sym] = handler

actionview/lib/action_view/template/handlers/builder.rb

@@ -5,11 +5,11 @@ module ActionView
     class Builder
       class_attribute :default_format, default: :xml
 
-      def call(template)
+      def call(template, source)
         require_engine
         "xml = ::Builder::XmlMarkup.new(:indent => 2);" \
           "self.output_buffer = xml.target!;" +
-          template.source +
+          source +
           ";xml.target!;"
       end
 

actionview/lib/action_view/template/handlers/erb.rb

@@ -28,8 +28,8 @@ module ActionView
 
         ENCODING_TAG = Regexp.new("\\A(<%#{ENCODING_FLAG}-?%>)[ \\t]*")
 
-        def self.call(template)
-          new.call(template)
+        def self.call(template, source)
+          new.call(template, source)
         end
 
         def supports_streaming?
@@ -40,17 +40,17 @@ module ActionView
           true
         end
 
-        def call(template)
+        def call(template, source)
           # First, convert to BINARY, so in case the encoding is
           # wrong, we can still find an encoding tag
           # (<%# encoding %>) inside the String using a regular
           # expression
-          template_source = template.source.dup.force_encoding(Encoding::ASCII_8BIT)
+          template_source = source.dup.force_encoding(Encoding::ASCII_8BIT)
 
           erb = template_source.gsub(ENCODING_TAG, "")
           encoding = $2
 
-          erb.force_encoding valid_encoding(template.source.dup, encoding)
+          erb.force_encoding valid_encoding(source.dup, encoding)
 
           # Always make sure we return a String in the default_internal
           erb.encode!

actionview/lib/action_view/template/handlers/html.rb

@@ -3,7 +3,7 @@
 module ActionView
   module Template::Handlers
     class Html < Raw
-      def call(template)
+      def call(template, source)
         "ActionView::OutputBuffer.new #{super}"
       end
     end

actionview/lib/action_view/template/handlers/raw.rb

@@ -3,8 +3,8 @@
 module ActionView
   module Template::Handlers
     class Raw
-      def call(template)
-        "#{template.source.inspect}.html_safe;"
+      def call(template, source)
+        "#{source.inspect}.html_safe;"
       end
     end
   end

actionview/test/abstract_unit.rb

@@ -58,7 +58,7 @@ module RenderERBUtils
     template = ActionView::Template.new(
       string.strip,
       "test template",
-      ActionView::Template::Handlers::ERB,
+      ActionView::Template.handler_for_extension(:erb),
       {})
 
     template.render(ActionView::Base.empty, {}).strip

actionview/test/actionpack/controller/layout_test.rb

@@ -70,7 +70,7 @@ class LayoutAutoDiscoveryTest < ActionController::TestCase
   end
 
   def test_third_party_template_library_auto_discovers_layout
-    with_template_handler :mab, lambda { |template| template.source.inspect } do
+    with_template_handler :mab, lambda { |template, source| source.inspect } do
       @controller = ThirdPartyTemplateLibraryController.new
       get :hello
       assert_response :success
@@ -212,7 +212,7 @@ class LayoutSetInResponseTest < ActionController::TestCase
   end
 
   def test_layout_set_when_using_render
-    with_template_handler :mab, lambda { |template| template.source.inspect } do
+    with_template_handler :mab, lambda { |template, source| source.inspect } do
       @controller = SetsLayoutInRenderController.new
       get :hello
       assert_includes @response.body, "layouts/third_party_template_library.mab"

actionview/test/template/dependency_tracker_test.rb

@@ -17,8 +17,8 @@ class FakeTemplate
   end
 end
 
-Neckbeard = lambda { |template| template.source }
-Bowtie = lambda { |template| template.source }
+Neckbeard = lambda { |template, source| source }
+Bowtie = lambda { |template, source| source }
 
 class DependencyTrackerTest < ActionView::TestCase
   def tracker

actionview/test/template/render_test.rb

@@ -450,13 +450,22 @@ module RenderTestCases
     assert_equal "Hello, World!", @view.render(inline: "Hello, World!", type: :bar)
   end
 
-  CustomHandler = lambda do |template|
+  CustomHandler = lambda do |template, source|
     "@output_buffer = ''.dup\n" \
-      "@output_buffer << 'source: #{template.source.inspect}'\n"
+      "@output_buffer << 'source: #{source.inspect}'\n"
   end
 
   def test_render_inline_with_render_from_to_proc
-    ActionView::Template.register_template_handler :ruby_handler, :source.to_proc
+    ActionView::Template.register_template_handler :ruby_handler, lambda { |_, source| source }
+    assert_equal "3", @view.render(inline: "(1 + 2).to_s", type: :ruby_handler)
+  ensure
+    ActionView::Template.unregister_template_handler :ruby_handler
+  end
+
+  def test_render_inline_with_render_from_to_proc_deprecated
+    assert_deprecated do
+      ActionView::Template.register_template_handler :ruby_handler, :source.to_proc
+    end
     assert_equal "3", @view.render(inline: "(1 + 2).to_s", type: :ruby_handler)
   ensure
     ActionView::Template.unregister_template_handler :ruby_handler