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.

6 files changed, 38 insertions, 13 deletions

diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index 2d1762e568..3b2c264ed4 100644
--- a/actionview/lib/action_view/template.rb
+++ b/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
diff --git a/actionview/lib/action_view/template/handlers.rb b/actionview/lib/action_view/template/handlers.rb
index 7ec76dcc3f..f2a2341b8e 100644
--- a/actionview/lib/action_view/template/handlers.rb
+++ b/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
diff --git a/actionview/lib/action_view/template/handlers/builder.rb b/actionview/lib/action_view/template/handlers/builder.rb
index 61492ce448..e5413cd2a0 100644
--- a/actionview/lib/action_view/template/handlers/builder.rb
+++ b/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
 
diff --git a/actionview/lib/action_view/template/handlers/erb.rb b/actionview/lib/action_view/template/handlers/erb.rb
index 7d1a6767d7..b6314a5bc3 100644
--- a/actionview/lib/action_view/template/handlers/erb.rb
+++ b/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!
diff --git a/actionview/lib/action_view/template/handlers/html.rb b/actionview/lib/action_view/template/handlers/html.rb
index 27004a318c..65857d8587 100644
--- a/actionview/lib/action_view/template/handlers/html.rb
+++ b/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
diff --git a/actionview/lib/action_view/template/handlers/raw.rb b/actionview/lib/action_view/template/handlers/raw.rb
index 5cd23a0060..57ebb169fc 100644
--- a/actionview/lib/action_view/template/handlers/raw.rb
+++ b/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