Make backtrace_cleaner work as expected. Prior to this patch, the Full Trace rarely showed the full trace. Also, increase performance considerably.

actionpack/lib/action_view/template/error.rb

@@ -21,17 +21,18 @@ def initialize(paths, path, details, partial)
       super("Missing #{template_type} #{path} with #{details.inspect} in view paths #{display_paths}")
     end
   end
+
   class Template
     # The Template::Error exception is raised when the compilation of the template fails. This exception then gathers a
     # bunch of intimate details and uses it to report a very precise exception message.
     class Error < ActionViewError #:nodoc:
       SOURCE_CODE_RADIUS = 3
 
-      attr_reader :original_exception
+      attr_reader :original_exception, :backtrace
 
       def initialize(template, assigns, original_exception)
         @template, @assigns, @original_exception = template, assigns.dup, original_exception
-        @backtrace = compute_backtrace
+        @backtrace = original_exception.backtrace
       end
 
       def file_name
@@ -42,14 +43,6 @@ def message
         ActiveSupport::Deprecation.silence { original_exception.message }
       end
 
-      def clean_backtrace
-        if defined?(Rails) && Rails.respond_to?(:backtrace_cleaner)
-          Rails.backtrace_cleaner.clean(original_exception.backtrace)
-        else
-          original_exception.backtrace
-        end
-      end
-
       def sub_template_message
         if @sub_templates
           "Trace of template inclusion: " +
@@ -87,29 +80,16 @@ def line_number
         @line_number ||=
           if file_name
             regexp = /#{Regexp.escape File.basename(file_name)}:(\d+)/
-
-            $1 if message =~ regexp or clean_backtrace.find { |line| line =~ regexp }
+            $1 if message =~ regexp || backtrace.find { |line| line =~ regexp }
           end
       end
 
       def to_s
-        "\n#{self.class} (#{message}) #{source_location}:\n" +
-        "#{source_extract}\n    #{clean_backtrace.join("\n    ")}\n\n"
-      end
-
-      # don't do anything nontrivial here. Any raised exception from here becomes fatal
-      # (and can't be rescued).
-      def backtrace
-        @backtrace
+        "\n#{self.class} (#{message}) #{source_location}:\n\n" +
+        "#{source_extract(4)}\n    #{backtrace.join("\n    ")}\n\n"
       end
 
       private
-        def compute_backtrace
-          [
-            "#{source_location.capitalize}\n\n#{source_extract(4)}\n    " +
-            clean_backtrace.join("\n    ")
-          ]
-        end
 
         def source_location
           if line_number

railties/lib/rails/backtrace_cleaner.rb

@@ -2,29 +2,28 @@
 
 module Rails
   class BacktraceCleaner < ActiveSupport::BacktraceCleaner
-    ERB_METHOD_SIG = /:in `_run_erb_.*/
-    APP_DIRS = %w( app config lib test )
+    APP_DIRS_PATTERN = /^\/?(app|config|lib|test)/
+    RENDER_TEMPLATE_PATTERN = /:in `_render_template_\w*'/
 
     def initialize
       super
       add_filter   { |line| line.sub("#{Rails.root}/", '') }
-      add_filter   { |line| line.sub(ERB_METHOD_SIG, '') }
+      add_filter   { |line| line.sub(RENDER_TEMPLATE_PATTERN, '') }
       add_filter   { |line| line.sub('./', '/') } # for tests
 
       add_gem_filters
-
-      add_silencer { |line| !APP_DIRS.any? { |dir| line =~ /^\/?#{dir}/ } }
+      add_silencer { |line| line !~ APP_DIRS_PATTERN }
     end
 
     private
       def add_gem_filters
-        return unless defined? Gem
-        (Gem.path + [Gem.default_dir]).uniq.each do |path|
-          # http://gist.github.com/30430
-          add_filter { |line|
-            line.sub(%r{(#{path})/gems/([^/]+)-([0-9.]+)/(.*)}, '\2 (\3) \4')
-          }
-        end
+        return unless defined?(Gem)
+
+        gems_paths = (Gem.path + [Gem.default_dir]).uniq.map!{ |p| Regexp.escape(p) }
+        return if gems_paths.empty?
+
+        gems_regexp = %r{(#{gems_paths.join('|')})/gems/([^/]+)-([\w\.]+)/(.*)}
+        add_filter { |line| line.sub(gems_regexp, '\2 (\3) \4') }
       end
   end