require 'active_support/core_ext/array/wrap'
require 'active_support/core_ext/object/blank'
require 'active_support/core_ext/kernel/singleton_class'
module ActionView
class Template
extend ActiveSupport::Autoload
# === Encodings in ActionView::Template
#
# ActionView::Template is one of a few sources of potential
# encoding issues in Rails. This is because the source for
# templates are usually read from disk, and Ruby (like most
# encoding-aware programming languages) assumes that the
# String retrieved through File IO is encoded in the
# <tt>default_external</tt> encoding. In Rails, the default
# <tt>default_external</tt> encoding is UTF-8.
#
# As a result, if a user saves their template as ISO-8859-1
# (for instance, using a non-Unicode-aware text editor),
# and uses characters outside of the ASCII range, their
# users will see diamonds with question marks in them in
# the browser.
#
# To mitigate this problem, we use a few strategies:
# 1. If the source is not valid UTF-8, we raise an exception
# when the template is compiled to alert the user
# to the problem.
# 2. The user can specify the encoding using Ruby-style
# encoding comments in any template engine. If such
# a comment is supplied, Rails will apply that encoding
# to the resulting compiled source returned by the
# template handler.
# 3. In all cases, we transcode the resulting String to
# the <tt>default_internal</tt> encoding (which defaults
# to UTF-8).
#
# This means that other parts of Rails can always assume
# that templates are encoded in UTF-8, even if the original
# source of the template was not UTF-8.
#
# From a user's perspective, the easiest thing to do is
# to save your templates as UTF-8. If you do this, you
# do not need to do anything else for things to "just work".
#
# === Instructions for template handlers
#
# The easiest thing for you to do is to simply ignore
# encodings. Rails will hand you the template source
# as the default_internal (generally UTF-8), raising
# an exception for the user before sending the template
# to you if it could not determine the original encoding.
#
# For the greatest simplicity, you can support only
# UTF-8 as the <tt>default_internal</tt>. This means
# that from the perspective of your handler, the
# entire pipeline is just UTF-8.
#
# === Advanced: Handlers with alternate metadata sources
#
# If you want to provide an alternate mechanism for
# specifying encodings (like ERB does via <%# encoding: ... %>),
# you may indicate that you are willing to accept
# BINARY data by implementing <tt>self.accepts_binary?</tt>
# on your handler.
#
# If you do, Rails will not raise an exception if
# the template's encoding could not be determined,
# assuming that you have another mechanism for
# making the determination.
#
# In this case, make sure you return a String from
# your handler encoded in the default_internal. Since
# you are handling out-of-band metadata, you are
# also responsible for alerting the user to any
# problems with converting the user's data to
# the default_internal.
#
# To do so, simply raise the raise WrongEncodingError
# as follows:
#
# raise WrongEncodingError.new(
# problematic_string,
# expected_encoding
# )
eager_autoload do
autoload :Error
autoload :Handler
autoload :Handlers
autoload :Text
end
extend Template::Handlers
attr_reader :source, :identifier, :handler, :virtual_path, :formats,
:original_encoding
Finalizer = proc do |method_name, mod|
proc do
mod.module_eval do
remove_possible_method method_name
end
end
end
def initialize(source, identifier, handler, details)
@source = source
@identifier = identifier
@handler = handler
@original_encoding = nil
@virtual_path = details[:virtual_path]
@method_names = {}
format = details[:format] || :html
@formats = Array.wrap(format).map(&:to_sym)
end
def render(view, locals, &block)
# Notice that we use a bang in this instrumentation because you don't want to
# consume this in production. This is only slow if it's being listened to.
ActiveSupport::Notifications.instrument("!render_template.action_view", :virtual_path => @virtual_path) do
if view.is_a?(ActionView::CompiledTemplates)
mod = ActionView::CompiledTemplates
else
mod = view.singleton_class
end
method_name = compile(locals, view, mod)
view.send(method_name, locals, &block)
end
rescue Exception => e
if e.is_a?(Template::Error)
e.sub_template_of(self)
raise e
else
raise Template::Error.new(self, view.respond_to?(:assigns) ? view.assigns : {}, e)
end
end
def mime_type
@mime_type ||= Mime::Type.lookup_by_extension(@formats.first.to_s) if @formats.first
end
def variable_name
@variable_name ||= @virtual_path[%r'_?(\w+)(\.\w+)*$', 1].to_sym
end
def counter_name
@counter_name ||= "#{variable_name}_counter".to_sym
end
def inspect
if defined?(Rails.root)
identifier.sub("#{Rails.root}/", '')
else
identifier
end
end
private
# Among other things, this method is responsible for properly setting
# the encoding of the source. Until this point, we assume that the
# source is BINARY data. If no additional information is supplied,
# we assume the encoding is the same as Encoding.default_external.
#
# The user can also specify the encoding via a comment on the first
# line of the template (# encoding: NAME-OF-ENCODING). This will work
# with any template engine, as we process out the encoding comment
# before passing the source on to the template engine, leaving a
# blank line in its stead.
#
# Note that after we figure out the correct encoding, we then
# encode the source into Encoding.default_internal. In general,
# this means that templates will be UTF-8 inside of Rails,
# regardless of the original source encoding.
def compile(locals, view, mod)
method_name = build_method_name(locals)
return method_name if view.respond_to?(method_name)
locals_code = locals.keys.map! { |key| "#{key} = local_assigns[:#{key}];" }.join
if source.encoding_aware?
if source.sub!(/\A#{ENCODING_FLAG}/, '')
encoding = $1
else
encoding = Encoding.default_external
end
# Tag the source with the default external encoding
# or the encoding specified in the file
source.force_encoding(encoding)
# If the original encoding is BINARY, the actual
# encoding is either stored out-of-band (such as
# in ERB <%# %> style magic comments) or missing.
# This is also true if the original encoding is
# something other than BINARY, but it's invalid.
if source.encoding != Encoding::BINARY && source.valid_encoding?
source.encode!
# If the assumed encoding is incorrect, check to
# see whether the handler accepts BINARY. If it
# does, it has another mechanism for determining
# the true encoding of the String.
elsif @handler.respond_to?(:accepts_binary?) && @handler.accepts_binary?
source.force_encoding(Encoding::BINARY)
# If the handler does not accept BINARY, the
# assumed encoding (either the default_external,
# or the explicit encoding specified by the user)
# is incorrect. We raise an exception here.
else
raise WrongEncodingError.new(source, encoding)
end
# Don't validate the encoding yet -- the handler
# may treat the String as raw bytes and extract
# the encoding some other way
end
code = @handler.call(self)
source = <<-end_src
def #{method_name}(local_assigns)
_old_virtual_path, @_virtual_path = @_virtual_path, #{@virtual_path.inspect};_old_output_buffer = @output_buffer;#{locals_code};#{code}
ensure
@_virtual_path, @output_buffer = _old_virtual_path, _old_output_buffer
end
end_src
if source.encoding_aware?
# Handlers should return their source Strings in either the
# default_internal or BINARY. If the handler returns a BINARY
# String, we assume its encoding is the one we determined
# earlier, and encode the resulting source in the default_internal.
if source.encoding == Encoding::BINARY
source.force_encoding(Encoding.default_internal)
end
# In case we get back a String from a handler that is not in
# BINARY or the default_internal, encode it to the default_internal
source.encode!
# Now, validate that the source we got back from the template
# handler is valid in the default_internal
unless source.valid_encoding?
raise WrongEncodingError.new(@source, Encoding.default_internal)
end
end
begin
mod.module_eval(source, identifier, 0)
ObjectSpace.define_finalizer(self, Finalizer[method_name, mod])
method_name
rescue Exception => e # errors from template code
if logger = (view && view.logger)
logger.debug "ERROR: compiling #{method_name} RAISED #{e}"
logger.debug "Function body: #{source}"
logger.debug "Backtrace: #{e.backtrace.join("\n")}"
end
raise ActionView::Template::Error.new(self, {}, e)
end
end
def build_method_name(locals)
# TODO: is locals.keys.hash reliably the same?
@method_names[locals.keys.hash] ||=
"_render_template_#{@identifier.hash}_#{__id__}_#{locals.keys.hash}".gsub('-', "_")
end
end
end
