require 'active_support/core_ext/object/try'
require 'active_support/core_ext/kernel/singleton_class'
require 'thread'
module ActionView
# = Action View Template
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.
#
# For the rest of this documentation, when we say "UTF-8",
# we mean "UTF-8 or whatever the default_internal encoding
# is set to". By default, it will be UTF-8.
#
# 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 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 will handle encodings yourself
# by implementing <tt>self.handles_encoding?</tt>
# on your handler.
#
# If you do, Rails will not try to encode the String
# into the default_internal, passing you the unaltered
# bytes tagged with the assumed encoding (from
# default_external).
#
# 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 <tt>default_internal</tt>.
#
# To do so, simply raise +WrongEncodingError+ as follows:
#
# raise WrongEncodingError.new(
# problematic_string,
# expected_encoding
# )
eager_autoload do
autoload :Error
autoload :Handlers
autoload :Text
autoload :Types
end
extend Template::Handlers
attr_accessor :locals, :formats, :virtual_path
attr_reader :source, :identifier, :handler, :original_encoding, :updated_at
# This finalizer is needed (and exactly with a proc inside another proc)
# otherwise templates leak in development.
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)
format = details[:format] || (handler.default_format if handler.respond_to?(:default_format))
@source = source
@identifier = identifier
@handler = handler
@compiled = false
@original_encoding = nil
@locals = details[:locals] || []
@virtual_path = details[:virtual_path]
@updated_at = details[:updated_at] || Time.now
@formats = Array(format).map { |f| f.respond_to?(:ref) ? f.ref : f }
@compile_mutex = Mutex.new
end
# Returns if the underlying handler supports streaming. If so,
# a streaming buffer *may* be passed when it start rendering.
def supports_streaming?
handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
end
# Render a template. If the template was not compiled yet, it is done
# exactly before rendering.
#
# This method is instrumented as "!render_template.action_view". 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.
def render(view, locals, buffer=nil, &block)
instrument("!render_template") do
compile!(view)
view.send(method_name, locals, buffer, &block)
end
rescue Exception => e
handle_render_error(view, e)
end
def type
@type ||= Types[@formats.first] if @formats.first
end
# Receives a view object and return a template similar to self by using @virtual_path.
#
# This method is useful if you have a template object but it does not contain its source
# anymore since it was already compiled. In such cases, all you need to do is to call
# refresh passing in the view object.
#
# Notice this method raises an error if the template to be refreshed does not have a
# virtual path set (true just for inline templates).
def refresh(view)
raise "A template needs to have a virtual path in order to be refreshed" unless @virtual_path
lookup = view.lookup_context
pieces = @virtual_path.split("/")
name = pieces.pop
partial = !!name.sub!(/^_/, "")
lookup.disable_cache do
lookup.find_template(name, [ pieces.join('/') ], partial, @locals)
end
end
def inspect
@inspect ||= defined?(Rails.root) ? identifier.sub("#{Rails.root}/", '') : identifier
end
# 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 <tt>Encoding.default_external</tt>.
#
# 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.
def encode!
return unless source.encoding == Encoding::BINARY
# Look for # encoding: *. If we find one, we'll encode the
# String in that encoding, otherwise, we'll use the
# default external encoding.
if source.sub!(/\A#{ENCODING_FLAG}/, '')
encoding = magic_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 user didn't specify an encoding, and the handler
# handles encodings, we simply pass the String as is to
# the handler (with the default_external tag)
if !magic_encoding && @handler.respond_to?(:handles_encoding?) && @handler.handles_encoding?
source
# Otherwise, if the String is valid in the encoding,
# encode immediately to default_internal. This means
# that if a handler doesn't handle encodings, it will
# always get Strings in the default_internal
elsif source.valid_encoding?
source.encode!
# Otherwise, since the String is invalid in the encoding
# specified, raise an exception
else
raise WrongEncodingError.new(source, encoding)
end
end
protected
# Compile a template. This method ensures a template is compiled
# just once and removes the source after it is compiled.
def compile!(view) #:nodoc:
return if @compiled
# Templates can be used concurrently in threaded environments
# so compilation and any instance variable modification must
# be synchronized
@compile_mutex.synchronize do
# Any thread holding this lock will be compiling the template needed
# by the threads waiting. So re-check the @compiled flag to avoid
# re-compilation
return if @compiled
if view.is_a?(ActionView::CompiledTemplates)
mod = ActionView::CompiledTemplates
else
mod = view.singleton_class
end
instrument("!compile_template") do
compile(view, mod)
end
# Just discard the source if we have a virtual path. This
# means we can get the template back.
@source = nil if @virtual_path
@compiled = true
end
end
# Among other things, this method is responsible for properly setting
# the encoding of the compiled template.
#
# If the template engine handles encodings, we send the encoded
# String to the engine without further processing. This allows
# the template engine to support additional mechanisms for
# specifying the encoding. For instance, ERB supports <%# encoding: %>
#
# Otherwise, after we figure out the correct encoding, we then
# encode the source into <tt>Encoding.default_internal</tt>.
# In general, this means that templates will be UTF-8 inside of Rails,
# regardless of the original source encoding.
def compile(view, mod) #:nodoc:
encode!
method_name = self.method_name
code = @handler.call(self)
# Make sure that the resulting String to be evalled is in the
# encoding of the code
source = <<-end_src
def #{method_name}(local_assigns, output_buffer)
_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
# Make sure the source is in the encoding of the returned code
source.force_encoding(code.encoding)
# 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. This is for handlers
# that handle encoding but screw up
unless source.valid_encoding?
raise WrongEncodingError.new(@source, Encoding.default_internal)
end
begin
mod.module_eval(source, identifier, 0)
ObjectSpace.define_finalizer(self, Finalizer[method_name, mod])
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 handle_render_error(view, e) #:nodoc:
if e.is_a?(Template::Error)
e.sub_template_of(self)
raise e
else
template = self
unless template.source
template = refresh(view)
template.encode!
end
raise Template::Error.new(template, e)
end
end
def locals_code #:nodoc:
# Double assign to suppress the dreaded 'assigned but unused variable' warning
@locals.map { |key| "#{key} = #{key} = local_assigns[:#{key}];" }.join
end
def method_name #:nodoc:
@method_name ||= "_#{identifier_method_name}__#{@identifier.hash}_#{__id__}".gsub('-', "_")
end
def identifier_method_name #:nodoc:
inspect.gsub(/[^a-z_]/, '_')
end
def instrument(action, &block)
payload = { virtual_path: @virtual_path, identifier: @identifier }
ActiveSupport::Notifications.instrument("#{action}.action_view", payload, &block)
end
end
end
