359 lines
13 KiB
Ruby
359 lines
13 KiB
Ruby
require "active_support/core_ext/object/try"
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require "active_support/core_ext/kernel/singleton_class"
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require "thread"
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module ActionView
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# = Action View Template
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class Template
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extend ActiveSupport::Autoload
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# === Encodings in ActionView::Template
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#
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# ActionView::Template is one of a few sources of potential
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# encoding issues in Rails. This is because the source for
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# templates are usually read from disk, and Ruby (like most
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# encoding-aware programming languages) assumes that the
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# String retrieved through File IO is encoded in the
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# <tt>default_external</tt> encoding. In Rails, the default
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# <tt>default_external</tt> encoding is UTF-8.
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#
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# As a result, if a user saves their template as ISO-8859-1
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# (for instance, using a non-Unicode-aware text editor),
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# and uses characters outside of the ASCII range, their
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# users will see diamonds with question marks in them in
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# the browser.
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#
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# For the rest of this documentation, when we say "UTF-8",
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# we mean "UTF-8 or whatever the default_internal encoding
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# is set to". By default, it will be UTF-8.
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#
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# To mitigate this problem, we use a few strategies:
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# 1. If the source is not valid UTF-8, we raise an exception
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# when the template is compiled to alert the user
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# to the problem.
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# 2. The user can specify the encoding using Ruby-style
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# encoding comments in any template engine. If such
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# a comment is supplied, Rails will apply that encoding
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# to the resulting compiled source returned by the
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# template handler.
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# 3. In all cases, we transcode the resulting String to
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# the UTF-8.
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#
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# This means that other parts of Rails can always assume
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# that templates are encoded in UTF-8, even if the original
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# source of the template was not UTF-8.
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#
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# From a user's perspective, the easiest thing to do is
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# to save your templates as UTF-8. If you do this, you
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# do not need to do anything else for things to "just work".
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#
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# === Instructions for template handlers
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#
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# The easiest thing for you to do is to simply ignore
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# encodings. Rails will hand you the template source
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# as the default_internal (generally UTF-8), raising
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# an exception for the user before sending the template
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# to you if it could not determine the original encoding.
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#
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# For the greatest simplicity, you can support only
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# UTF-8 as the <tt>default_internal</tt>. This means
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# that from the perspective of your handler, the
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# entire pipeline is just UTF-8.
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#
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# === Advanced: Handlers with alternate metadata sources
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#
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# If you want to provide an alternate mechanism for
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# specifying encodings (like ERB does via <%# encoding: ... %>),
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# you may indicate that you will handle encodings yourself
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# by implementing <tt>handles_encoding?</tt> on your handler.
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#
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# If you do, Rails will not try to encode the String
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# into the default_internal, passing you the unaltered
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# bytes tagged with the assumed encoding (from
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# default_external).
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#
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# In this case, make sure you return a String from
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# your handler encoded in the default_internal. Since
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# you are handling out-of-band metadata, you are
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# also responsible for alerting the user to any
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# problems with converting the user's data to
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# the <tt>default_internal</tt>.
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#
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# To do so, simply raise +WrongEncodingError+ as follows:
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#
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# raise WrongEncodingError.new(
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# problematic_string,
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# expected_encoding
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# )
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##
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# :method: local_assigns
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#
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# Returns a hash with the defined local variables.
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#
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# Given this sub template rendering:
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#
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# <%= render "shared/header", { headline: "Welcome", person: person } %>
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#
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# You can use +local_assigns+ in the sub templates to access the local variables:
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#
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# local_assigns[:headline] # => "Welcome"
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eager_autoload do
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autoload :Error
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autoload :Handlers
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autoload :HTML
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autoload :Text
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autoload :Types
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end
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extend Template::Handlers
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attr_accessor :locals, :formats, :variants, :virtual_path
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attr_reader :source, :identifier, :handler, :original_encoding, :updated_at
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# This finalizer is needed (and exactly with a proc inside another proc)
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# otherwise templates leak in development.
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Finalizer = proc do |method_name, mod| # :nodoc:
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proc do
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mod.module_eval do
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remove_possible_method method_name
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end
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end
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end
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def initialize(source, identifier, handler, details)
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format = details[:format] || (handler.default_format if handler.respond_to?(:default_format))
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@source = source
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@identifier = identifier
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@handler = handler
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@compiled = false
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@original_encoding = nil
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@locals = details[:locals] || []
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@virtual_path = details[:virtual_path]
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@updated_at = details[:updated_at] || Time.now
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@formats = Array(format).map { |f| f.respond_to?(:ref) ? f.ref : f }
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@variants = [details[:variant]]
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@compile_mutex = Mutex.new
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end
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# Returns whether the underlying handler supports streaming. If so,
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# a streaming buffer *may* be passed when it starts rendering.
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def supports_streaming?
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handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
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end
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# Render a template. If the template was not compiled yet, it is done
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# exactly before rendering.
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#
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# This method is instrumented as "!render_template.action_view". Notice that
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# we use a bang in this instrumentation because you don't want to
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# consume this in production. This is only slow if it's being listened to.
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def render(view, locals, buffer = nil, &block)
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instrument_render_template do
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compile!(view)
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view.send(method_name, locals, buffer, &block)
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end
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rescue => e
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handle_render_error(view, e)
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end
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def type
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@type ||= Types[@formats.first] if @formats.first
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end
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# Receives a view object and return a template similar to self by using @virtual_path.
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#
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# This method is useful if you have a template object but it does not contain its source
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# anymore since it was already compiled. In such cases, all you need to do is to call
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# refresh passing in the view object.
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#
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# Notice this method raises an error if the template to be refreshed does not have a
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# virtual path set (true just for inline templates).
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def refresh(view)
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raise "A template needs to have a virtual path in order to be refreshed" unless @virtual_path
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lookup = view.lookup_context
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pieces = @virtual_path.split("/")
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name = pieces.pop
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partial = !!name.sub!(/^_/, "")
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lookup.disable_cache do
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lookup.find_template(name, [ pieces.join("/") ], partial, @locals)
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end
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end
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def inspect
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@inspect ||= defined?(Rails.root) ? identifier.sub("#{Rails.root}/", "".freeze) : identifier
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end
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# This method is responsible for properly setting the encoding of the
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# source. Until this point, we assume that the source is BINARY data.
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# If no additional information is supplied, we assume the encoding is
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# the same as <tt>Encoding.default_external</tt>.
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#
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# The user can also specify the encoding via a comment on the first
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# line of the template (# encoding: NAME-OF-ENCODING). This will work
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# with any template engine, as we process out the encoding comment
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# before passing the source on to the template engine, leaving a
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# blank line in its stead.
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def encode!
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return unless source.encoding == Encoding::BINARY
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# Look for # encoding: *. If we find one, we'll encode the
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# String in that encoding, otherwise, we'll use the
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# default external encoding.
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if source.sub!(/\A#{ENCODING_FLAG}/, "")
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encoding = magic_encoding = $1
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else
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encoding = Encoding.default_external
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end
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# Tag the source with the default external encoding
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# or the encoding specified in the file
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source.force_encoding(encoding)
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# If the user didn't specify an encoding, and the handler
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# handles encodings, we simply pass the String as is to
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# the handler (with the default_external tag)
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if !magic_encoding && @handler.respond_to?(:handles_encoding?) && @handler.handles_encoding?
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source
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# Otherwise, if the String is valid in the encoding,
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# encode immediately to default_internal. This means
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# that if a handler doesn't handle encodings, it will
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# always get Strings in the default_internal
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elsif source.valid_encoding?
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source.encode!
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# Otherwise, since the String is invalid in the encoding
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# specified, raise an exception
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else
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raise WrongEncodingError.new(source, encoding)
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end
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end
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private
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# Compile a template. This method ensures a template is compiled
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# just once and removes the source after it is compiled.
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def compile!(view)
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return if @compiled
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# Templates can be used concurrently in threaded environments
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# so compilation and any instance variable modification must
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# be synchronized
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@compile_mutex.synchronize do
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# Any thread holding this lock will be compiling the template needed
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# by the threads waiting. So re-check the @compiled flag to avoid
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# re-compilation
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return if @compiled
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if view.is_a?(ActionView::CompiledTemplates)
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mod = ActionView::CompiledTemplates
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else
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mod = view.singleton_class
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end
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instrument("!compile_template") do
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compile(mod)
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end
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# Just discard the source if we have a virtual path. This
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# means we can get the template back.
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@source = nil if @virtual_path
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@compiled = true
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end
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end
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# Among other things, this method is responsible for properly setting
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# the encoding of the compiled template.
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#
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# If the template engine handles encodings, we send the encoded
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# String to the engine without further processing. This allows
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# the template engine to support additional mechanisms for
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# specifying the encoding. For instance, ERB supports <%# encoding: %>
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#
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# Otherwise, after we figure out the correct encoding, we then
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# encode the source into <tt>Encoding.default_internal</tt>.
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# In general, this means that templates will be UTF-8 inside of Rails,
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# regardless of the original source encoding.
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def compile(mod)
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encode!
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code = @handler.call(self)
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# Make sure that the resulting String to be eval'd is in the
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# encoding of the code
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source = <<-end_src
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def #{method_name}(local_assigns, output_buffer)
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_old_virtual_path, @virtual_path = @virtual_path, #{@virtual_path.inspect};_old_output_buffer = @output_buffer;#{locals_code};#{code}
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ensure
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@virtual_path, @output_buffer = _old_virtual_path, _old_output_buffer
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end
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end_src
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# Make sure the source is in the encoding of the returned code
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source.force_encoding(code.encoding)
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# In case we get back a String from a handler that is not in
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# BINARY or the default_internal, encode it to the default_internal
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source.encode!
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# Now, validate that the source we got back from the template
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# handler is valid in the default_internal. This is for handlers
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# that handle encoding but screw up
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unless source.valid_encoding?
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raise WrongEncodingError.new(@source, Encoding.default_internal)
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end
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mod.module_eval(source, identifier, 0)
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ObjectSpace.define_finalizer(self, Finalizer[method_name, mod])
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end
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def handle_render_error(view, e)
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if e.is_a?(Template::Error)
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e.sub_template_of(self)
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raise e
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else
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template = self
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unless template.source
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template = refresh(view)
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template.encode!
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end
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raise Template::Error.new(template)
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end
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end
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def locals_code
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# Only locals with valid variable names get set directly. Others will
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# still be available in local_assigns.
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locals = @locals - Module::RUBY_RESERVED_KEYWORDS
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locals = locals.grep(/\A@?(?![A-Z0-9])(?:[[:alnum:]_]|[^\0-\177])+\z/)
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# Double assign to suppress the dreaded 'assigned but unused variable' warning
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locals.each_with_object("") { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
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end
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def method_name
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@method_name ||= begin
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m = "_#{identifier_method_name}__#{@identifier.hash}_#{__id__}"
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m.tr!("-".freeze, "_".freeze)
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m
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end
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end
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def identifier_method_name
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inspect.tr("^a-z_".freeze, "_".freeze)
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end
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def instrument(action, &block) # :doc:
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ActiveSupport::Notifications.instrument("#{action}.action_view", instrument_payload, &block)
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end
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def instrument_render_template(&block)
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ActiveSupport::Notifications.instrument("!render_template.action_view".freeze, instrument_payload, &block)
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end
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def instrument_payload
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{ virtual_path: @virtual_path, identifier: @identifier }
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end
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end
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end
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