b4558c10fb
Having collection caching that wraps templates and automatically tries to infer if they are cachable proved to be too much of a hassle. We'd rather have it be something you explicitly turn on. This removes much of the code and docs to explain the previous automatic behavior. This change also removes scoped cache keys and passing cache_options.
355 lines
13 KiB
Ruby
355 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>self.handles_encoding?</tt>
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# 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 start 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".freeze) 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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protected
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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) #:nodoc:
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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) #:nodoc:
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encode!
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method_name = self.method_name
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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) #:nodoc:
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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 #:nodoc:
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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 #:nodoc:
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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 #:nodoc:
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inspect.tr('^a-z_'.freeze, '_'.freeze)
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end
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def instrument(action, &block)
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payload = { virtual_path: @virtual_path, identifier: @identifier }
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case action
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when "!render_template".freeze
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ActiveSupport::Notifications.instrument("!render_template.action_view".freeze, payload, &block)
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else
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ActiveSupport::Notifications.instrument("#{action}.action_view".freeze, payload, &block)
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end
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end
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end
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end
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