class ActionView::Template
Action View Template¶ ↑
Constants
- LEADING_ENCODING_REGEXP
- NONE
- STRICT_LOCALS_REGEX
Attributes
Public Class Methods
# File lib/action_view/template.rb, line 171 def mime_types_implementation=(implementation) # This method isn't thread-safe, but it's not supposed # to be called after initialization if self::Types != implementation remove_const(:Types) const_set(:Types, implementation) end end
# File lib/action_view/template.rb, line 186 def initialize(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil) @source = source.dup @identifier = identifier @handler = handler @compiled = false @locals = locals @virtual_path = virtual_path @variable = if @virtual_path base = @virtual_path.end_with?("/") ? "" : ::File.basename(@virtual_path) base =~ /\A_?(.*?)(?:\.\w+)*\z/ $1.to_sym end @format = format @variant = variant @compile_mutex = Mutex.new @strict_locals = NONE @strict_local_keys = nil @type = nil end
Public Instance Methods
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.
# File lib/action_view/template.rb, line 297 def encode! source = self.source return source 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!(LEADING_ENCODING_REGEXP, "") 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
# File lib/action_view/template.rb, line 276 def inspect "#<#{self.class.name} #{short_identifier} locals=#{locals.inspect}>" end
Returns a hash with the defined local variables.
Given this sub template rendering:
<%= render "application/header", { headline: "Welcome", person: person } %>
You can use local_assigns
in the sub templates to access the local variables:
local_assigns[:headline] # => "Welcome"
Each key in local_assigns
is available as a partial-local variable:
local_assigns[:headline] # => "Welcome" headline # => "Welcome"
Since local_assigns
is a Hash
, it’s compatible with Ruby 3.1’s pattern matching assignment operator:
local_assigns => { headline:, **options } headline # => "Welcome" options # => {}
Pattern matching assignment also supports variable renaming:
local_assigns => { headline: title } title # => "Welcome"
If a template refers to a variable that isn’t passed into the view as part of the locals: { ... }
Hash, the template will raise an ActionView::Template::Error
:
<%# => raises ActionView::Template::Error %> <% alerts.each do |alert| %> <p><%= alert %></p> <% end %>
Since local_assigns
returns a Hash
instance, you can conditionally read a variable, then fall back to a default value when the key isn’t part of the locals: { ... }
options:
<% local_assigns.fetch(:alerts, []).each do |alert| %> <p><%= alert %></p> <% end %>
Combining Ruby 3.1’s pattern matching assignment with calls to +Hash#with_defaults+ enables compact partial-local variable assignments:
<% local_assigns.with_defaults(alerts: []) => { headline:, alerts: } %> <h1><%= headline %></h1> <% alerts.each do |alert| %> <p><%= alert %></p> <% end %>
# File lib/action_view/template.rb, line 152 eager_autoload do autoload :Error autoload :RawFile autoload :Renderable autoload :Handlers autoload :HTML autoload :Inline autoload :Types autoload :Sources autoload :Text autoload :Types end
The locals this template has been or will be compiled for, or nil if this is a strict locals template.
# File lib/action_view/template.rb, line 210 def locals if strict_locals? nil else @locals end 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.
# File lib/action_view/template.rb, line 248 def render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block) instrument_render_template do compile!(view) if strict_locals? && @strict_local_keys && !implicit_locals.empty? locals_to_ignore = implicit_locals - @strict_local_keys locals.except!(*locals_to_ignore) end if buffer view._run(method_name, self, locals, buffer, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block) nil else view._run(method_name, self, locals, OutputBuffer.new, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)&.to_s end end rescue => e handle_render_error(view, e) end
# File lib/action_view/template.rb, line 272 def short_identifier @short_identifier ||= defined?(Rails.root) ? identifier.delete_prefix("#{Rails.root}/") : identifier end
# File lib/action_view/template.rb, line 280 def source @source.to_s end
This method is responsible for marking a template as having strict locals which means the template can only accept the locals defined in a magic comment. For example, if your template acceps the locals title
and comment_count
, add the following to your template file:
<%# locals: (title: "Default title", comment_count: 0) %>
Strict locals are useful for validating template arguments and for specifying defaults.
# File lib/action_view/template.rb, line 342 def strict_locals! if @strict_locals == NONE self.source.sub!(STRICT_LOCALS_REGEX, "") @strict_locals = $1 return if @strict_locals.nil? # Magic comment not found @strict_locals = "**nil" if @strict_locals.blank? end @strict_locals end
Returns whether a template is using strict locals.
# File lib/action_view/template.rb, line 356 def strict_locals? strict_locals! end
Returns whether the underlying handler supports streaming. If so, a streaming buffer may be passed when it starts rendering.
# File lib/action_view/template.rb, line 238 def supports_streaming? handler.respond_to?(:supports_streaming?) && handler.supports_streaming? end
Translate an error location returned by ErrorHighlight to the correct source location inside the template.
# File lib/action_view/template.rb, line 228 def translate_location(backtrace_location, spot) if handler.respond_to?(:translate_location) handler.translate_location(spot, backtrace_location, encode!) || spot else spot end end
# File lib/action_view/template.rb, line 268 def type @type ||= Types[format] end
Private Instance Methods
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 Encoding.default_internal
. In general, this means that templates will be UTF-8 inside of Rails, regardless of the original source encoding.
# File lib/action_view/template.rb, line 472 def compile(mod) begin mod.module_eval(compiled_source, identifier, offset) rescue SyntaxError # Account for when code in the template is not syntactically valid; e.g. if we're using # ERB and the user writes <%= foo( %>, attempting to call a helper `foo` and interpolate # the result into the template, but missing an end parenthesis. raise SyntaxErrorInTemplate.new(self, encode!) end return unless strict_locals? parameters = mod.instance_method(method_name).parameters - [[:req, :output_buffer]] # Check compiled method parameters to ensure that only kwargs # were provided as strict locals, preventing `locals: (foo, *foo)` etc # and allowing `locals: (foo:)`. non_kwarg_parameters = parameters.select do |parameter| ![:keyreq, :key, :keyrest, :nokey].include?(parameter[0]) end unless non_kwarg_parameters.empty? mod.undef_method(method_name) raise ArgumentError.new( "#{non_kwarg_parameters.map { |_, name| "`#{name}`" }.to_sentence} set as non-keyword " \ "#{'argument'.pluralize(non_kwarg_parameters.length)} for #{short_identifier}. " \ "Locals can only be set as keyword arguments." ) end unless parameters.any? { |type, _| type == :keyrest } parameters.map!(&:last) parameters.sort! @strict_local_keys = parameters.freeze end end
Compile a template. This method ensures a template is compiled just once and removes the source after it is compiled.
# File lib/action_view/template.rb, line 394 def compile!(view) 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 mod = view.compiled_method_container instrument("!compile_template") do compile(mod) end @compiled = true end end
This method compiles the source of the template. The compilation of templates involves setting strict_locals! if applicable, encoding the template, and setting frozen string literal.
# File lib/action_view/template.rb, line 419 def compiled_source set_strict_locals = strict_locals! source = encode! code = @handler.call(self, source) method_arguments = if set_strict_locals "output_buffer, #{set_strict_locals}" else "local_assigns, output_buffer" end # Make sure that the resulting String to be eval'd is in the # encoding of the code source = +<<-end_src def #{method_name}(#{method_arguments}) @virtual_path = #{@virtual_path.inspect};#{locals_code};#{code} 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 if Template.frozen_string_literal "# frozen_string_literal: true\n#{source}" else source end end
# File lib/action_view/template.rb, line 381 def find_node_by_id(node, node_id) return node if node.node_id == node_id node.children.grep(node.class).each do |child| found = find_node_by_id(child, node_id) return found if found end false end
# File lib/action_view/template.rb, line 518 def handle_render_error(view, e) if e.is_a?(Template::Error) e.sub_template_of(self) raise e else raise Template::Error.new(self) end end
# File lib/action_view/template.rb, line 540 def identifier_method_name short_identifier.tr("^a-z_", "_") end
# File lib/action_view/template.rb, line 544 def instrument(action, &block) # :doc: ActiveSupport::Notifications.instrument("#{action}.action_view", instrument_payload, &block) end
# File lib/action_view/template.rb, line 552 def instrument_payload { virtual_path: @virtual_path, identifier: @identifier } end
# File lib/action_view/template.rb, line 548 def instrument_render_template(&block) ActiveSupport::Notifications.instrument("!render_template.action_view", instrument_payload, &block) end
# File lib/action_view/template.rb, line 527 def locals_code return "" if strict_locals? # Only locals with valid variable names get set directly. Others will # still be available in local_assigns. locals = @locals - Module::RUBY_RESERVED_KEYWORDS locals = locals.grep(/\A(?![A-Z0-9])(?:[[:alnum:]_]|[^\0-\177])+\z/) # Assign for the same variable is to suppress unused variable warning locals.each_with_object(+"") { |key, code| code << "#{key} = local_assigns[:#{key}]; #{key} = #{key};" } end
# File lib/action_view/template.rb, line 510 def offset if Template.frozen_string_literal -1 else 0 end end