Class: ActionView::Template

Relationships & Source Files
Namespace Children
Modules: `Handlers`, `Sources`
Classes: `HTML`, `Inline`, `RawFile`, `Renderable`, `SimpleType`, `Text`
Exceptions: `Error`
Extension / Inclusion / Inheritance Descendants
Subclasses: Inline
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, `Handlers`, `::ActiveSupport::Autoload`
Inherits:	Object
Defined in:	actionview/lib/action_view/template.rb, actionview/lib/action_view/template/error.rb, actionview/lib/action_view/template/handlers.rb, actionview/lib/action_view/template/html.rb, actionview/lib/action_view/template/inline.rb, actionview/lib/action_view/template/raw_file.rb, actionview/lib/action_view/template/renderable.rb, actionview/lib/action_view/template/sources.rb, actionview/lib/action_view/template/text.rb, actionview/lib/action_view/template/types.rb, actionview/lib/action_view/template/handlers/erb.rb, actionview/lib/action_view/template/handlers/erb/erubi.rb, actionview/lib/action_view/template/sources/file.rb

Constant Summary

LEADING_ENCODING_REGEXP = private
# File 'actionview/lib/action_view/template.rb', line 308
```
/\A#{ENCODING_FLAG}/
```
NONE =
# File 'actionview/lib/action_view/template.rb', line 197
```
Object.new
```
RUBY_RESERVED_KEYWORDS = private
# File 'actionview/lib/action_view/template.rb', line 558
```
::ActiveSupport::Delegation::RUBY_RESERVED_KEYWORDS
```
STRICT_LOCALS_REGEX =
# File 'actionview/lib/action_view/template.rb', line 10
```
/\#\slocals:\s\((.*)\)/
```
Types = Internal use only
# File 'actionview/lib/action_view/template/types.rb', line 48
```
SimpleType
```

Class Attribute Summary

.mime_types_implementation=(implementation) writeonly

Class Method Summary

.new(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil) ⇒ Template constructor

`Handlers` - Extended

handler_for_extension, register_default_template_handler,
register_template_handler	Register an object that knows how to handle template files with the given extensions.
registered_template_handler, template_handler_extensions,
unregister_template_handler	Opposite to register_template_handler.

`::ActiveSupport::Autoload` - Extended

autoload, autoload_at, autoload_under, eager_autoload, eager_load!

Instance Attribute Summary

#format readonly
#frozen_string_literal rw
#handler readonly
#identifier readonly
#strict_locals? ⇒ Boolean readonly

Returns whether a template is using strict locals.
#supports_streaming? ⇒ Boolean readonly

Returns whether the underlying handler supports streaming.
#variable readonly
#variant readonly
#virtual_path readonly

Instance Method Summary

#encode!

This method is responsible for properly setting the encoding of the source.
#inspect
#local_assigns

Returns a hash with the defined local variables.
#locals

The locals this template has been or will be compiled for, or nil if this is a strict locals template.
#render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block)

Render a template.
#short_identifier
#source
#strict_locals!

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.
#translate_location(backtrace_location, spot)

Translate an error location returned by ErrorHighlight to the correct source location inside the template.
#type
#compile(mod) private

Among other things, this method is responsible for properly setting the encoding of the compiled template.
#compile!(view) private

Compile a template.
#compiled_source private

This method compiles the source of the template.
#find_node_by_id(node, node_id) private
#handle_render_error(view, e) private
#identifier_method_name private
#instrument(action, &block) private
#instrument_payload private
#instrument_render_template(&block) private
#locals_code private
#offset private
#marshal_dump Internal use only

Exceptions are marshalled when using the parallel test runner with DRb, so we need to ensure that references to the template object can be marshalled as well.
#marshal_load(array) Internal use only
#method_name Internal use only
#spot(location) Internal use only

Constructor Details

.new(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil) ⇒ `Template`

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 199


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

Class Attribute Details

.mime_types_implementation=(implementation) (writeonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 184


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

Instance Attribute Details

#format (readonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 195


attr_reader :variable, :format, :variant, :virtual_path

#frozen_string_literal (rw)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 180


singleton_class.attr_accessor :frozen_string_literal

#handler (readonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 194


attr_reader :identifier, :handler

#identifier (readonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 194


attr_reader :identifier, :handler

#strict_locals? ⇒ `Boolean` (readonly)

Returns whether a template is using strict locals.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 380


def strict_locals?
  strict_locals!
end

#supports_streaming? ⇒ `Boolean` (readonly)

Returns whether the underlying handler supports streaming. If so, a streaming buffer may be passed when it starts rendering.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 261


def supports_streaming?
  handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
end

#variable (readonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 195


attr_reader :variable, :format, :variant, :virtual_path

#variant (readonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 195


attr_reader :variable, :format, :variant, :virtual_path

#virtual_path (readonly)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 195


attr_reader :variable, :format, :variant, :virtual_path

Instance Method Details

#compile(mod) (private)

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.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 500


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
  parameters -= [[:req, :local_assigns], [: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

  non_kwarg_parameters.pop if non_kwarg_parameters.last == %i(block _)

  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!(view) (private)

Compile a template. This method ensures a template is compiled just once and removes the source after it is compiled.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 418


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

#compiled_source (private)

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.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 443


def compiled_source
  set_strict_locals = strict_locals!
  source = encode!
  code = @handler.call(self, source)

  method_arguments =
    if set_strict_locals
      if set_strict_locals.include?("&")
        "local_assigns, output_buffer, #{set_strict_locals}"
      else
        "local_assigns, output_buffer, #{set_strict_locals}, &_"
      end
    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

#encode!

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.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 321


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

#find_node_by_id(node, node_id) (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 405


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

#handle_render_error(view, e) (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 549


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

#identifier_method_name (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 574


def identifier_method_name
  short_identifier.tr("^a-z_", "_")
end

#inspect

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 300


def inspect
  "#<#{self.class.name} #{short_identifier} locals=#{locals.inspect}>"
end

#instrument(action, &block) (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 578


def instrument(action, &block) # :doc:
  ActiveSupport::Notifications.instrument("#{action}.action_view", instrument_payload, &block)
end

#instrument_payload (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 586


def instrument_payload
  { virtual_path: @virtual_path, identifier: @identifier }
end

#instrument_render_template(&block) (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 582


def instrument_render_template(&block)
  ActiveSupport::Notifications.instrument("!render_template.action_view", instrument_payload, &block)
end

#local_assigns

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 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 %>

By default, templates will accept any #locals as keyword arguments and make them available to local_assigns. To restrict what local_assigns a template will accept, add a locals: magic comment:

<%# locals: (headline:, alerts: []) %>

<h1><%= headline %></h1>

<% alerts.each do |alert| %>
  <p><%= alert %></p>
<% end %>

Read more about strict locals in Action View Overview in the guides.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 166


rdoc_method :method: local_assigns

#locals

The locals this template has been or will be compiled for, or nil if this is a strict locals template.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 223


def locals
  if strict_locals?
    nil
  else
    @locals
  end
end

#locals_code (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 561


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 - 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

#marshal_dump

This method is for internal use only.

Exceptions are marshalled when using the parallel test runner with DRb, so we need to ensure that references to the template object can be marshalled as well. This means forgoing the marshalling of the compiler mutex and instantiating that again on unmarshalling.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 387


def marshal_dump # :nodoc:
  [ @source, @identifier, @handler, @compiled, @locals, @virtual_path, @format, @variant ]
end

#marshal_load(array)

This method is for internal use only.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 391


def marshal_load(array) # :nodoc:
  @source, @identifier, @handler, @compiled, @locals, @virtual_path, @format, @variant = *array
  @compile_mutex = Mutex.new
end

#method_name

This method is for internal use only.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 396


def method_name # :nodoc:
  @method_name ||= begin
    m = +"_#{identifier_method_name}__#{@identifier.hash}_#{__id__}"
    m.tr!("-", "_")
    m
  end
end

#offset (private)

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 541


def offset
  if Template.frozen_string_literal
    -1
  else
    0
  end
end

#render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block)

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.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 271


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
      result = view._run(method_name, self, locals, OutputBuffer.new, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)
      result.is_a?(OutputBuffer) ? result.to_s : result
    end
  end
rescue => e
  handle_render_error(view, e)
end

#short_identifier

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 296


def short_identifier
  @short_identifier ||= defined?(Rails.root) ? identifier.delete_prefix("#{Rails.root}/") : identifier
end

#source

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 304


def source
  @source.to_s
end

#spot(location)

This method is for internal use only.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 231


def spot(location) # :nodoc:
  node_id = RubyVM::AbstractSyntaxTree.node_id_for_backtrace_location(location)
  found =
    if RubyVM::InstructionSequence.compile("").to_a[4][:parser] == :prism
      require "prism"

      if Prism::VERSION >= "1.0.0"
        result = Prism.parse(compiled_source).value
        result.breadth_first_search { |node| node.node_id == node_id }
      end
    else
      node = RubyVM::AbstractSyntaxTree.parse(compiled_source, keep_script_lines: true)
      find_node_by_id(node, node_id)
    end

  ErrorHighlight.spot(found) if found
end

#strict_locals!

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 accepts 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.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 366


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

#translate_location(backtrace_location, spot)

Translate an error location returned by ErrorHighlight to the correct source location inside the template.

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 251


def translate_location(backtrace_location, spot)
  if handler.respond_to?(:translate_location)
    handler.translate_location(spot, backtrace_location, encode!) || spot
  else
    spot
  end
end

#type

[ GitHub ]

# File 'actionview/lib/action_view/template.rb', line 292


def type
  @type ||= Types[format]
end

Class: ActionView::Template

Constant Summary

Class Attribute Summary

Class Method Summary

Handlers - Extended

::ActiveSupport::Autoload - Extended

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil) ⇒ Template

Class Attribute Details

.mime_types_implementation=(implementation) (writeonly)

Instance Attribute Details

#format (readonly)

#frozen_string_literal (rw)

#handler (readonly)

#identifier (readonly)

#strict_locals? ⇒ Boolean (readonly)

#supports_streaming? ⇒ Boolean (readonly)

#variable (readonly)

#variant (readonly)

#virtual_path (readonly)

Instance Method Details

#compile(mod) (private)

#compile!(view) (private)

#compiled_source (private)

#encode!

#find_node_by_id(node, node_id) (private)

#handle_render_error(view, e) (private)

#identifier_method_name (private)

#inspect

#instrument(action, &block) (private)

#instrument_payload (private)

#instrument_render_template(&block) (private)

#local_assigns

#locals

#locals_code (private)

#marshal_dump

#marshal_load(array)

#method_name

#offset (private)

#render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block)

#short_identifier

#source

#spot(location)

#strict_locals!

#translate_location(backtrace_location, spot)

#type

`Handlers` - Extended

`::ActiveSupport::Autoload` - Extended

.new(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil) ⇒ `Template`

#strict_locals? ⇒ `Boolean` (readonly)

#supports_streaming? ⇒ `Boolean` (readonly)