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module Tilt
TOPOBJECT = defined?(BasicObject) ? BasicObject : Object
# Base class for template implementations. Subclasses must implement
# the #prepare method and one of the #evaluate or #precompiled_template
# methods.
class Template
# Template source; loaded from a file or given directly.
attr_reader :data
# The name of the file where the template data was loaded from.
attr_reader :file
# The line number in #file where template data was loaded from.
attr_reader :line
# A Hash of template engine specific options. This is passed directly
# to the underlying engine and is not used by the generic template
# interface.
attr_reader :options
# Used to determine if this class's initialize_engine method has
# been called yet.
@engine_initialized = false
class << self
attr_accessor :engine_initialized
alias engine_initialized? engine_initialized
attr_accessor :default_mime_type
end
# Create a new template with the file, line, and options specified. By
# default, template data is read from the file. When a block is given,
# it should read template data and return as a String. When file is nil,
# a block is required.
#
# All arguments are optional.
def initialize(file=nil, line=1, options={}, &block)
@file, @line, @options = nil, 1, {}
[options, line, file].compact.each do |arg|
case
when arg.respond_to?(:to_str) ; @file = arg.to_str
when arg.respond_to?(:to_int) ; @line = arg.to_int
when arg.respond_to?(:to_hash) ; @options = arg.to_hash.dup
when arg.respond_to?(:path) ; @file = arg.path
else raise TypeError
end
end
raise ArgumentError, "file or block required" if (@file || block).nil?
# call the initialize_engine method if this is the very first time
# an instance of this class has been created.
if !self.class.engine_initialized?
initialize_engine
self.class.engine_initialized = true
end
# used to hold compiled template methods
@compiled_method = {}
# used on 1.9 to set the encoding if it is not set elsewhere (like a magic comment)
# currently only used if template compiles to ruby
@default_encoding = @options.delete :default_encoding
# load template data and prepare (uses binread to avoid encoding issues)
@reader = block || lambda { |t| File.respond_to?(:binread) ? File.binread(@file) : File.read(@file) }
@data = @reader.call(self)
prepare
end
# Render the template in the given scope with the locals specified. If a
# block is given, it is typically available within the template via
# +yield+.
def render(scope=Object.new, locals={}, &block)
evaluate scope, locals || {}, &block
end
# The basename of the template file.
def basename(suffix='')
File.basename(file, suffix) if file
end
# The template file's basename with all extensions chomped off.
def name
basename.split('.', 2).first if basename
end
# The filename used in backtraces to describe the template.
def eval_file
file || '(__TEMPLATE__)'
end
# Whether or not this template engine allows executing Ruby script
# within the template. If this is false, +scope+ and +locals+ will
# generally not be used, nor will the provided block be avaiable
# via +yield+.
# This should be overridden by template subclasses.
def allows_script?
true
end
protected
# Called once and only once for each template subclass the first time
# the template class is initialized. This should be used to require the
# underlying template library and perform any initial setup.
def initialize_engine
end
# Like Kernel#require but issues a warning urging a manual require when
# running under a threaded environment.
def require_template_library(name)
if Thread.list.size > 1
warn "WARN: tilt autoloading '#{name}' in a non thread-safe way; " +
"explicit require '#{name}' suggested."
end
require name
end
# Do whatever preparation is necessary to setup the underlying template
# engine. Called immediately after template data is loaded. Instance
# variables set in this method are available when #evaluate is called.
#
# Subclasses must provide an implementation of this method.
def prepare
if respond_to?(:compile!)
# backward compat with tilt < 0.6; just in case
warn 'Tilt::Template#compile! is deprecated; implement #prepare instead.'
compile!
else
raise NotImplementedError
end
end
# Execute the compiled template and return the result string. Template
# evaluation is guaranteed to be performed in the scope object with the
# locals specified and with support for yielding to the block.
#
# This method is only used by source generating templates. Subclasses that
# override render() may not support all features.
def evaluate(scope, locals, &block)
method = compiled_method(locals.keys)
method.bind(scope).call(locals, &block)
end
# Generates all template source by combining the preamble, template, and
# postamble and returns a two-tuple of the form: [source, offset], where
# source is the string containing (Ruby) source code for the template and
# offset is the integer line offset where line reporting should begin.
#
# Template subclasses may override this method when they need complete
# control over source generation or want to adjust the default line
# offset. In most cases, overriding the #precompiled_template method is
# easier and more appropriate.
def precompiled(locals)
preamble = precompiled_preamble(locals)
template = precompiled_template(locals)
magic_comment = extract_magic_comment(template)
if magic_comment
# Magic comment e.g. "# coding: utf-8" has to be in the first line.
# So we copy the magic comment to the first line.
preamble = magic_comment + "\n" + preamble
end
parts = [
preamble,
template,
precompiled_postamble(locals)
]
[parts.join("\n"), preamble.count("\n") + 1]
end
# A string containing the (Ruby) source code for the template. The
# default Template#evaluate implementation requires either this method
# or the #precompiled method be overridden. When defined, the base
# Template guarantees correct file/line handling, locals support, custom
# scopes, and support for template compilation when the scope object
# allows it.
def precompiled_template(locals)
raise NotImplementedError
end
# Generates preamble code for initializing template state, and performing
# locals assignment. The default implementation performs locals
# assignment only. Lines included in the preamble are subtracted from the
# source line offset, so adding code to the preamble does not effect line
# reporting in Kernel::caller and backtraces.
def precompiled_preamble(locals)
locals.map do |k,v|
if k.to_s =~ /\A[a-z_][a-zA-Z_0-9]*\z/
"#{k} = locals[#{k.inspect}]"
else
raise "invalid locals key: #{k.inspect} (keys must be variable names)"
end
end.join("\n")
end
# Generates postamble code for the precompiled template source. The
# string returned from this method is appended to the precompiled
# template source.
def precompiled_postamble(locals)
''
end
# The compiled method for the locals keys provided.
def compiled_method(locals_keys)
@compiled_method[locals_keys] ||=
compile_template_method(locals_keys)
end
private
def compile_template_method(locals)
source, offset = precompiled(locals)
method_name = "__tilt_#{Thread.current.object_id.abs}"
method_source = <<-RUBY
#{extract_magic_comment source}
TOPOBJECT.class_eval do
def #{method_name}(locals)
Thread.current[:tilt_vars] = [self, locals]
class << self
this, locals = Thread.current[:tilt_vars]
this.instance_eval do
RUBY
offset += method_source.count("\n")
method_source << source
method_source << "\nend;end;end;end"
Object.class_eval method_source, eval_file, line - offset
unbind_compiled_method(method_name)
end
def unbind_compiled_method(method_name)
method = TOPOBJECT.instance_method(method_name)
TOPOBJECT.class_eval { remove_method(method_name) }
method
end
def extract_magic_comment(script)
comment = script.slice(/\A[ \t]*\#.*coding\s*[=:]\s*([[:alnum:]\-_]+).*$/)
if comment && !%w[ascii-8bit binary].include?($1.downcase)
comment
elsif @default_encoding
"# coding: #{@default_encoding}"
end
end
end
end
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