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module Liquid
# Context keeps the variable stack and resolves variables, as well as keywords
#
# context['variable'] = 'testing'
# context['variable'] #=> 'testing'
# context['true'] #=> true
# context['10.2232'] #=> 10.2232
#
# context.stack do
# context['bob'] = 'bobsen'
# end
#
# context['bob'] #=> nil class Context
class Context
attr_reader :scopes, :errors, :registers, :environments, :resource_limits
attr_accessor :exception_renderer, :template_name, :partial, :global_filter, :strict_variables, :strict_filters
def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = nil)
@environments = [environments].flatten
@scopes = [(outer_scope || {})]
@registers = registers
@errors = []
@partial = false
@strict_variables = false
@resource_limits = resource_limits || ResourceLimits.new(Template.default_resource_limits)
squash_instance_assigns_with_environments
@this_stack_used = false
self.exception_renderer = Template.default_exception_renderer
if rethrow_errors
self.exception_renderer = ->(e) { raise }
end
@interrupts = []
@filters = []
@global_filter = nil
end
def warnings
@warnings ||= []
end
def strainer
@strainer ||= Strainer.create(self, @filters)
end
# Adds filters to this context.
#
# Note that this does not register the filters with the main Template object. see <tt>Template.register_filter</tt>
# for that
def add_filters(filters)
filters = [filters].flatten.compact
@filters += filters
@strainer = nil
end
def apply_global_filter(obj)
global_filter.nil? ? obj : global_filter.call(obj)
end
# are there any not handled interrupts?
def interrupt?
!@interrupts.empty?
end
# push an interrupt to the stack. this interrupt is considered not handled.
def push_interrupt(e)
@interrupts.push(e)
end
# pop an interrupt from the stack
def pop_interrupt
@interrupts.pop
end
def handle_error(e, line_number = nil)
e = internal_error unless e.is_a?(Liquid::Error)
e.template_name ||= template_name
e.line_number ||= line_number
errors.push(e)
exception_renderer.call(e).to_s
end
def invoke(method, *args)
strainer.invoke(method, *args).to_liquid
end
# Push new local scope on the stack. use <tt>Context#stack</tt> instead
def push(new_scope = {})
@scopes.unshift(new_scope)
raise StackLevelError, "Nesting too deep".freeze if @scopes.length > Block::MAX_DEPTH
end
# Merge a hash of variables in the current local scope
def merge(new_scopes)
@scopes[0].merge!(new_scopes)
end
# Pop from the stack. use <tt>Context#stack</tt> instead
def pop
raise ContextError if @scopes.size == 1
@scopes.shift
end
# Pushes a new local scope on the stack, pops it at the end of the block
#
# Example:
# context.stack do
# context['var'] = 'hi'
# end
#
# context['var] #=> nil
def stack(new_scope = nil)
old_stack_used = @this_stack_used
if new_scope
push(new_scope)
@this_stack_used = true
else
@this_stack_used = false
end
yield
ensure
pop if @this_stack_used
@this_stack_used = old_stack_used
end
def clear_instance_assigns
@scopes[0] = {}
end
# Only allow String, Numeric, Hash, Array, Proc, Boolean or <tt>Liquid::Drop</tt>
def []=(key, value)
unless @this_stack_used
@this_stack_used = true
push({})
end
@scopes[0][key] = value
end
# Look up variable, either resolve directly after considering the name. We can directly handle
# Strings, digits, floats and booleans (true,false).
# If no match is made we lookup the variable in the current scope and
# later move up to the parent blocks to see if we can resolve the variable somewhere up the tree.
# Some special keywords return symbols. Those symbols are to be called on the rhs object in expressions
#
# Example:
# products == empty #=> products.empty?
def [](expression)
evaluate(Expression.parse(expression))
end
def key?(key)
self[key] != nil
end
def evaluate(object)
object.respond_to?(:evaluate) ? object.evaluate(self) : object
end
# Fetches an object starting at the local scope and then moving up the hierachy
def find_variable(key, raise_on_not_found: true)
# This was changed from find() to find_index() because this is a very hot
# path and find_index() is optimized in MRI to reduce object allocation
index = @scopes.find_index { |s| s.key?(key) }
scope = @scopes[index] if index
variable = nil
if scope.nil?
@environments.each do |e|
variable = lookup_and_evaluate(e, key, raise_on_not_found: raise_on_not_found)
# When lookup returned a value OR there is no value but the lookup also did not raise
# then it is the value we are looking for.
if !variable.nil? || @strict_variables && raise_on_not_found
scope = e
break
end
end
end
scope ||= @environments.last || @scopes.last
variable ||= lookup_and_evaluate(scope, key, raise_on_not_found: raise_on_not_found)
variable = variable.to_liquid
variable.context = self if variable.respond_to?(:context=)
variable
end
def lookup_and_evaluate(obj, key, raise_on_not_found: true)
if @strict_variables && raise_on_not_found && obj.respond_to?(:key?) && !obj.key?(key)
raise Liquid::UndefinedVariable, "undefined variable #{key}"
end
value = obj[key]
if value.is_a?(Proc) && obj.respond_to?(:[]=)
obj[key] = (value.arity == 0) ? value.call : value.call(self)
else
value
end
end
private
def internal_error
# raise and catch to set backtrace and cause on exception
raise Liquid::InternalError, 'internal'
rescue Liquid::InternalError => exc
exc
end
def squash_instance_assigns_with_environments
@scopes.last.each_key do |k|
@environments.each do |env|
if env.key?(k)
scopes.last[k] = lookup_and_evaluate(env, k)
break
end
end
end
end # squash_instance_assigns_with_environments
end # Context
end # Liquid
|
