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