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|
# frozen_string_literal: true
module Liquid
# Container for liquid nodes which conveniently wraps decision making logic
#
# Example:
#
# c = Condition.new(1, '==', 1)
# c.evaluate #=> true
#
class Condition # :nodoc:
@@operators = {
'==' => ->(cond, left, right) { cond.send(:equal_variables, left, right) },
'!=' => ->(cond, left, right) { !cond.send(:equal_variables, left, right) },
'<>' => ->(cond, left, right) { !cond.send(:equal_variables, left, right) },
'<' => :<,
'>' => :>,
'>=' => :>=,
'<=' => :<=,
'contains' => lambda do |_cond, left, right|
if left && right && left.respond_to?(:include?)
right = right.to_s if left.is_a?(String)
left.include?(right)
else
false
end
end,
}
class MethodLiteral
attr_reader :method_name, :to_s
def initialize(method_name, to_s)
@method_name = method_name
@to_s = to_s
end
end
@@method_literals = {
'blank' => MethodLiteral.new(:blank?, '').freeze,
'empty' => MethodLiteral.new(:empty?, '').freeze,
}
def self.operators
@@operators
end
def self.parse_expression(parse_context, markup)
@@method_literals[markup] || parse_context.parse_expression(markup)
end
attr_reader :attachment, :child_condition
attr_accessor :left, :operator, :right
def initialize(left = nil, operator = nil, right = nil)
@left = left
@operator = operator
@right = right
@child_relation = nil
@child_condition = nil
end
def evaluate(context = deprecated_default_context)
condition = self
result = nil
loop do
result = interpret_condition(condition.left, condition.right, condition.operator, context)
case condition.child_relation
when :or
break if result
when :and
break unless result
else
break
end
condition = condition.child_condition
end
result
end
def or(condition)
@child_relation = :or
@child_condition = condition
end
def and(condition)
@child_relation = :and
@child_condition = condition
end
def attach(attachment)
@attachment = attachment
end
def else?
false
end
def inspect
"#<Condition #{[@left, @operator, @right].compact.join(' ')}>"
end
protected
attr_reader :child_relation
private
def equal_variables(left, right)
if left.is_a?(MethodLiteral)
if right.respond_to?(left.method_name)
return right.send(left.method_name)
else
return nil
end
end
if right.is_a?(MethodLiteral)
if left.respond_to?(right.method_name)
return left.send(right.method_name)
else
return nil
end
end
left == right
end
def interpret_condition(left, right, op, context)
# If the operator is empty this means that the decision statement is just
# a single variable. We can just poll this variable from the context and
# return this as the result.
return context.evaluate(left) if op.nil?
left = Liquid::Utils.to_liquid_value(context.evaluate(left))
right = Liquid::Utils.to_liquid_value(context.evaluate(right))
operation = self.class.operators[op] || raise(Liquid::ArgumentError, "Unknown operator #{op}")
if operation.respond_to?(:call)
operation.call(self, left, right)
elsif left.respond_to?(operation) && right.respond_to?(operation) && !left.is_a?(Hash) && !right.is_a?(Hash)
begin
left.send(operation, right)
rescue ::ArgumentError => e
raise Liquid::ArgumentError, e.message
end
end
end
def deprecated_default_context
warn("DEPRECATION WARNING: Condition#evaluate without a context argument is deprecated" \
" and will be removed from Liquid 6.0.0.")
Context.new
end
class ParseTreeVisitor < Liquid::ParseTreeVisitor
def children
[
@node.left, @node.right,
@node.child_condition, @node.attachment
].compact
end
end
end
class ElseCondition < Condition
def else?
true
end
def evaluate(_context)
true
end
end
end
|
