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require "naught/null_class_builder/command"
require "naught/call_location"
require "naught/chain_proxy"
module Naught
class NullClassBuilder
module Commands
# Records method calls made on null objects for debugging
#
# When enabled, each null object instance tracks all method calls made to it,
# including the method name, arguments, and source location. Calls are grouped
# into "traces" - each time a method is called directly on the original null
# object (rather than on a chained result), a new trace begins.
#
# This uses lightweight proxy objects for chaining so that we can distinguish
# between `null.foo.bar` (one trace with two calls) and `null.foo; null.bar`
# (two traces with one call each).
#
# @example Basic usage
# NullObject = Naught.build do |config|
# config.callstack
# end
#
# null = NullObject.new
# null.foo(1, 2).bar
# null.baz
#
# null.__call_trace__
# # => [
# # [#<Naught::CallLocation foo(1, 2) at example.rb:8>,
# # #<Naught::CallLocation bar() at example.rb:8>],
# # [#<Naught::CallLocation baz() at example.rb:9>]
# # ]
#
# @api private
class Callstack < Command
# Install the callstack tracking mechanism
# @return [void]
# @api private
def call
install_call_trace_accessor
install_method_missing_tracking
install_chain_proxy_class
end
private
# Install the __call_trace__ accessor on null objects
# @return [void]
# @api private
def install_call_trace_accessor
defer_prepend_module do
attr_reader :__call_trace__
define_method(:initialize) do |*args, **kwargs|
super(*args, **kwargs)
@__call_trace__ = [] #: Array[Array[Naught::CallLocation]]
end
end
end
# Install method_missing override that records calls
# @return [void]
# @api private
def install_method_missing_tracking
defer_prepend_module do
define_method(:respond_to?) do |method_name, include_private = false|
method_name == :__call_trace__ || super(method_name, include_private)
end
define_method(:method_missing) do |method_name, *args, &block|
location = Naught::CallLocation.from_caller(method_name, args, Kernel.caller(1, 1).first)
@__call_trace__ ||= [] #: Array[Array[Naught::CallLocation]]
@__call_trace__ << [location]
Naught::ChainProxy.new(self, @__call_trace__.last)
end
end
end
# Install the ChainProxy class constant for backwards compatibility
# @return [void]
# @api private
def install_chain_proxy_class
defer_class { |null_class| null_class.const_set(:ChainProxy, Naught::ChainProxy) }
end
end
end
end
end
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