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# frozen_string_literal: true
module MemoWise
class InternalAPI
# Create initial mutable state to store memoized values if it doesn't
# already exist
#
# @param [Object] obj
# Object in which to create mutable state to store future memoized values
#
# @return [Object] the passed-in obj
def self.create_memo_wise_state!(obj)
# `@_memo_wise` stores memoized results of method calls in a hash keyed on
# method name. The structure is slightly different for different types of
# methods. It looks like:
# {
# zero_arg_method_name: :memoized_result,
# single_arg_method_name: { arg1 => :memoized_result, ... },
#
# # Surprisingly, this is faster than a single top-level hash key of: [:multi_arg_method_name, arg1, arg2]
# multi_arg_method_name: { [arg1, arg2] => :memoized_result, ... }
# }
obj.instance_variable_set(:@_memo_wise, {}) unless obj.instance_variable_defined?(:@_memo_wise)
obj
end
NONE = :none
ONE_REQUIRED_POSITIONAL = :one_required_positional
ONE_REQUIRED_KEYWORD = :one_required_keyword
MULTIPLE_REQUIRED = :multiple_required
SPLAT = :splat
DOUBLE_SPLAT = :double_splat
SPLAT_AND_DOUBLE_SPLAT = :splat_and_double_splat
# @param method [UnboundMethod] a method to categorize based on the types of
# arguments it has
# @return [Symbol] one of:
# - :none (example: `def foo`)
# - :one_required_positional (example: `def foo(a)`)
# - :one_required_keyword (example: `def foo(a:)`)
# - :multiple_required (examples: `def foo(a, b)`, `def foo(a:, b:)`, `def foo(a, b:)`)
# - :splat (examples: `def foo(a=1)`, `def foo(a, *b)`)
# - :double_splat (examples: `def foo(a: 1)`, `def foo(a:, **b)`)
# - :splat_and_double_splat (examples: `def foo(a=1, b: 2)`, `def foo(a=1, **b)`, `def foo(*a, **b)`)
def self.method_arguments(method)
return NONE if method.arity.zero?
parameters = method.parameters.map(&:first)
if parameters == [:req]
ONE_REQUIRED_POSITIONAL
elsif parameters == [:keyreq]
ONE_REQUIRED_KEYWORD
elsif parameters.all? { |type| type == :req || type == :keyreq }
MULTIPLE_REQUIRED
elsif parameters & %i[req opt rest] == parameters.uniq
SPLAT
elsif parameters & %i[keyreq key keyrest] == parameters.uniq
DOUBLE_SPLAT
else
SPLAT_AND_DOUBLE_SPLAT
end
end
# @param method [UnboundMethod] a method being memoized
# @return [String] the arguments string to use when defining our new
# memoized version of the method
def self.args_str(method)
case method_arguments(method)
when SPLAT then "*args"
when DOUBLE_SPLAT then "**kwargs"
when SPLAT_AND_DOUBLE_SPLAT then "*args, **kwargs"
when ONE_REQUIRED_POSITIONAL, ONE_REQUIRED_KEYWORD, MULTIPLE_REQUIRED
method.parameters.map do |type, name|
"#{name}#{':' if type == :keyreq}"
end.join(", ")
else
raise ArgumentError, "Unexpected arguments for #{method.name}"
end
end
# @param method [UnboundMethod] a method being memoized
# @return [String] the arguments string to use when calling the original
# method in our new memoized version of the method, i.e. when setting a
# memoized value
def self.call_str(method)
case method_arguments(method)
when SPLAT then "*args"
when DOUBLE_SPLAT then "**kwargs"
when SPLAT_AND_DOUBLE_SPLAT then "*args, **kwargs"
when ONE_REQUIRED_POSITIONAL, ONE_REQUIRED_KEYWORD, MULTIPLE_REQUIRED
method.parameters.map do |type, name|
type == :req ? name : "#{name}: #{name}"
end.join(", ")
else
raise ArgumentError, "Unexpected arguments for #{method.name}"
end
end
# @param method [UnboundMethod] a method being memoized
# @return [String] the string to use as a hash key when looking up a
# memoized value, based on the method's arguments
def self.key_str(method)
case method_arguments(method)
when SPLAT then "args"
when DOUBLE_SPLAT then "kwargs"
when SPLAT_AND_DOUBLE_SPLAT then "[args, kwargs]"
when MULTIPLE_REQUIRED then "[#{method.parameters.map(&:last).join(', ')}]"
else
raise ArgumentError, "Unexpected arguments for #{method.name}"
end
end
# Find the original class for which the given class is the corresponding
# "singleton class".
#
# See https://stackoverflow.com/questions/54531270/retrieve-a-ruby-object-from-its-singleton-class
#
# @param klass [Class]
# Singleton class to find the original class of
#
# @return Class
# Original class for which `klass` is the singleton class.
#
# @raise ArgumentError
# Raises if `klass` is not a singleton class.
#
def self.original_class_from_singleton(klass)
raise ArgumentError, "Must be a singleton class: #{klass.inspect}" unless klass.singleton_class?
# Since we call this method a lot, we memoize the results. This can have a
# huge impact; for example, in our test suite this drops our test times
# from over five minutes to just a few seconds.
@original_class_from_singleton ||= {}
# Search ObjectSpace
# * 1:1 relationship of singleton class to original class is documented
# * Performance concern: searches all Class objects
# But, only runs at load time and results are memoized
@original_class_from_singleton[klass] ||= ObjectSpace.each_object(Module).find do |cls|
cls.singleton_class == klass
end
end
# Convention we use for renaming the original method when we replace with
# the memoized version in {MemoWise.memo_wise}.
#
# @param method_name [Symbol]
# Name for which to return the renaming for the original method
#
# @return [Symbol]
# Renamed method to use for the original method with name `method_name`
#
def self.original_memo_wised_name(method_name)
:"_memo_wise_original_#{method_name}"
end
# Returns visibility of an instance method defined on class `target`.
#
# @param target [Class, Module]
# The class to which we are prepending MemoWise to provide memoization.
#
# @param method_name [Symbol]
# Name of existing *instance* method find the visibility of.
#
# @return [:private, :protected, :public]
# Visibility of existing instance method of the class.
#
# @raise ArgumentError
# Raises `ArgumentError` unless `method_name` is a `Symbol` corresponding
# to an existing **instance** method defined on `klass`.
#
def self.method_visibility(target, method_name)
if target.private_method_defined?(method_name)
:private
elsif target.protected_method_defined?(method_name)
:protected
elsif target.public_method_defined?(method_name)
:public
else
raise ArgumentError, "#{method_name.inspect} must be a method on #{target}"
end
end
# Validates that {.memo_wise} has already been called on `method_name`.
#
# @param target [Class, Module]
# The class to which we are prepending MemoWise to provide memoization.
#
# @param method_name [Symbol]
# Name of method to validate has already been setup with {.memo_wise}
def self.validate_memo_wised!(target, method_name)
original_name = original_memo_wised_name(method_name)
unless target_class(target).private_method_defined?(original_name)
raise ArgumentError, "#{method_name} is not a memo_wised method"
end
end
# @param target [Class, Module]
# The class to which we are prepending MemoWise to provide memoization.
# @return [Class] where we look for method definitions
def self.target_class(target)
if target.instance_of?(Class)
# A class's methods are defined in its singleton class
target.singleton_class
else
# An object's methods are defined in its class
target.class
end
end
private_class_method :target_class
end
end
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