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|
# frozen_string_literal: true
require 'dry/core/cache'
require 'dry/types/predicate_registry'
module Dry
module Types
# PredicateInferrer returns the list of predicates used by a type.
#
# @api public
class PredicateInferrer
extend Core::Cache
TYPE_TO_PREDICATE = {
DateTime => :date_time?,
FalseClass => :false?,
Integer => :int?,
NilClass => :nil?,
String => :str?,
TrueClass => :true?,
BigDecimal => :decimal?
}.freeze
REDUCED_TYPES = {
[[[:true?], [:false?]]] => %i[bool?]
}.freeze
HASH = %i[hash?].freeze
ARRAY = %i[array?].freeze
NIL = %i[nil?].freeze
# Compiler reduces type AST into a list of predicates
#
# @api private
class Compiler
# @return [PredicateRegistry]
# @api private
attr_reader :registry
# @api private
def initialize(registry)
@registry = registry
end
# @api private
def infer_predicate(type)
[TYPE_TO_PREDICATE.fetch(type) { :"#{type.name.split('::').last.downcase}?" }]
end
# @api private
def visit(node)
meth, rest = node
public_send(:"visit_#{meth}", rest)
end
# @api private
def visit_nominal(node)
type = node[0]
predicate = infer_predicate(type)
if registry.key?(predicate[0])
predicate
else
[type?: type]
end
end
# @api private
def visit_hash(_)
HASH
end
# @api private
def visit_array(_)
ARRAY
end
# @api private
def visit_lax(node)
visit(node)
end
# @api private
def visit_constructor(node)
other, * = node
visit(other)
end
# @api private
def visit_enum(node)
other, * = node
visit(other)
end
# @api private
def visit_sum(node)
left_node, right_node, = node
left = visit(left_node)
right = visit(right_node)
if left.eql?(NIL)
right
else
[[left, right]]
end
end
# @api private
def visit_constrained(node)
other, rules = node
predicates = visit(rules)
if predicates.empty?
visit(other)
else
[*visit(other), *merge_predicates(predicates)]
end
end
# @api private
def visit_any(_)
EMPTY_ARRAY
end
# @api private
def visit_and(node)
left, right = node
visit(left) + visit(right)
end
# @api private
def visit_predicate(node)
pred, args = node
if pred.equal?(:type?)
EMPTY_ARRAY
elsif registry.key?(pred)
*curried, _ = args
values = curried.map { |_, v| v }
if values.empty?
[pred]
else
[pred => values[0]]
end
else
EMPTY_ARRAY
end
end
private
# @api private
def merge_predicates(nodes)
preds, merged = nodes.each_with_object([[], {}]) do |predicate, (ps, h)|
if predicate.is_a?(::Hash)
h.update(predicate)
else
ps << predicate
end
end
merged.empty? ? preds : [*preds, merged]
end
end
# @return [Compiler]
# @api private
attr_reader :compiler
# @api private
def initialize(registry = PredicateRegistry.new)
@compiler = Compiler.new(registry)
end
# Infer predicate identifier from the provided type
#
# @param [Type] type
# @return [Symbol]
#
# @api private
def [](type)
self.class.fetch_or_store(type) do
predicates = compiler.visit(type.to_ast)
if predicates.is_a?(::Hash)
predicates
else
REDUCED_TYPES[predicates] || predicates
end
end
end
end
end
end
|
