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# Every file should have a "typed sigil" that tells Sorbet how strict to be
# during static type checking.
#
# Strictness levels (lax to strict):
#
# ignore: Sorbet won't even read the file. This means its contents are not
# visible during type checking. Avoid this.
#
# false: Sorbet will only report errors related to constant resolution. This
# is the default if no sigil is included.
#
# true: Sorbet will report all static type errors. This is the sweet spot of
# safety for effort.
#
# strict: Sorbet will require that all methods, constants, and instance
# variables have static types.
#
# strong: Sorbet will no longer allow anything to be T.untyped, even
# explicitly. Almost nothing satisfies this.
# typed: true
# Include the runtime type-checking library. This lets you write inline sigs
# and have them checked at runtime (instead of running Sorbet as RBI-only).
# These runtime checks happen even for files with `ignore` or `false` sigils.
require 'sorbet-runtime'
module BasicSigs
# Bring in the type definition helpers. You'll almost always need this.
extend T::Sig
# Sigs are defined with `sig` and a block. Define the return value type with
# `returns`.
#
# This method returns a value whose class is `String`. These are the most
# common types, and Sorbet calls them "class types".
sig { returns(String) }
def greet
'Hello, World!'
end
# Define parameter value types with `params`.
sig { params(n: Integer).returns(String) }
def greet_repeat(n)
(1..n).map { greet }.join("\n")
end
# Define keyword parameters the same way.
sig { params(n: Integer, sep: String).returns(String) }
def greet_repeat(n, sep: "\n")
(1..n).map { greet }.join(sep)
end
# Notice that positional/keyword and required/optional make no difference
# here. They're all defined the same way in `params`.
# For lots of parameters, it's nicer to use do..end and a multiline block
# instead of curly braces.
sig do
params(
str: String,
num: Integer,
sym: Symbol,
).returns(String)
end
def uhh(str:, num:, sym:)
'What would you even do with these?'
end
# For a method whose return value is useless, use `void`.
sig { params(name: String).void }
def say_hello(name)
puts "Hello, #{name}!"
end
# Splats! Also known as "rest parameters", "*args", "**kwargs", and others.
#
# Type the value that a _member_ of `args` or `kwargs` will have, not `args`
# or `kwargs` itself.
sig { params(args: Integer, kwargs: String).void }
def no_op(*args, **kwargs)
if kwargs[:op] == 'minus'
args.each { |i| puts(i - 1) }
else
args.each { |i| puts(i + 1) }
end
end
# Most initializers should be `void`.
sig { params(name: String).void }
def initialize(name:)
# Instance variables must have annotated types to participate in static
# type checking.
# The value in `T.let` is checked statically and at runtime.
@upname = T.let(name.upcase, String)
# Sorbet can infer this one!
@name = name
end
# Constants also need annotated types.
SORBET = T.let('A delicious frozen treat', String)
# Class variables too.
@@the_answer = T.let(42, Integer)
end
module StandardHelpers
extend T::Sig
# Sorbet provides some helpers for typing the Ruby standard library.
# Use T::Boolean to catch both `true` and `false`.
#
# For the curious, this is equivalent to
# T.type_alias { T.any(TrueClass, FalseClass) }
sig { params(str: String).returns(T::Boolean) }
def confirmed?(str)
str == 'yes'
end
# Reminder that the value `nil` is an instance of NilClass.
sig { params(val: NilClass).void }
def only_nil(val:); end
# To avoid modifying common standard library classes, Sorbet provides
# wrappers to support common generics.
#
# Here's the full list:
# * T::Array
# * T::Enumerable
# * T::Enumerator
# * T::Hash
# * T::Range
# * T::Set
sig { params(config: T::Hash[Symbol, String]).returns(T::Array[String]) }
def merge_values(config)
keyset = [:old_key, :new_key]
config.each_pair.flat_map do |key, value|
keyset.include?(key) ? value : nil
end
end
# Sometimes (usually dependency injection), a method will accept a reference
# to a class rather than an instance of the class. Use `T.class_of(Dep)` to
# accept the `Dep` class itself (or something that inherits from it).
class Dep; end
sig { params(dep: T.class_of(Dep)).returns(Dep) }
def dependency_injection(dep:)
dep.new
end
# Blocks, procs, and lambdas, oh my! All of these are typed with `T.proc`.
#
# Limitations:
# 1. All parameters are assumed to be required positional parameters.
# 2. The only runtime check is that the value is a `Proc`. The argument
# types are only checked statically.
sig do
params(
data: T::Array[String],
blk: T.proc.params(val: String).returns(Integer),
).returns(Integer)
end
def count(data, &blk)
data.sum(&blk)
end
sig { returns(Integer) }
def count_usage
count(["one", "two", "three"]) { |word| word.length + 1 }
end
# If the method takes an implicit block, Sorbet will infer `T.untyped` for
# it. Use the explicit block syntax if the types are important.
sig { params(str: String).returns(T.untyped) }
def implicit_block(str)
yield(str)
end
# If you're writing a DSL and will execute the block in a different context,
# use `bind`.
sig { params(num: Integer, blk: T.proc.bind(Integer).void).void }
def number_fun(num, &blk)
num.instance_eval(&blk)
end
sig { void }
def number_fun_usage(num)
number_fun(10) { puts digits.join }
end
# If the block doesn't take any parameters, don't include `params`.
sig { params(blk: T.proc.returns(Integer)).returns(Integer) }
def doubled_block(&blk)
2 * blk.call
end
end
module Combinators
extend T::Sig
# These methods let you define new types from existing types.
# Use `T.any` when you have a value that can be one of many types. These are
# sometimes known as "union types" or "sum types".
sig { params(num: T.any(Integer, Float)).returns(Integer) }
def hundreds(num)
num.round(-2)
end
# `T.nilable(Type)` is a convenient alias for `T.any(Type, NilClass)`.
sig { params(val: T.nilable(String)).returns(Integer) }
def strlen(val)
val.nil? ? -1 : val.length
end
# Use `T.all` when you have a value that must be satisfy multiple types.
# These are sometimes known as "intersection types". They're most useful for
# interfaces (described later), but can also be useful for helper modules.
module Reversible
extend T::Sig
sig { void }
def reverse
# Pretend this is actually implemented
end
end
module Sortable
extend T::Sig
sig { void }
def sort
# Pretend this is actually implemented
end
end
class List
include Reversible
include Sortable
end
sig { params(list: T.all(Reversible, Sortable)).void }
def rev_sort(list)
# reverse from Reversible
list.reverse
# sort from Sortable
list.sort
end
def rev_sort_usage
rev_sort(List.new)
end
end
module DataClasses
# Use `T::Struct` to create a new class with type-checked fields. It
# combines the best parts of the standard Struct and OpenStruct, and then
# adds static typing on top.
#
# Types constructed this way are sometimes known as "product types".
class Matcher < T::Struct
# Use `prop` to define a field with both a reader and writer.
prop :count, Integer
# Use `const` to only define the reader and skip the writer.
const :pattern, Regexp
# You can still set a default value with `default`.
const :message, String, default: 'Found one!'
# This is otherwise a normal class, so you can still define methods.
# You'll still need to bring `sig` in if you want to use it though.
extend T::Sig
sig { void }
def reset
self.count = 0
end
end
sig { params(text: String, matchers: T::Array[Matcher]).void }
def awk(text, matchers)
matchers.each(&:reset)
text.lines.each do |line|
matchers.each do |matcher|
if matcher.pattern =~ line
puts matcher.message
matcher.count += 1
end
end
end
end
# Gotchas and limitations
# 1. `const` fields are not truly immutable. They don't have a writer
# method, but may be changed in other ways.
class ChangeMe < T::Struct
const :list, T::Array[Integer]
end
def whoops!(change_me)
change_me = ChangeMe.new(list: [1, 2, 3, 4])
change_me.list.reverse!
change_me.list == [4, 3, 2, 1]
end
# 2. `T::Struct` inherits its equality method from `BasicObject`, which uses
# identity equality (also known as "reference equality").
class Position < T::Struct
const :x, Integer
const :y, Integer
end
def never_equal!
p1 = Position.new(x: 1, y: 2)
p2 = Position.new(x: 1, y: 2)
p1 != p2
end
# Define your own `#==` method to check the fields, if that's what you want.
class Position < T::Struct
# Note: reopened class
def ==(other)
self.class == other.class && self.x == other.x && self.y == other.y
end
end
# Use `T::Enum` to define a fixed set of values that are easy to reference.
# This is especially useful when you don't care what the values _are_ as much
# as you care that the set of possibilities is closed and static.
class Crayon < T::Enum
# Start initialization with `enum`.
enums do
# Define each member with `new`. Each of these is an instance of the
# `Crayon` class.
Red = new
Orange = new
Yellow = new
Green = new
Blue = new
Violet = new
Brown = new
Black = new
# The default value of the enum is its name in all-lowercase. To change
# that, pass a value to `new`.
Gray90 = new('light-gray')
end
# Define any aliases outside the initialization block.
Purple = Violet
# Also, `sig` is already included here.
sig { returns(String) }
def to_hex
case self
when Red then '#ff0000'
when Green then '#00ff00'
# ...
else '#ffffff'
end
end
end
sig { params(crayon: Crayon, path: T::Array[Point]).void }
def draw(crayon:, path:)
path.each do |point|
puts "(#{point.x}, #{point.y}) = " + crayon.to_hex
end
end
end
module FlowSensitivity
# works with T.any and T::Enum
# TODO: T.absurd
# TODO: T.noreturn
end
module Metaprogramming
# TODO: T.type_alias
# TODO: T.self_type
# TODO: T.attached_class
end
module InheritanceChecks
# TODO: abstract!
# TODO: interface!
# TODO: abstract. / override.
# TODO: mixes_in_class_methods
# TODO: final!
# TODO: sealed!
end
module Debugging
# TODO: T.reveal_type
end
module EscapeHatches
# TODO: T.untyped
# TODO: T.cast
# TODO: T.unsafe
# TODO: T.must
# TODO: T.assert_type!
end
# The following types are not officially documented but are still useful.
module ValueSet
# TODO: T.enum
end
module Generics
# TODO: type_parameters / T.type_parameter
# TODO: T::Generic
# TODO: type_member
end
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