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loader.rb
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loader.rb
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# frozen_string_literal: true
require "set"
module Zeitwerk
class Loader
require_relative "loader/helpers"
require_relative "loader/callbacks"
require_relative "loader/config"
include RealModName
include Callbacks
include Helpers
include Config
# Maps absolute paths for which an autoload has been set ---and not
# executed--- to their corresponding parent class or module and constant
# name.
#
# "/Users/fxn/blog/app/models/user.rb" => [Object, :User],
# "/Users/fxn/blog/app/models/hotel/pricing.rb" => [Hotel, :Pricing]
# ...
#
# @private
# @sig Hash[String, [Module, Symbol]]
attr_reader :autoloads
# We keep track of autoloaded directories to remove them from the registry
# at the end of eager loading.
#
# Files are removed as they are autoloaded, but directories need to wait due
# to concurrency (see why in Zeitwerk::Loader::Callbacks#on_dir_autoloaded).
#
# @private
# @sig Array[String]
attr_reader :autoloaded_dirs
# Stores metadata needed for unloading. Its entries look like this:
#
# "Admin::Role" => [".../admin/role.rb", [Admin, :Role]]
#
# The cpath as key helps implementing unloadable_cpath? The file name is
# stored in order to be able to delete it from $LOADED_FEATURES, and the
# pair [Module, Symbol] is used to remove_const the constant from the class
# or module object.
#
# If reloading is enabled, this hash is filled as constants are autoloaded
# or eager loaded. Otherwise, the collection remains empty.
#
# @private
# @sig Hash[String, [String, [Module, Symbol]]]
attr_reader :to_unload
# Maps constant paths of namespaces to arrays of corresponding directories.
#
# For example, given this mapping:
#
# "Admin" => [
# "/Users/fxn/blog/app/controllers/admin",
# "/Users/fxn/blog/app/models/admin",
# ...
# ]
#
# when `Admin` gets defined we know that it plays the role of a namespace and
# that its children are spread over those directories. We'll visit them to set
# up the corresponding autoloads.
#
# @private
# @sig Hash[String, Array[String]]
attr_reader :lazy_subdirs
# @private
# @sig Mutex
attr_reader :mutex
# @private
# @sig Mutex
attr_reader :mutex2
def initialize
super
@autoloads = {}
@autoloaded_dirs = []
@to_unload = {}
@lazy_subdirs = Hash.new { |h, cpath| h[cpath] = [] }
@mutex = Mutex.new
@mutex2 = Mutex.new
@setup = false
@eager_loaded = false
Registry.register_loader(self)
end
# Sets autoloads in the root namespace.
#
# @sig () -> void
def setup
mutex.synchronize do
break if @setup
actual_root_dirs.each do |root_dir, namespace|
set_autoloads_in_dir(root_dir, namespace)
end
on_setup_callbacks.each(&:call)
@setup = true
end
end
# Removes loaded constants and configured autoloads.
#
# The objects the constants stored are no longer reachable through them. In
# addition, since said objects are normally not referenced from anywhere
# else, they are eligible for garbage collection, which would effectively
# unload them.
#
# This method is public but undocumented. Main interface is `reload`, which
# means `unload` + `setup`. This one is avaiable to be used together with
# `unregister`, which is undocumented too.
#
# @sig () -> void
def unload
mutex.synchronize do
# We are going to keep track of the files that were required by our
# autoloads to later remove them from $LOADED_FEATURES, thus making them
# loadable by Kernel#require again.
#
# Directories are not stored in $LOADED_FEATURES, keeping track of files
# is enough.
unloaded_files = Set.new
autoloads.each do |abspath, (parent, cname)|
if parent.autoload?(cname)
unload_autoload(parent, cname)
else
# Could happen if loaded with require_relative. That is unsupported,
# and the constant path would escape unloadable_cpath? This is just
# defensive code to clean things up as much as we are able to.
unload_cref(parent, cname)
unloaded_files.add(abspath) if ruby?(abspath)
end
end
to_unload.each do |cpath, (abspath, (parent, cname))|
unless on_unload_callbacks.empty?
value = parent.const_get(cname)
run_on_unload_callbacks(cpath, value, abspath)
end
unload_cref(parent, cname)
unloaded_files.add(abspath) if ruby?(abspath)
end
unless unloaded_files.empty?
# Bootsnap decorates Kernel#require to speed it up using a cache and
# this optimization does not check if $LOADED_FEATURES has the file.
#
# To make it aware of changes, the gem defines singleton methods in
# $LOADED_FEATURES:
#
# https://github.com/Shopify/bootsnap/blob/master/lib/bootsnap/load_path_cache/core_ext/loaded_features.rb
#
# Rails applications may depend on bootsnap, so for unloading to work
# in that setting it is preferable that we restrict our API choice to
# one of those methods.
$LOADED_FEATURES.reject! { |file| unloaded_files.member?(file) }
end
autoloads.clear
autoloaded_dirs.clear
to_unload.clear
lazy_subdirs.clear
Registry.on_unload(self)
ExplicitNamespace.unregister_loader(self)
@setup = false
@eager_loaded = false
end
end
# Unloads all loaded code, and calls setup again so that the loader is able
# to pick any changes in the file system.
#
# This method is not thread-safe, please see how this can be achieved by
# client code in the README of the project.
#
# @raise [Zeitwerk::Error]
# @sig () -> void
def reload
if reloading_enabled?
unload
recompute_ignored_paths
recompute_collapse_dirs
setup
else
raise ReloadingDisabledError, "can't reload, please call loader.enable_reloading before setup"
end
end
# Eager loads all files in the root directories, recursively. Files do not
# need to be in `$LOAD_PATH`, absolute file names are used. Ignored files
# are not eager loaded. You can opt-out specifically in specific files and
# directories with `do_not_eager_load`, and that can be overridden passing
# `force: true`.
#
# @sig (true | false) -> void
def eager_load(force: false)
mutex.synchronize do
break if @eager_loaded
log("eager load start") if logger
honour_exclusions = !force
queue = []
actual_root_dirs.each do |root_dir, namespace|
queue << [namespace, root_dir] unless honour_exclusions && excluded_from_eager_load?(root_dir)
end
while to_eager_load = queue.shift
namespace, dir = to_eager_load
ls(dir) do |basename, abspath|
next if honour_exclusions && excluded_from_eager_load?(abspath)
if ruby?(abspath)
if cref = autoloads[abspath]
cget(*cref)
end
elsif dir?(abspath) && !root_dirs.key?(abspath)
if collapse?(abspath)
queue << [namespace, abspath]
else
cname = inflector.camelize(basename, abspath)
queue << [cget(namespace, cname), abspath]
end
end
end
end
autoloaded_dirs.each do |autoloaded_dir|
Registry.unregister_autoload(autoloaded_dir)
end
autoloaded_dirs.clear
@eager_loaded = true
log("eager load end") if logger
end
end
# Says if the given constant path would be unloaded on reload. This
# predicate returns `false` if reloading is disabled.
#
# @sig (String) -> bool
def unloadable_cpath?(cpath)
to_unload.key?(cpath)
end
# Returns an array with the constant paths that would be unloaded on reload.
# This predicate returns an empty array if reloading is disabled.
#
# @sig () -> Array[String]
def unloadable_cpaths
to_unload.keys.freeze
end
# This is a dangerous method.
#
# @experimental
# @sig () -> void
def unregister
Registry.unregister_loader(self)
ExplicitNamespace.unregister_loader(self)
end
# --- Class methods ---------------------------------------------------------------------------
class << self
# @sig #call | #debug | nil
attr_accessor :default_logger
# @private
# @sig Mutex
attr_accessor :mutex
# This is a shortcut for
#
# require "zeitwerk"
# loader = Zeitwerk::Loader.new
# loader.tag = File.basename(__FILE__, ".rb")
# loader.inflector = Zeitwerk::GemInflector.new(__FILE__)
# loader.push_dir(__dir__)
#
# except that this method returns the same object in subsequent calls from
# the same file, in the unlikely case the gem wants to be able to reload.
#
# @sig () -> Zeitwerk::Loader
def for_gem
called_from = caller_locations(1, 1).first.path
Registry.loader_for_gem(called_from)
end
# Broadcasts `eager_load` to all loaders.
#
# @sig () -> void
def eager_load_all
Registry.loaders.each(&:eager_load)
end
# Returns an array with the absolute paths of the root directories of all
# registered loaders. This is a read-only collection.
#
# @sig () -> Array[String]
def all_dirs
Registry.loaders.flat_map(&:dirs).freeze
end
end
self.mutex = Mutex.new
private # -------------------------------------------------------------------------------------
# @sig (String, Module) -> void
def set_autoloads_in_dir(dir, parent)
ls(dir) do |basename, abspath|
begin
if ruby?(basename)
basename.delete_suffix!(".rb")
cname = inflector.camelize(basename, abspath).to_sym
autoload_file(parent, cname, abspath)
elsif dir?(abspath)
# In a Rails application, `app/models/concerns` is a subdirectory of
# `app/models`, but both of them are root directories.
#
# To resolve the ambiguity file name -> constant path this introduces,
# the `app/models/concerns` directory is totally ignored as a namespace,
# it counts only as root. The guard checks that.
unless root_dir?(abspath)
cname = inflector.camelize(basename, abspath).to_sym
if collapse?(abspath)
set_autoloads_in_dir(abspath, parent)
else
autoload_subdir(parent, cname, abspath)
end
end
end
rescue ::NameError => error
path_type = ruby?(abspath) ? "file" : "directory"
raise NameError.new(<<~MESSAGE, error.name)
#{error.message} inferred by #{inflector.class} from #{path_type}
#{abspath}
Possible ways to address this:
* Tell Zeitwerk to ignore this particular #{path_type}.
* Tell Zeitwerk to ignore one of its parent directories.
* Rename the #{path_type} to comply with the naming conventions.
* Modify the inflector to handle this case.
MESSAGE
end
end
end
# @sig (Module, Symbol, String) -> void
def autoload_subdir(parent, cname, subdir)
if autoload_path = autoload_path_set_by_me_for?(parent, cname)
cpath = cpath(parent, cname)
register_explicit_namespace(cpath) if ruby?(autoload_path)
# We do not need to issue another autoload, the existing one is enough
# no matter if it is for a file or a directory. Just remember the
# subdirectory has to be visited if the namespace is used.
lazy_subdirs[cpath] << subdir
elsif !cdef?(parent, cname)
# First time we find this namespace, set an autoload for it.
lazy_subdirs[cpath(parent, cname)] << subdir
set_autoload(parent, cname, subdir)
else
# For whatever reason the constant that corresponds to this namespace has
# already been defined, we have to recurse.
log("the namespace #{cpath(parent, cname)} already exists, descending into #{subdir}") if logger
set_autoloads_in_dir(subdir, cget(parent, cname))
end
end
# @sig (Module, Symbol, String) -> void
def autoload_file(parent, cname, file)
if autoload_path = strict_autoload_path(parent, cname) || Registry.inception?(cpath(parent, cname))
# First autoload for a Ruby file wins, just ignore subsequent ones.
if ruby?(autoload_path)
log("file #{file} is ignored because #{autoload_path} has precedence") if logger
else
promote_namespace_from_implicit_to_explicit(
dir: autoload_path,
file: file,
parent: parent,
cname: cname
)
end
elsif cdef?(parent, cname)
log("file #{file} is ignored because #{cpath(parent, cname)} is already defined") if logger
else
set_autoload(parent, cname, file)
end
end
# `dir` is the directory that would have autovivified a namespace. `file` is
# the file where we've found the namespace is explicitly defined.
#
# @sig (dir: String, file: String, parent: Module, cname: Symbol) -> void
def promote_namespace_from_implicit_to_explicit(dir:, file:, parent:, cname:)
autoloads.delete(dir)
Registry.unregister_autoload(dir)
log("earlier autoload for #{cpath(parent, cname)} discarded, it is actually an explicit namespace defined in #{file}") if logger
set_autoload(parent, cname, file)
register_explicit_namespace(cpath(parent, cname))
end
# @sig (Module, Symbol, String) -> void
def set_autoload(parent, cname, abspath)
parent.autoload(cname, abspath)
if logger
if ruby?(abspath)
log("autoload set for #{cpath(parent, cname)}, to be loaded from #{abspath}")
else
log("autoload set for #{cpath(parent, cname)}, to be autovivified from #{abspath}")
end
end
autoloads[abspath] = [parent, cname]
Registry.register_autoload(self, abspath)
# See why in the documentation of Zeitwerk::Registry.inceptions.
unless parent.autoload?(cname)
Registry.register_inception(cpath(parent, cname), abspath, self)
end
end
# @sig (Module, Symbol) -> String?
def autoload_path_set_by_me_for?(parent, cname)
if autoload_path = strict_autoload_path(parent, cname)
autoload_path if autoloads.key?(autoload_path)
else
Registry.inception?(cpath(parent, cname))
end
end
# @sig (String) -> void
def register_explicit_namespace(cpath)
ExplicitNamespace.register(cpath, self)
end
# @sig (String) -> void
def raise_if_conflicting_directory(dir)
self.class.mutex.synchronize do
Registry.loaders.each do |loader|
next if loader == self
next if loader.ignores?(dir)
dir = dir + "/"
loader.root_dirs.each do |root_dir, _namespace|
next if ignores?(root_dir)
root_dir = root_dir + "/"
if dir.start_with?(root_dir) || root_dir.start_with?(dir)
require "pp" # Needed for pretty_inspect, even in Ruby 2.5.
raise Error,
"loader\n\n#{pretty_inspect}\n\nwants to manage directory #{dir.chop}," \
" which is already managed by\n\n#{loader.pretty_inspect}\n"
EOS
end
end
end
end
end
# @sig (String, Object, String) -> void
def run_on_unload_callbacks(cpath, value, abspath)
# Order matters. If present, run the most specific one.
on_unload_callbacks[cpath]&.each { |c| c.call(value, abspath) }
on_unload_callbacks[:ANY]&.each { |c| c.call(cpath, value, abspath) }
end
# @sig (Module, Symbol) -> void
def unload_autoload(parent, cname)
parent.__send__(:remove_const, cname)
log("autoload for #{cpath(parent, cname)} removed") if logger
end
# @sig (Module, Symbol) -> void
def unload_cref(parent, cname)
# Let's optimistically remove_const. The way we use it, this is going to
# succeed always if all is good.
parent.__send__(:remove_const, cname)
rescue ::NameError
# There are a few edge scenarios in which this may happen. If the constant
# is gone, that is OK, anyway.
else
log("#{cpath(parent, cname)} unloaded") if logger
end
end
end