class Zeitwerk::Loader

Constants

MUTEX

Attributes

default_logger[RW]

@sig call | debug | nil

autoloaded_dirs[R]

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).

@sig Array

autoloads[R]

Maps absolute paths for which an autoload has been set —and not executed— to their corresponding Zeitwerk::Cref object.

"/Users/fxn/blog/app/models/user.rb"          => #<Zeitwerk::Cref:... @mod=Object, @cname=:User, ...>,
"/Users/fxn/blog/app/models/hotel/pricing.rb" => #<Zeitwerk::Cref:... @mod=Hotel, @cname=:Pricing, ...>,
...

@sig Hash[String, Zeitwerk::Cref]

dirs_autoload_monitor[R]

@sig Monitor

mutex[R]

@sig Mutex

namespace_dirs[R]

Maps namespace constant paths to their respective 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.

@sig Hash[String, Array]

shadowed_files[R]

A shadowed file is a file managed by this loader that is ignored when setting autoloads because its matching constant is already taken.

This private set is populated as we descend. For example, if the loader has only scanned the top-level, `shadowed_files` does not have shadowed files that may exist deep in the project tree yet.

@sig Set

to_unload[R]

Stores metadata needed for unloading. Its entries look like this:

"Admin::Role" => [
  ".../admin/role.rb",
  #<Zeitwerk::Cref:... @mod=Admin, @cname=: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 cref is used to remove the constant from the parent class or module.

If reloading is enabled, this hash is filled as constants are autoloaded or eager loaded. Otherwise, the collection remains empty.

@sig Hash[String, [String, Zeitwerk::Cref]]

Public Class Methods

all_dirs() click to toggle source

Returns an array with the absolute paths of the root directories of all registered loaders. This is a read-only collection.

@sig () -> Array

# File lib/zeitwerk/loader.rb, line 438
def all_dirs
  Registry.loaders.flat_map(&:dirs).freeze
end
eager_load_all() click to toggle source

Broadcasts `eager_load` to all loaders. Those that have not been setup are skipped.

@sig () -> void

# File lib/zeitwerk/loader.rb, line 410
def eager_load_all
  Registry.loaders.each do |loader|
    begin
      loader.eager_load
    rescue SetupRequired
      # This is fine, we eager load what can be eager loaded.
    end
  end
end
eager_load_namespace(mod) click to toggle source

Broadcasts `eager_load_namespace` to all loaders. Those that have not been setup are skipped.

@sig (Module) -> void

# File lib/zeitwerk/loader.rb, line 424
def eager_load_namespace(mod)
  Registry.loaders.each do |loader|
    begin
      loader.eager_load_namespace(mod)
    rescue SetupRequired
      # This is fine, we eager load what can be eager loaded.
    end
  end
end
for_gem(warn_on_extra_files: true) click to toggle source

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.

This method returns a subclass of Zeitwerk::Loader, but the exact type is private, client code can only rely on the interface.

@sig (bool) -> Zeitwerk::GemLoader

# File lib/zeitwerk/loader.rb, line 372
def for_gem(warn_on_extra_files: true)
  called_from = caller_locations(1, 1).first.path
  Registry.loader_for_gem(called_from, namespace: Object, warn_on_extra_files: warn_on_extra_files)
end
for_gem_extension(namespace) click to toggle source

This is a shortcut for

require "zeitwerk"

loader = Zeitwerk::Loader.new
loader.tag = namespace.name + "-" + File.basename(__FILE__, ".rb")
loader.inflector = Zeitwerk::GemInflector.new(__FILE__)
loader.push_dir(__dir__, namespace: namespace)

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.

This method returns a subclass of Zeitwerk::Loader, but the exact type is private, client code can only rely on the interface.

@sig (bool) -> Zeitwerk::GemLoader

# File lib/zeitwerk/loader.rb, line 393
def for_gem_extension(namespace)
  unless namespace.is_a?(Module) # Note that Class < Module.
    raise Zeitwerk::Error, "#{namespace.inspect} is not a class or module object, should be"
  end

  unless real_mod_name(namespace)
    raise Zeitwerk::Error, "extending anonymous namespaces is unsupported"
  end

  called_from = caller_locations(1, 1).first.path
  Registry.loader_for_gem(called_from, namespace: namespace, warn_on_extra_files: false)
end
new() click to toggle source
Calls superclass method Zeitwerk::Loader::Config::new
# File lib/zeitwerk/loader.rb, line 100
def initialize
  super

  @autoloads       = {}
  @autoloaded_dirs = []
  @to_unload       = {}
  @namespace_dirs  = Hash.new { |h, cpath| h[cpath] = [] }
  @shadowed_files  = Set.new
  @setup           = false
  @eager_loaded    = false

  @mutex = Mutex.new
  @dirs_autoload_monitor = Monitor.new

  Registry.register_loader(self)
end

Public Instance Methods

all_expected_cpaths() click to toggle source

Returns a hash that maps the absolute paths of the managed files and directories to their respective expected constant paths.

@sig () -> Hash[String, String]

# File lib/zeitwerk/loader.rb, line 238
def all_expected_cpaths
  result = {}

  actual_roots.each do |root_dir, root_namespace|
    queue = [[root_dir, real_mod_name(root_namespace)]]

    while (dir, cpath = queue.shift)
      result[dir] = cpath

      prefix = cpath == "Object" ? "" : cpath + "::"

      ls(dir) do |basename, abspath, ftype|
        if ftype == :file
          basename.delete_suffix!(".rb")
          result[abspath] = prefix + inflector.camelize(basename, abspath)
        else
          if collapse?(abspath)
            queue << [abspath, cpath]
          else
            queue << [abspath, prefix + inflector.camelize(basename, abspath)]
          end
        end
      end
    end
  end

  result
end
cpath_expected_at(path) click to toggle source

@sig (String | Pathname) -> String?

# File lib/zeitwerk/loader.rb, line 268
def cpath_expected_at(path)
  abspath = File.expand_path(path)

  raise Zeitwerk::Error.new("#{abspath} does not exist") unless File.exist?(abspath)

  return unless dir?(abspath) || ruby?(abspath)
  return if ignored_path?(abspath)

  paths = []

  if ruby?(abspath)
    basename = File.basename(abspath, ".rb")
    return if hidden?(basename)

    paths << [basename, abspath]
    walk_up_from = File.dirname(abspath)
  else
    walk_up_from = abspath
  end

  root_namespace = nil

  walk_up(walk_up_from) do |dir|
    break if root_namespace = roots[dir]
    return if ignored_path?(dir)

    basename = File.basename(dir)
    return if hidden?(basename)

    paths << [basename, abspath] unless collapse?(dir)
  end

  return unless root_namespace

  if paths.empty?
    real_mod_name(root_namespace)
  else
    cnames = paths.reverse_each.map { |b, a| cname_for(b, a) }

    if root_namespace == Object
      cnames.join("::")
    else
      "#{real_mod_name(root_namespace)}::#{cnames.join("::")}"
    end
  end
end
reload() click to toggle source

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

# File lib/zeitwerk/loader.rb, line 224
def reload
  raise ReloadingDisabledError unless reloading_enabled?
  raise SetupRequired unless @setup

  unload
  recompute_ignored_paths
  recompute_collapse_dirs
  setup
end
setup() click to toggle source

Sets autoloads in the root namespaces.

@sig () -> void

# File lib/zeitwerk/loader.rb, line 120
def setup
  mutex.synchronize do
    break if @setup

    actual_roots.each do |root_dir, root_namespace|
      define_autoloads_for_dir(root_dir, root_namespace)
    end

    on_setup_callbacks.each(&:call)

    @setup = true
  end
end
shadowed_file?(file) click to toggle source
# File lib/zeitwerk/loader.rb, line 344
         def shadowed_file?(file)
  shadowed_files.member?(file)
end
unload() click to toggle source

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 available to be used together with `unregister`, which is undocumented too.

@sig () -> void

# File lib/zeitwerk/loader.rb, line 146
def unload
  mutex.synchronize do
    raise SetupRequired unless @setup

    # 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, cref|
      if cref.autoload?
        unload_autoload(cref)
      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(cref)
        unloaded_files.add(abspath) if ruby?(abspath)
      end
    end

    to_unload.each do |cpath, (abspath, cref)|
      unless on_unload_callbacks.empty?
        begin
          value = cref.get
        rescue ::NameError
          # Perhaps the user deleted the constant by hand, or perhaps an
          # autoload failed to define the expected constant but the user
          # rescued the exception.
        else
          run_on_unload_callbacks(cpath, value, abspath)
        end
      end

      unload_cref(cref)
      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
    namespace_dirs.clear
    shadowed_files.clear

    Registry.on_unload(self)
    ExplicitNamespace.__unregister_loader(self)

    @setup        = false
    @eager_loaded = false
  end
end
unloadable_cpath?(cpath) click to toggle source

Says if the given constant path would be unloaded on reload. This predicate returns `false` if reloading is disabled.

@sig (String) -> bool

# File lib/zeitwerk/loader.rb, line 319
def unloadable_cpath?(cpath)
  to_unload.key?(cpath)
end
unloadable_cpaths() click to toggle source

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

# File lib/zeitwerk/loader.rb, line 327
def unloadable_cpaths
  to_unload.keys.freeze
end
unregister() click to toggle source

This is a dangerous method.

@experimental @sig () -> void

# File lib/zeitwerk/loader.rb, line 335
def unregister
  Registry.unregister_loader(self)
  ExplicitNamespace.__unregister_loader(self)
end

Private Instance Methods

autoload_file(cref, file) click to toggle source

@sig (Module, Symbol, String) -> void

# File lib/zeitwerk/loader.rb, line 491
        def autoload_file(cref, file)
  if autoload_path = cref.autoload? || Registry.inception?(cref.path)
    # First autoload for a Ruby file wins, just ignore subsequent ones.
    if ruby?(autoload_path)
      shadowed_files << file
      log("file #{file} is ignored because #{autoload_path} has precedence") if logger
    else
      promote_namespace_from_implicit_to_explicit(dir: autoload_path, file: file, cref: cref)
    end
  elsif cref.defined?
    shadowed_files << file
    log("file #{file} is ignored because #{cref.path} is already defined") if logger
  else
    define_autoload(cref, file)
  end
end
autoload_path_set_by_me_for?(cref) click to toggle source

@sig (Module, Symbol) -> String?

# File lib/zeitwerk/loader.rb, line 544
        def autoload_path_set_by_me_for?(cref)
  if autoload_path = cref.autoload?
    autoload_path if autoloads.key?(autoload_path)
  else
    Registry.inception?(cref.path, self)
  end
end
autoload_subdir(cref, subdir) click to toggle source

@sig (Module, Symbol, String) -> void

# File lib/zeitwerk/loader.rb, line 462
        def autoload_subdir(cref, subdir)
  if autoload_path = autoload_path_set_by_me_for?(cref)
    if ruby?(autoload_path)
      # Scanning visited a Ruby file first, and now a directory for the same
      # constant has been found. This means we are dealing with an explicit
      # namespace whose definition was seen first.
      #
      # Registering is idempotent, and we have to keep the autoload pointing
      # to the file. This may run again if more directories are found later
      # on, no big deal.
      register_explicit_namespace(cref.path)
    end
    # If the existing autoload points to a file, it has to be preserved, if
    # not, it is fine as it is. In either case, we do not need to override.
    # Just remember the subdirectory conforms this namespace.
    namespace_dirs[cref.path] << subdir
  elsif !cref.defined?
    # First time we find this namespace, set an autoload for it.
    namespace_dirs[cref.path] << subdir
    define_autoload(cref, subdir)
  else
    # For whatever reason the constant that corresponds to this namespace has
    # already been defined, we have to recurse.
    log("the namespace #{cref.path} already exists, descending into #{subdir}") if logger
    define_autoloads_for_dir(subdir, cref.get)
  end
end
define_autoload(cref, abspath) click to toggle source

@sig (Module, Symbol, String) -> void

# File lib/zeitwerk/loader.rb, line 523
        def define_autoload(cref, abspath)
  cref.autoload(abspath)

  if logger
    if ruby?(abspath)
      log("autoload set for #{cref.path}, to be loaded from #{abspath}")
    else
      log("autoload set for #{cref.path}, to be autovivified from #{abspath}")
    end
  end

  autoloads[abspath] = cref
  Registry.register_autoload(self, abspath)

  # See why in the documentation of Zeitwerk::Registry.inceptions.
  unless cref.autoload?
    Registry.register_inception(cref.path, abspath, self)
  end
end
define_autoloads_for_dir(dir, parent) click to toggle source

@sig (String, Module) -> void

# File lib/zeitwerk/loader.rb, line 444
        def define_autoloads_for_dir(dir, parent)
  ls(dir) do |basename, abspath, ftype|
    if ftype == :file
      basename.delete_suffix!(".rb")
      cref = Cref.new(parent, cname_for(basename, abspath))
      autoload_file(cref, abspath)
    else
      if collapse?(abspath)
        define_autoloads_for_dir(abspath, parent)
      else
        cref = Cref.new(parent, cname_for(basename, abspath))
        autoload_subdir(cref, abspath)
      end
    end
  end
end
promote_namespace_from_implicit_to_explicit(dir:, file:, cref:) click to toggle source

`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, cref: Zeitwerk::Cref) -> void

# File lib/zeitwerk/loader.rb, line 512
        def promote_namespace_from_implicit_to_explicit(dir:, file:, cref:)
  autoloads.delete(dir)
  Registry.unregister_autoload(dir)

  log("earlier autoload for #{cref.path} discarded, it is actually an explicit namespace defined in #{file}") if logger

  define_autoload(cref, file)
  register_explicit_namespace(cref.path)
end
raise_if_conflicting_directory(dir) click to toggle source

@sig (String) -> void

# File lib/zeitwerk/loader.rb, line 558
        def raise_if_conflicting_directory(dir)
  MUTEX.synchronize do
    dir_slash = dir + "/"

    Registry.loaders.each do |loader|
      next if loader == self
      next if loader.__ignores?(dir)

      loader.__roots.each_key do |root_dir|
        next if ignores?(root_dir)

        root_dir_slash = root_dir + "/"
        if dir_slash.start_with?(root_dir_slash) || root_dir_slash.start_with?(dir_slash)
          require "pp" # Needed for pretty_inspect, even in Ruby 2.5.
          raise Error,
            "loader\n\n#{pretty_inspect}\n\nwants to manage directory #{dir}," \
            " which is already managed by\n\n#{loader.pretty_inspect}\n"
        end
      end
    end
  end
end
register_explicit_namespace(cpath) click to toggle source

@sig (String) -> void

# File lib/zeitwerk/loader.rb, line 553
        def register_explicit_namespace(cpath)
  ExplicitNamespace.__register(cpath, self)
end
run_on_unload_callbacks(cpath, value, abspath) click to toggle source

@sig (String, Object, String) -> void

# File lib/zeitwerk/loader.rb, line 582
        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
unload_autoload(cref) click to toggle source

@sig (Module, Symbol) -> void

# File lib/zeitwerk/loader.rb, line 589
        def unload_autoload(cref)
  cref.remove
  log("autoload for #{cref.path} removed") if logger
end
unload_cref(cref) click to toggle source

@sig (Module, Symbol) -> void

# File lib/zeitwerk/loader.rb, line 595
        def unload_cref(cref)
  # Let's optimistically remove_const. The way we use it, this is going to
  # succeed always if all is good.
  cref.remove
rescue ::NameError
  # There are a few edge scenarios in which this may happen. If the constant
  # is gone, that is OK, anyway.
else
  log("#{cref.path} unloaded") if logger
end