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).

@private @sig Array

autoloads[R]

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]]

mutex[R]

@private @sig Mutex

mutex2[R]

@private @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.

@private @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.

@private @sig Set

to_unload[R]

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]]]

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 321
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 293
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 307
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 284
def for_gem(warn_on_extra_files: true)
  called_from = caller_locations(1, 1).first.path
  Registry.loader_for_gem(called_from, warn_on_extra_files: warn_on_extra_files)
end
new() click to toggle source
Calls superclass method Zeitwerk::Loader::Config::new
# File lib/zeitwerk/loader.rb, line 96
def initialize
  super

  @autoloads       = {}
  @autoloaded_dirs = []
  @to_unload       = {}
  @namespace_dirs  = Hash.new { |h, cpath| h[cpath] = [] }
  @shadowed_files  = Set.new
  @mutex           = Mutex.new
  @mutex2          = Mutex.new
  @setup           = false
  @eager_loaded    = false

  Registry.register_loader(self)
end

Public Instance Methods

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 219
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 115
def setup
  mutex.synchronize do
    break if @setup

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

    on_setup_callbacks.each(&:call)

    @setup = true
  end
end
shadowed_file?(file) click to toggle source

The return value of this predicate is only meaningful if the loader has scanned the file. This is the case in the spots where we use it.

@private @sig (String) -> Boolean

# File lib/zeitwerk/loader.rb, line 259
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 avaiable to be used together with `unregister`, which is undocumented too.

@sig () -> void

# File lib/zeitwerk/loader.rb, line 141
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, (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?
        begin
          value = cget(parent, cname)
        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(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
    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 233
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 241
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 249
def unregister
  Registry.unregister_loader(self)
  ExplicitNamespace.__unregister_loader(self)
end