class Zeitwerk::Loader

Attributes

default_logger[RW]

@sig call | debug | nil

mutex[RW]

@private @sig Mutex

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]]

lazy_subdirs[R]

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]

mutex[R]

@private @sig Mutex

mutex2[R]

@private @sig Mutex

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 324
def all_dirs
  Registry.loaders.flat_map(&:dirs).freeze
end
eager_load_all() click to toggle source

Broadcasts `eager_load` to all loaders.

@sig () -> void

# File lib/zeitwerk/loader.rb, line 316
def eager_load_all
  Registry.loaders.each(&:eager_load)
end
for_gem() 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.

@sig () -> Zeitwerk::Loader

# File lib/zeitwerk/loader.rb, line 308
def for_gem
  called_from = caller_locations(1, 1).first.path
  Registry.loader_for_gem(called_from)
end
new() click to toggle source
Calls superclass method Zeitwerk::Loader::Config::new
# File lib/zeitwerk/loader.rb, line 80
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

Public Instance Methods

eager_load(force: false) click to toggle source

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

# File lib/zeitwerk/loader.rb, line 216
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
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 198
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
setup() click to toggle source

Sets autoloads in the root namespace.

@sig () -> void

# File lib/zeitwerk/loader.rb, line 98
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
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 124
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))|
      # We have to check cdef? in this condition. Reason is, constants whose
      # file does not define them have to be kept in to_unload as explained
      # in the implementation of on_file_autoloaded.
      #
      # If the constant is not defined, on_unload should not be triggered
      # for it.
      if !on_unload_callbacks.empty? && cdef?(parent, cname)
        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
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 265
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 273
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 281
def unregister
  Registry.unregister_loader(self)
  ExplicitNamespace.unregister_loader(self)
end