class Zeitwerk::Loader

Attributes

default_logger[RW]

@return [#call, debug, nil]

mutex[RW]

@private @return [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 @return [<String>]

autoloads[R]

Maps real 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 @return [{String => (Module, Symbol)}]

eager_load_exclusions[R]

Absolute paths of files or directories not to be eager loaded.

@private @return [Set<String>]

ignored_glob_patterns[R]

Absolute paths of files, directories, of glob patterns to be totally ignored.

@private @return [Set<String>]

ignored_paths[R]

The actual collection of absolute file and directory names at the time the ignored glob patterns were expanded. Computed on setup, and recomputed on reload.

@private @return [Set<String>]

inflector[RW]

@return [#camelize]

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 @return [{String => <String>}]

logger[RW]

@return [#call, debug, nil]

mutex[R]

@private @return [Mutex]

mutex2[R]

@private @return [Mutex]

preloads[R]

Absolute paths of files or directories that have to be preloaded.

@private @return [<String>]

root_dirs[R]

Absolute paths of the root directories. Stored in a hash to preserve order, easily handle duplicates, and also be able to have a fast lookup, needed for detecting nested paths.

"/Users/fxn/blog/app/assets"   => true,
"/Users/fxn/blog/app/channels" => true,
...

This is a private collection maintained by the loader. The public interface for it is `push_dir` and `dirs`.

@private @return [{String => true}]

tag[R]

@return [String]

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 real 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 @return [{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.

@return [<String>]

# File lib/zeitwerk/loader.rb, line 456
def all_dirs
  Registry.loaders.flat_map(&:dirs).freeze
end
eager_load_all() click to toggle source

Broadcasts `eager_load` to all loaders.

@return [void]

# File lib/zeitwerk/loader.rb, line 448
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
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.

@return [Zeitwerk::Loader]

# File lib/zeitwerk/loader.rb, line 440
def for_gem
  called_from = caller_locations(1, 1).first.path
  Registry.loader_for_gem(called_from)
end
new() click to toggle source
# File lib/zeitwerk/loader.rb, line 127
def initialize
  @initialized_at = Time.now

  @tag       = SecureRandom.hex(3)
  @inflector = Inflector.new
  @logger    = self.class.default_logger

  @root_dirs             = {}
  @preloads              = []
  @ignored_glob_patterns = Set.new
  @ignored_paths         = Set.new
  @autoloads             = {}
  @autoloaded_dirs       = []
  @to_unload             = {}
  @lazy_subdirs          = {}
  @eager_load_exclusions = Set.new

  # TODO: find a better name for these mutexes.
  @mutex        = Mutex.new
  @mutex2       = Mutex.new
  @setup        = false
  @eager_loaded = false

  @reloading_enabled = false

  Registry.register_loader(self)
end

Public Instance Methods

dirs() click to toggle source

Absolute paths of the root directories. This is a read-only collection, please push here via `push_dir`.

@return [<String>]

# File lib/zeitwerk/loader.rb, line 166
def dirs
  root_dirs.keys.freeze
end
do_not_eager_load(*paths) click to toggle source

Let eager load ignore the given files or directories. The constants defined in those files are still autoloadable.

@param paths [<String, Pathname, <String, Pathname>>] @return [void]

# File lib/zeitwerk/loader.rb, line 374
def do_not_eager_load(*paths)
  mutex.synchronize { eager_load_exclusions.merge(expand_paths(paths)) }
end
eager_load() 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`.

@return [void]

# File lib/zeitwerk/loader.rb, line 337
def eager_load
  mutex.synchronize do
    break if @eager_loaded

    queue = actual_root_dirs.reject { |dir| eager_load_exclusions.member?(dir) }
    queue.map! { |dir| [Object, dir] }
    while to_eager_load = queue.shift
      namespace, dir = to_eager_load

      ls(dir) do |basename, abspath|
        next if eager_load_exclusions.member?(abspath)

        if ruby?(abspath)
          if cref = autoloads[File.realpath(abspath)]
            cref[0].const_get(cref[1], false)
          end
        elsif dir?(abspath) && !root_dirs.key?(abspath)
          cname = inflector.camelize(basename, abspath)
          queue << [namespace.const_get(cname, false), abspath]
        end
      end
    end

    autoloaded_dirs.each do |autoloaded_dir|
      Registry.unregister_autoload(autoloaded_dir)
    end
    autoloaded_dirs.clear

    @eager_loaded = true
  end
end
enable_reloading() click to toggle source

You need to call this method before setup in order to be able to reload. There is no way to undo this, either you want to reload or you don't.

@raise [Zeitwerk::Error] @return [void]

# File lib/zeitwerk/loader.rb, line 194
def enable_reloading
  mutex.synchronize do
    break if @reloading_enabled

    if @setup
      raise Error, "cannot enable reloading after setup"
    else
      @reloading_enabled = true
    end
  end
end
ignore(*glob_patterns) click to toggle source

Configure files, directories, or glob patterns to be totally ignored.

@param paths [<String, Pathname, <String, Pathname>>] @return [void]

# File lib/zeitwerk/loader.rb, line 228
def ignore(*glob_patterns)
  glob_patterns = expand_paths(glob_patterns)
  mutex.synchronize do
    ignored_glob_patterns.merge(glob_patterns)
    ignored_paths.merge(expand_glob_patterns(glob_patterns))
  end
end
log!() click to toggle source

Logs to `$stdout`, handy shortcut for debugging.

@return [void]

# File lib/zeitwerk/loader.rb, line 398
def log!
  @logger = ->(msg) { puts msg }
end
manages?(dir) click to toggle source

@private @param dir [String] @return [Boolean]

# File lib/zeitwerk/loader.rb, line 405
def manages?(dir)
  dir = dir + "/"
  ignored_paths.each do |ignored_path|
    return false if dir.start_with?(ignored_path + "/")
  end

  root_dirs.each_key do |root_dir|
    return true if root_dir.start_with?(dir) || dir.start_with?(root_dir + "/")
  end

  false
end
preload(*paths) click to toggle source

Files or directories to be preloaded instead of lazy loaded.

@param paths [<String, Pathname, <String, Pathname>>] @return [void]

# File lib/zeitwerk/loader.rb, line 215
def preload(*paths)
  mutex.synchronize do
    expand_paths(paths).each do |abspath|
      preloads << abspath
      do_preload_abspath(abspath) if @setup
    end
  end
end
push_dir(path) click to toggle source

Pushes `path` to the list of root directories.

Raises `Zeitwerk::Error` if `path` does not exist, or if another loader in the same process already manages that directory or one of its ascendants or descendants.

@param path [<String, Pathname>] @raise [Zeitwerk::Error] @return [void]

# File lib/zeitwerk/loader.rb, line 179
def push_dir(path)
  abspath = File.expand_path(path)
  if dir?(abspath)
    raise_if_conflicting_directory(abspath)
    root_dirs[abspath] = true
  else
    raise Error, "the root directory #{abspath} does not exist"
  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] @return [void]

# File lib/zeitwerk/loader.rb, line 321
def reload
  if reloading_enabled?
    unload
    recompute_ignored_paths
    setup
  else
    raise ReloadingDisabledError, "can't reload, please call loader.enable_reloading before setup"
  end
end
reloading_enabled?() click to toggle source

@return [Boolean]

# File lib/zeitwerk/loader.rb, line 207
def reloading_enabled?
  @reloading_enabled
end
setup() click to toggle source

Sets autoloads in the root namespace and preloads files, if any.

@return [void]

# File lib/zeitwerk/loader.rb, line 239
def setup
  mutex.synchronize do
    break if @setup

    actual_root_dirs.each { |root_dir| set_autoloads_in_dir(root_dir, Object) }
    do_preload

    @setup = true
  end
end
tag=(tag) click to toggle source

Sets a tag for the loader, useful for logging.

@return [void]

# File lib/zeitwerk/loader.rb, line 158
def tag=(tag)
  @tag = tag.to_s
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.

@private @return [void]

# File lib/zeitwerk/loader.rb, line 259
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 |realpath, (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)   if cdef?(parent, cname)
        unloaded_files.add(realpath) if ruby?(realpath)
      end
    end

    to_unload.each_value do |(realpath, (parent, cname))|
      unload_cref(parent, cname)   if cdef?(parent, cname)
      unloaded_files.add(realpath) if ruby?(realpath)
    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(self)

    @setup = 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.

@param cpath [String] @return [Boolean]

# File lib/zeitwerk/loader.rb, line 383
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.

@return [<String>]

# File lib/zeitwerk/loader.rb, line 391
def unloadable_cpaths
  to_unload.keys.freeze
end