Class: Zeitwerk::Loader

Inherits:
Object
  • Object
show all
Extended by:
Internal, RealModName
Includes:
Callbacks, Config, EagerLoad, Helpers, RealModName
Defined in:
lib/zeitwerk/loader.rb

Direct Known Subclasses

GemLoader

Defined Under Namespace

Modules: Callbacks, Config, EagerLoad, Helpers

Class Attribute Summary collapse

Instance Attribute Summary collapse

Attributes included from Config

#inflector, #logger, #roots

Class Method Summary collapse

Instance Method Summary collapse

Methods included from RealModName

real_mod_name

Methods included from Internal

internal

Methods included from EagerLoad

#eager_load, #eager_load_dir, #eager_load_namespace, #load_file

Methods included from Config

#collapse, #dirs, #do_not_eager_load, #enable_reloading, #ignore, #log!, #on_load, #on_setup, #on_unload, #push_dir, #reloading_enabled?, #tag, #tag=

Methods included from Callbacks

#on_dir_autoloaded, #on_file_autoloaded, #on_namespace_loaded

Constructor Details

#initialize ⇒ Loader

Returns a new instance of Loader.



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# File 'lib/zeitwerk/loader.rb', line 98

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

Class Attribute Details

.default_logger ⇒ Object

Returns the value of attribute default_logger.



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# File 'lib/zeitwerk/loader.rb', line 333

def default_logger
  @default_logger
end

Instance Attribute Details

#autoloaded_dirs ⇒ Object (readonly)

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).



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# File 'lib/zeitwerk/loader.rb', line 42

def autoloaded_dirs
  @autoloaded_dirs
end

#autoloads ⇒ Object (readonly)

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]
...



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# File 'lib/zeitwerk/loader.rb', line 32

def autoloads
  @autoloads
end

#namespace_dirs ⇒ Object (readonly)

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.



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# File 'lib/zeitwerk/loader.rb', line 76

def namespace_dirs
  @namespace_dirs
end

#shadowed_files ⇒ Object (readonly)

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.



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# File 'lib/zeitwerk/loader.rb', line 87

def shadowed_files
  @shadowed_files
end

#to_unload ⇒ Object (readonly)

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.



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# File 'lib/zeitwerk/loader.rb', line 58

def to_unload
  @to_unload
end

Class Method Details

.all_dirs ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 417

def all_dirs
  Registry.loaders.flat_map(&:dirs).freeze
end

.eager_load_all ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 389

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) ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 403

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) ⇒ Object

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.



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# File 'lib/zeitwerk/loader.rb', line 351

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) ⇒ Object

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.



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# File 'lib/zeitwerk/loader.rb', line 372

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

Instance Method Details

#cpath_expected_at(path) ⇒ Object

Raises:



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# File 'lib/zeitwerk/loader.rb', line 232

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)

  cnames = []
  abspaths = []

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

    cnames << inflector.camelize(basename, abspath).to_sym
    abspaths << 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)

    unless collapse?(dir)
      cnames << inflector.camelize(basename, dir).to_sym
      abspaths << dir
    end
  end

  return unless root_namespace

  if cnames.empty?
    real_mod_name(root_namespace)
  else
    # We reverse before validating the segments to report the leftmost
    # problematic one, if any.
    cnames.reverse!

    cname_validator = Module.new
    cnames.each_with_index do |cname, i|
      cname_validator.const_defined?(cname, false)
    rescue ::NameError
      j = -(i + 1)
      raise Zeitwerk::NameError.new("cannot derive a constant name from #{abspaths[j]}")
    end

    if root_namespace == Object
      cnames.join("::")
    else
      "#{real_mod_name(root_namespace)}::#{cnames.join("::")}"
    end
  end
end

#reload ⇒ Object

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.

Raises:



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# File 'lib/zeitwerk/loader.rb', line 221

def reload
  raise ReloadingDisabledError unless reloading_enabled?
  raise SetupRequired unless @setup

  unload
  recompute_ignored_paths
  recompute_collapse_dirs
  setup
end

#setup ⇒ Object

Sets autoloads in the root namespaces.



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# File 'lib/zeitwerk/loader.rb', line 117

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

#unload ⇒ Object

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.



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# File 'lib/zeitwerk/loader.rb', line 143

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) ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/zeitwerk/loader.rb', line 298

def unloadable_cpath?(cpath)
  to_unload.key?(cpath)
end

#unloadable_cpaths ⇒ Object

Returns an array with the constant paths that would be unloaded on reload. This predicate returns an empty array if reloading is disabled.



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# File 'lib/zeitwerk/loader.rb', line 306

def unloadable_cpaths
  to_unload.keys.freeze
end

#unregister ⇒ Object

This is a dangerous method.



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# File 'lib/zeitwerk/loader.rb', line 314

def unregister
  Registry.unregister_loader(self)
  ExplicitNamespace.__unregister_loader(self)
end