Class: Zeitwerk::Loader

Inherits:
Object
  • Object
show all
Includes:
Callbacks, RealModName
Defined in:
lib/zeitwerk/loader.rb

Defined Under Namespace

Modules: Callbacks

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from RealModName

#real_mod_name

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 143

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
  @collapse_glob_patterns = Set.new
  @collapse_dirs          = Set.new
  @autoloads              = {}
  @autoloaded_dirs        = []
  @to_unload              = {}
  @lazy_subdirs           = {}
  @eager_load_exclusions  = Set.new
  @on_load_callbacks      = {}

  # 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

Class Attribute Details

.default_logger ⇒ Object

Returns the value of attribute default_logger.



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# File 'lib/zeitwerk/loader.rb', line 481

def default_logger
  @default_logger
end

.mutex ⇒ Object 



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# File 'lib/zeitwerk/loader.rb', line 485

def mutex
  @mutex
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 90

def autoloaded_dirs
  @autoloaded_dirs
end

#autoloads ⇒ Object (readonly)

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]
...



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# File 'lib/zeitwerk/loader.rb', line 80

def autoloads
  @autoloads
end

#collapse_dirs ⇒ Object (readonly)

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



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# File 'lib/zeitwerk/loader.rb', line 68

def collapse_dirs
  @collapse_dirs
end

#collapse_glob_patterns ⇒ Object (readonly)

Absolute paths of directories or glob patterns to be collapsed.



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# File 'lib/zeitwerk/loader.rb', line 61

def collapse_glob_patterns
  @collapse_glob_patterns
end

#eager_load_exclusions ⇒ Object (readonly)

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



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# File 'lib/zeitwerk/loader.rb', line 130

def eager_load_exclusions
  @eager_load_exclusions
end

#ignored_glob_patterns ⇒ Object (readonly)

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



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# File 'lib/zeitwerk/loader.rb', line 47

def ignored_glob_patterns
  @ignored_glob_patterns
end

#ignored_paths ⇒ Object (readonly)

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.



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# File 'lib/zeitwerk/loader.rb', line 55

def ignored_paths
  @ignored_paths
end

#inflector ⇒ Object

Returns the value of attribute inflector.



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# File 'lib/zeitwerk/loader.rb', line 16

def inflector
  @inflector
end

#lazy_subdirs ⇒ Object (readonly)

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.



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# File 'lib/zeitwerk/loader.rb', line 124

def lazy_subdirs
  @lazy_subdirs
end

#logger ⇒ Object

Returns the value of attribute logger.



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# File 'lib/zeitwerk/loader.rb', line 19

def logger
  @logger
end

#mutex ⇒ Object (readonly) 



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# File 'lib/zeitwerk/loader.rb', line 137

def mutex
  @mutex
end

#mutex2 ⇒ Object (readonly) 



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# File 'lib/zeitwerk/loader.rb', line 141

def mutex2
  @mutex2
end

#on_load_callbacks ⇒ Object (readonly)

User-oriented callbacks to be fired when a constant is loaded.



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# File 'lib/zeitwerk/loader.rb', line 133

def on_load_callbacks
  @on_load_callbacks
end

#preloads ⇒ Object (readonly)

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



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# File 'lib/zeitwerk/loader.rb', line 40

def preloads
  @preloads
end

#root_dirs ⇒ Object (readonly)

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`.



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# File 'lib/zeitwerk/loader.rb', line 34

def root_dirs
  @root_dirs
end

#tag ⇒ Object

Returns the value of attribute tag.



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# File 'lib/zeitwerk/loader.rb', line 13

def tag
  @tag
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 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.



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# File 'lib/zeitwerk/loader.rb', line 106

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 515

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

.eager_load_all ⇒ Object

Broadcasts ‘eager_load` to all loaders.



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# File 'lib/zeitwerk/loader.rb', line 507

def eager_load_all
  Registry.loaders.each(&:eager_load)
end

.for_gem ⇒ 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.



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# File 'lib/zeitwerk/loader.rb', line 499

def for_gem
  called_from = caller_locations(1, 1).first.path
  Registry.loader_for_gem(called_from)
end

Instance Method Details

#collapse(*glob_patterns) ⇒ Object

Configure directories or glob patterns to be collapsed.



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# File 'lib/zeitwerk/loader.rb', line 261

def collapse(*glob_patterns)
  glob_patterns = expand_paths(glob_patterns)
  mutex.synchronize do
    collapse_glob_patterns.merge(glob_patterns)
    collapse_dirs.merge(expand_glob_patterns(glob_patterns))
  end
end

#dirs ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 186

def dirs
  root_dirs.keys.freeze
end

#do_not_eager_load(*paths) ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 435

def do_not_eager_load(*paths)
  mutex.synchronize { eager_load_exclusions.merge(expand_paths(paths)) }
end

#eager_load ⇒ Object

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`.



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# File 'lib/zeitwerk/loader.rb', line 392

def eager_load
  mutex.synchronize do
    break if @eager_loaded

    queue = []
    actual_root_dirs.each do |root_dir, namespace|
      queue << [namespace, root_dir] unless eager_load_exclusions.member?(root_dir)
    end

    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)
          if collapse_dirs.member?(abspath)
            queue << [namespace, abspath]
          else
            cname = inflector.camelize(basename, abspath)
            queue << [namespace.const_get(cname, false), abspath]
          end
        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 ⇒ Object

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.

Raises:



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# File 'lib/zeitwerk/loader.rb', line 218

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) ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 250

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! ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 458

def log!
  @logger = ->(msg) { puts msg }
end

#manages?(dir) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/zeitwerk/loader.rb', line 464

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

#on_load(cpath, &block) ⇒ Object

Configure a block to be invoked once a certain constant path is loaded. Supports multiple callbacks, and if there are many, they are executed in the order in which they were defined.

loader.on_load("SomeApiClient") do
  SomeApiClient.endpoint = "https://api.dev"
end

Raises:

  • (TypeError) 


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# File 'lib/zeitwerk/loader.rb', line 279

def on_load(cpath, &block)
  raise TypeError, "on_load only accepts strings" unless cpath.is_a?(String)

  mutex.synchronize do
    (on_load_callbacks[cpath] ||= []) << block
  end
end

#preload(*paths) ⇒ Object

Files or directories to be preloaded instead of lazy loaded.



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# File 'lib/zeitwerk/loader.rb', line 238

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, namespace: Object) ⇒ Object

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.

Raises:



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# File 'lib/zeitwerk/loader.rb', line 198

def push_dir(path, namespace: Object)
  # Note that Class < Module.
  unless namespace.is_a?(Module)
    raise Error, "#{namespace.inspect} is not a class or module object, should be"
  end

  abspath = File.expand_path(path)
  if dir?(abspath)
    raise_if_conflicting_directory(abspath)
    root_dirs[abspath] = namespace
  else
    raise Error, "the root directory #{abspath} does not exist"
  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 375

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

#reloading_enabled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/zeitwerk/loader.rb', line 231

def reloading_enabled?
  @reloading_enabled
end

#setup ⇒ Object

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



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# File 'lib/zeitwerk/loader.rb', line 290

def setup
  mutex.synchronize do
    break if @setup

    actual_root_dirs.each do |root_dir, namespace|
      set_autoloads_in_dir(root_dir, namespace)
    end
    do_preload

    @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.



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# File 'lib/zeitwerk/loader.rb', line 312

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
    @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 443

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 451

def unloadable_cpaths
  to_unload.keys.freeze
end