class Zeitwerk::Loader
Attributes
@return [#call, debug, nil]
@private @return [Mutex]
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>]
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)}]
Absolute paths of files or directories not to be eager loaded.
@private @return [Set<String>]
Absolute paths of files, directories, of glob patterns to be totally ignored.
@private @return [Set<String>]
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>]
@return [#camelize]
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>}]
@return [#call, debug, nil]
@private @return [Mutex]
@private @return [Mutex]
Absolute paths of files or directories that have to be preloaded.
@private @return [<String>]
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}]
@return [String]
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
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 455 def all_dirs Registry.loaders.flat_map(&:dirs).freeze end
Broadcasts `eager_load` to all loaders.
@return [void]
# File lib/zeitwerk/loader.rb, line 447 def eager_load_all Registry.loaders.each(&:eager_load) end
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 439 def for_gem called_from = caller_locations(1, 1).first.path Registry.loader_for_gem(called_from) end
# File lib/zeitwerk/loader.rb, line 126 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
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 165 def dirs root_dirs.keys.freeze end
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 373 def do_not_eager_load(*paths) mutex.synchronize { eager_load_exclusions.merge(expand_paths(paths)) } end
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 336 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
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 193 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
Configure files, directories, or glob patterns to be totally ignored.
@param paths [<String, Pathname, <String, Pathname>>] @return [void]
# File lib/zeitwerk/loader.rb, line 227 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
Logs to `$stdout`, handy shortcut for debugging.
@return [void]
# File lib/zeitwerk/loader.rb, line 397 def log! @logger = ->(msg) { puts msg } end
@private @param dir [String] @return [Boolean]
# File lib/zeitwerk/loader.rb, line 404 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
Files or directories to be preloaded instead of lazy loaded.
@param paths [<String, Pathname, <String, Pathname>>] @return [void]
# File lib/zeitwerk/loader.rb, line 214 def preload(*paths) mutex.synchronize do expand_paths(paths).each do |abspath| preloads << abspath do_preload_abspath(abspath) if @setup end end end
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 178 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
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 320 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
@return [Boolean]
# File lib/zeitwerk/loader.rb, line 206 def reloading_enabled? @reloading_enabled end
Sets autoloads in the root namespace and preloads files, if any.
@return [void]
# File lib/zeitwerk/loader.rb, line 238 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
Sets a tag for the loader, useful for logging.
@return [void]
# File lib/zeitwerk/loader.rb, line 157 def tag=(tag) @tag = tag.to_s end
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 258 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
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 382 def unloadable_cpath?(cpath) to_unload.key?(cpath) end
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 390 def unloadable_cpaths to_unload.keys.freeze end