lib/active_support/dependencies.rb in activesupport-3.2.22.5 vs lib/active_support/dependencies.rb in activesupport-4.0.0.beta1

@@ -1,7 +1,8 @@
 require 'set'
 require 'thread'
+require 'thread_safe'
 require 'pathname'
 require 'active_support/core_ext/module/aliasing'
 require 'active_support/core_ext/module/attribute_accessors'
 require 'active_support/core_ext/module/introspection'
 require 'active_support/core_ext/module/anonymous'
@@ -41,44 +42,47 @@
     # The set of directories from which automatically loaded constants are loaded
     # only once. All directories in this set must also be present in +autoload_paths+.
     mattr_accessor :autoload_once_paths
     self.autoload_once_paths = []
 
-    # An array of qualified constant names that have been loaded. Adding a name to
-    # this array will cause it to be unloaded the next time Dependencies are cleared.
+    # An array of qualified constant names that have been loaded. Adding a name
+    # to this array will cause it to be unloaded the next time Dependencies are
+    # cleared.
     mattr_accessor :autoloaded_constants
     self.autoloaded_constants = []
 
     # An array of constant names that need to be unloaded on every request. Used
     # to allow arbitrary constants to be marked for unloading.
     mattr_accessor :explicitly_unloadable_constants
     self.explicitly_unloadable_constants = []
 
-    # The logger is used for generating information on the action run-time (including benchmarking) if available.
-    # Can be set to nil for no logging. Compatible with both Ruby's own Logger and Log4r loggers.
+    # The logger is used for generating information on the action run-time
+    # (including benchmarking) if available. Can be set to nil for no logging.
+    # Compatible with both Ruby's own Logger and Log4r loggers.
     mattr_accessor :logger
 
-    # Set to true to enable logging of const_missing and file loads
+    # Set to +true+ to enable logging of const_missing and file loads.
     mattr_accessor :log_activity
     self.log_activity = false
 
-    # The WatchStack keeps a stack of the modules being watched as files are loaded.
-    # If a file in the process of being loaded (parent.rb) triggers the load of
-    # another file (child.rb) the stack will ensure that child.rb handles the new
-    # constants.
+    # The WatchStack keeps a stack of the modules being watched as files are
+    # loaded. If a file in the process of being loaded (parent.rb) triggers the
+    # load of another file (child.rb) the stack will ensure that child.rb
+    # handles the new constants.
     #
     # If child.rb is being autoloaded, its constants will be added to
     # autoloaded_constants. If it was being `require`d, they will be discarded.
     #
     # This is handled by walking back up the watch stack and adding the constants
-    # found by child.rb to the list of original constants in parent.rb
+    # found by child.rb to the list of original constants in parent.rb.
     class WatchStack
       include Enumerable
 
       # @watching is a stack of lists of constants being watched. For instance,
-      # if parent.rb is autoloaded, the stack will look like [[Object]]. If parent.rb
-      # then requires namespace/child.rb, the stack will look like [[Object], [Namespace]].
+      # if parent.rb is autoloaded, the stack will look like [[Object]]. If
+      # parent.rb then requires namespace/child.rb, the stack will look like
+      # [[Object], [Namespace]].
 
       def initialize
         @watching = []
         @stack = Hash.new { |h,k| h[k] = [] }
       end
@@ -89,11 +93,12 @@
 
       def watching?
         !@watching.empty?
       end
 
-      # return a list of new constants found since the last call to watch_namespaces
+      # Returns a list of new constants found since the last call to
+      # <tt>watch_namespaces</tt>.
       def new_constants
         constants = []
 
         # Grab the list of namespaces that we're looking for new constants under
         @watching.last.each do |namespace|
@@ -103,11 +108,11 @@
 
           mod = Inflector.constantize(namespace) if Dependencies.qualified_const_defined?(namespace)
           next unless mod.is_a?(Module)
 
           # Get a list of the constants that were added
-          new_constants = mod.local_constant_names - original_constants
+          new_constants = mod.local_constants - original_constants
 
           # self[namespace] returns an Array of the constants that are being evaluated
           # for that namespace. For instance, if parent.rb requires child.rb, the first
           # element of self[Object] will be an Array of the constants that were present
           # before parent.rb was required. The second element will be an Array of the
@@ -125,22 +130,21 @@
       ensure
         # A call to new_constants is always called after a call to watch_namespaces
         pop_modules(@watching.pop)
       end
 
-      # Add a set of modules to the watch stack, remembering the initial constants
+      # Add a set of modules to the watch stack, remembering the initial
+      # constants.
       def watch_namespaces(namespaces)
-        watching = []
-        namespaces.map do |namespace|
+        @watching << namespaces.map do |namespace|
           module_name = Dependencies.to_constant_name(namespace)
           original_constants = Dependencies.qualified_const_defined?(module_name) ?
-            Inflector.constantize(module_name).local_constant_names : []
+            Inflector.constantize(module_name).local_constants : []
 
-          watching << module_name
           @stack[module_name] << original_constants
+          module_name
         end
-        @watching << watching
       end
 
       private
       def pop_modules(modules)
         modules.each { |mod| @stack[mod].pop }
@@ -149,11 +153,11 @@
 
     # An internal stack used to record which constants are loaded by any block.
     mattr_accessor :constant_watch_stack
     self.constant_watch_stack = WatchStack.new
 
-    # Module includes this module
+    # Module includes this module.
     module ModuleConstMissing #:nodoc:
       def self.append_features(base)
         base.class_eval do
           # Emulate #exclude via an ivar
           return if defined?(@_const_missing) && @_const_missing
@@ -168,48 +172,25 @@
           define_method :const_missing, @_const_missing
           @_const_missing = nil
         end
       end
 
-      # Use const_missing to autoload associations so we don't have to
-      # require_association when using single-table inheritance.
-      def const_missing(const_name, nesting = nil)
-        klass_name = name.presence || "Object"
-
-        unless nesting
-          # We'll assume that the nesting of Foo::Bar is ["Foo::Bar", "Foo"]
-          # even though it might not be, such as in the case of
-          # class Foo::Bar; Baz; end
-          nesting = []
-          klass_name.to_s.scan(/::|$/) { nesting.unshift $` }
-        end
-
-        # If there are multiple levels of nesting to search under, the top
-        # level is the one we want to report as the lookup fail.
-        error = nil
-
-        nesting.each do |namespace|
-          begin
-            return Dependencies.load_missing_constant Inflector.constantize(namespace), const_name
-          rescue NoMethodError then raise
-          rescue NameError => e
-            error ||= e
-          end
-        end
-
-        # Raise the first error for this set. If this const_missing came from an
-        # earlier const_missing, this will result in the real error bubbling
-        # all the way up
-        raise error
+      def const_missing(const_name)
+        # The interpreter does not pass nesting information, and in the
+        # case of anonymous modules we cannot even make the trade-off of
+        # assuming their name reflects the nesting. Resort to Object as
+        # the only meaningful guess we can make.
+        from_mod = anonymous? ? ::Object : self
+        Dependencies.load_missing_constant(from_mod, const_name)
       end
 
       def unloadable(const_desc = self)
         super(const_desc)
       end
     end
 
-    # Object includes this module
+    # Object includes this module.
     module Loadable #:nodoc:
       def self.exclude_from(base)
         base.class_eval { define_method(:load, Kernel.instance_method(:load)) }
       end
 
@@ -220,17 +201,13 @@
       def require_dependency(file_name, message = "No such file to load -- %s")
         unless file_name.is_a?(String)
           raise ArgumentError, "the file name must be a String -- you passed #{file_name.inspect}"
         end
 
-        Dependencies.depend_on(file_name, false, message)
+        Dependencies.depend_on(file_name, message)
       end
 
-      def require_association(file_name)
-        Dependencies.associate_with(file_name)
-      end
-
       def load_dependency(file)
         if Dependencies.load? && ActiveSupport::Dependencies.constant_watch_stack.watching?
           Dependencies.new_constants_in(Object) { yield }
         else
           yield
@@ -250,29 +227,29 @@
         result = false
         load_dependency(file) { result = super }
         result
       end
 
-      # Mark the given constant as unloadable. Unloadable constants are removed each
-      # time dependencies are cleared.
+      # Mark the given constant as unloadable. Unloadable constants are removed
+      # each time dependencies are cleared.
       #
       # Note that marking a constant for unloading need only be done once. Setup
       # or init scripts may list each unloadable constant that may need unloading;
-      # each constant will be removed for every subsequent clear, as opposed to for
-      # the first clear.
+      # each constant will be removed for every subsequent clear, as opposed to
+      # for the first clear.
       #
       # The provided constant descriptor may be a (non-anonymous) module or class,
       # or a qualified constant name as a string or symbol.
       #
-      # Returns true if the constant was not previously marked for unloading, false
-      # otherwise.
+      # Returns +true+ if the constant was not previously marked for unloading,
+      # +false+ otherwise.
       def unloadable(const_desc)
         Dependencies.mark_for_unload const_desc
       end
     end
 
-    # Exception file-blaming
+    # Exception file-blaming.
     module Blamable #:nodoc:
       def blame_file!(file)
         (@blamed_files ||= []).unshift file
       end
 
@@ -293,48 +270,41 @@
 
     def hook!
       Object.class_eval { include Loadable }
       Module.class_eval { include ModuleConstMissing }
       Exception.class_eval { include Blamable }
-      true
     end
 
     def unhook!
       ModuleConstMissing.exclude_from(Module)
       Loadable.exclude_from(Object)
-      true
     end
 
     def load?
       mechanism == :load
     end
 
-    def depend_on(file_name, swallow_load_errors = false, message = "No such file to load -- %s.rb")
+    def depend_on(file_name, message = "No such file to load -- %s.rb")
       path = search_for_file(file_name)
       require_or_load(path || file_name)
     rescue LoadError => load_error
-      unless swallow_load_errors
-        if file_name = load_error.message[/ -- (.*?)(\.rb)?$/, 1]
-          raise LoadError.new(message % file_name).copy_blame!(load_error)
-        end
-        raise
+      if file_name = load_error.message[/ -- (.*?)(\.rb)?$/, 1]
+        load_error.message.replace(message % file_name)
+        load_error.copy_blame!(load_error)
       end
+      raise
     end
 
-    def associate_with(file_name)
-      depend_on(file_name, true)
-    end
-
     def clear
       log_call
       loaded.clear
       remove_unloadable_constants!
     end
 
     def require_or_load(file_name, const_path = nil)
       log_call file_name, const_path
-      file_name = $1 if file_name =~ /^(.*)\.rb$/
+      file_name = $` if file_name =~ /\.rb\z/
       expanded = File.expand_path(file_name)
       return if loaded.include?(expanded)
 
       # Record that we've seen this file *before* loading it to avoid an
       # infinite loop with mutual dependencies.
@@ -363,40 +333,23 @@
         raise
       end
 
       # Record history *after* loading so first load gets warnings.
       history << expanded
-      return result
+      result
     end
 
     # Is the provided constant path defined?
-    if Module.method(:const_defined?).arity == 1
-      def qualified_const_defined?(path)
-        Object.qualified_const_defined?(path.sub(/^::/, ''))
-      end
-    else
-      def qualified_const_defined?(path)
-        Object.qualified_const_defined?(path.sub(/^::/, ''), false)
-      end
+    def qualified_const_defined?(path)
+      Object.qualified_const_defined?(path.sub(/^::/, ''), false)
     end
 
-    if Module.method(:const_defined?).arity == 1
-      # Does this module define this constant?
-      # Wrapper to accommodate changing Module#const_defined? in Ruby 1.9
-      def local_const_defined?(mod, const)
-        mod.const_defined?(const)
-      end
-    else
-      def local_const_defined?(mod, const) #:nodoc:
-        mod.const_defined?(const, false)
-      end
-    end
-
-    # Given +path+, a filesystem path to a ruby file, return an array of constant
-    # paths which would cause Dependencies to attempt to load this file.
+    # Given +path+, a filesystem path to a ruby file, return an array of
+    # constant paths which would cause Dependencies to attempt to load this
+    # file.
     def loadable_constants_for_path(path, bases = autoload_paths)
-      path = $1 if path =~ /\A(.*)\.rb\Z/
+      path = $` if path =~ /\.rb\z/
       expanded_path = File.expand_path(path)
       paths = []
 
       bases.each do |root|
         expanded_root = File.expand_path(root)
@@ -423,11 +376,12 @@
       end
       nil # Gee, I sure wish we had first_match ;-)
     end
 
     # Does the provided path_suffix correspond to an autoloadable module?
-    # Instead of returning a boolean, the autoload base for this module is returned.
+    # Instead of returning a boolean, the autoload base for this module is
+    # returned.
     def autoloadable_module?(path_suffix)
       autoload_paths.each do |load_path|
         return load_path if File.directory? File.join(load_path, path_suffix)
       end
       nil
@@ -437,91 +391,117 @@
       # to_s works around a ruby1.9 issue where #starts_with?(Pathname) will always return false
       autoload_once_paths.any? { |base| path.starts_with? base.to_s }
     end
 
     # Attempt to autoload the provided module name by searching for a directory
-    # matching the expected path suffix. If found, the module is created and assigned
-    # to +into+'s constants with the name +const_name+. Provided that the directory
-    # was loaded from a reloadable base path, it is added to the set of constants
-    # that are to be unloaded.
+    # matching the expected path suffix. If found, the module is created and
+    # assigned to +into+'s constants with the name +const_name+. Provided that
+    # the directory was loaded from a reloadable base path, it is added to the
+    # set of constants that are to be unloaded.
     def autoload_module!(into, const_name, qualified_name, path_suffix)
       return nil unless base_path = autoloadable_module?(path_suffix)
       mod = Module.new
       into.const_set const_name, mod
       autoloaded_constants << qualified_name unless autoload_once_paths.include?(base_path)
-      return mod
+      mod
     end
 
     # Load the file at the provided path. +const_paths+ is a set of qualified
     # constant names. When loading the file, Dependencies will watch for the
     # addition of these constants. Each that is defined will be marked as
     # autoloaded, and will be removed when Dependencies.clear is next called.
     #
-    # If the second parameter is left off, then Dependencies will construct a set
-    # of names that the file at +path+ may define. See
+    # If the second parameter is left off, then Dependencies will construct a
+    # set of names that the file at +path+ may define. See
     # +loadable_constants_for_path+ for more details.
     def load_file(path, const_paths = loadable_constants_for_path(path))
       log_call path, const_paths
       const_paths = [const_paths].compact unless const_paths.is_a? Array
-      parent_paths = const_paths.collect { |const_path| /(.*)::[^:]+\Z/ =~ const_path ? $1 : :Object }
+      parent_paths = const_paths.collect { |const_path| const_path[/.*(?=::)/] || :Object }
 
       result = nil
       newly_defined_paths = new_constants_in(*parent_paths) do
         result = Kernel.load path
       end
 
       autoloaded_constants.concat newly_defined_paths unless load_once_path?(path)
       autoloaded_constants.uniq!
       log "loading #{path} defined #{newly_defined_paths * ', '}" unless newly_defined_paths.empty?
-      return result
+      result
     end
 
-    # Return the constant path for the provided parent and constant name.
+    # Returns the constant path for the provided parent and constant name.
     def qualified_name_for(mod, name)
       mod_name = to_constant_name mod
       mod_name == "Object" ? name.to_s : "#{mod_name}::#{name}"
     end
 
     # Load the constant named +const_name+ which is missing from +from_mod+. If
-    # it is not possible to load the constant into from_mod, try its parent module
-    # using const_missing.
+    # it is not possible to load the constant into from_mod, try its parent
+    # module using +const_missing+.
     def load_missing_constant(from_mod, const_name)
       log_call from_mod, const_name
 
       unless qualified_const_defined?(from_mod.name) && Inflector.constantize(from_mod.name).equal?(from_mod)
         raise ArgumentError, "A copy of #{from_mod} has been removed from the module tree but is still active!"
       end
 
-      raise NameError, "#{from_mod} is not missing constant #{const_name}!" if local_const_defined?(from_mod, const_name)
+      raise NameError, "#{from_mod} is not missing constant #{const_name}!" if from_mod.const_defined?(const_name, false)
 
       qualified_name = qualified_name_for from_mod, const_name
       path_suffix = qualified_name.underscore
 
       file_path = search_for_file(path_suffix)
 
-      if file_path && ! loaded.include?(File.expand_path(file_path).sub(/\.rb\z/, '')) # We found a matching file to load
-        require_or_load file_path
-        raise LoadError, "Expected #{file_path} to define #{qualified_name}" unless local_const_defined?(from_mod, const_name)
-        return from_mod.const_get(const_name)
+      if file_path
+        expanded = File.expand_path(file_path)
+        expanded.sub!(/\.rb\z/, '')
+
+        if loaded.include?(expanded)
+          raise "Circular dependency detected while autoloading constant #{qualified_name}"
+        else
+          require_or_load(expanded)
+          raise LoadError, "Unable to autoload constant #{qualified_name}, expected #{file_path} to define it" unless from_mod.const_defined?(const_name, false)
+          return from_mod.const_get(const_name)
+        end
       elsif mod = autoload_module!(from_mod, const_name, qualified_name, path_suffix)
         return mod
       elsif (parent = from_mod.parent) && parent != from_mod &&
-            ! from_mod.parents.any? { |p| local_const_defined?(p, const_name) }
+            ! from_mod.parents.any? { |p| p.const_defined?(const_name, false) }
         # If our parents do not have a constant named +const_name+ then we are free
         # to attempt to load upwards. If they do have such a constant, then this
         # const_missing must be due to from_mod::const_name, which should not
         # return constants from from_mod's parents.
         begin
+          # Since Ruby does not pass the nesting at the point the unknown
+          # constant triggered the callback we cannot fully emulate constant
+          # name lookup and need to make a trade-off: we are going to assume
+          # that the nesting in the body of Foo::Bar is [Foo::Bar, Foo] even
+          # though it might not be. Counterexamples are
+          #
+          #   class Foo::Bar
+          #     Module.nesting # => [Foo::Bar]
+          #   end
+          #
+          # or
+          #
+          #   module M::N
+          #     module S::T
+          #       Module.nesting # => [S::T, M::N]
+          #     end
+          #   end
+          #
+          # for example.
           return parent.const_missing(const_name)
         rescue NameError => e
           raise unless e.missing_name? qualified_name_for(parent, const_name)
         end
       end
 
       raise NameError,
             "uninitialized constant #{qualified_name}",
-            caller.reject {|l| l.starts_with? __FILE__ }
+            caller.reject { |l| l.starts_with? __FILE__ }
     end
 
     # Remove the constants that have been autoloaded, and those that have been
     # marked for unloading. Before each constant is removed a callback is sent
     # to its class/module if it implements +before_remove_const+.
@@ -536,11 +516,11 @@
       explicitly_unloadable_constants.each { |const| remove_constant const }
     end
 
     class ClassCache
       def initialize
-        @store = Hash.new
+        @store = ThreadSafe::Cache.new
       end
 
       def empty?
         @store.empty?
       end
@@ -555,14 +535,11 @@
       end
       alias :[] :get
 
       def safe_get(key)
         key = key.name if key.respond_to?(:name)
-        @store[key] || begin
-          klass = Inflector.safe_constantize(key)
-          @store[key] = klass
-        end
+        @store[key] ||= Inflector.safe_constantize(key)
       end
 
       def store(klass)
         return self unless klass.respond_to?(:name)
         raise(ArgumentError, 'anonymous classes cannot be cached') if klass.name.empty?
@@ -587,18 +564,17 @@
     def constantize(name)
       Reference.get(name)
     end
 
     # Get the reference for class named +name+ if one exists.
-    # Otherwise returns nil.
+    # Otherwise returns +nil+.
     def safe_constantize(name)
       Reference.safe_get(name)
     end
 
     # Determine if the given constant has been automatically loaded.
     def autoloaded?(desc)
-      # No name => anonymous module.
       return false if desc.is_a?(Module) && desc.anonymous?
       name = to_constant_name desc
       return false unless qualified_const_defined? name
       return autoloaded_constants.include?(name)
     end
@@ -612,14 +588,14 @@
     # Mark the provided constant name for unloading. This constant will be
     # unloaded on each request, not just the next one.
     def mark_for_unload(const_desc)
       name = to_constant_name const_desc
       if explicitly_unloadable_constants.include? name
-        return false
+        false
       else
         explicitly_unloadable_constants << name
-        return true
+        true
       end
     end
 
     # Run the provided block and detect the new constants that were loaded during
     # its execution. Constants may only be regarded as 'new' once -- so if the
@@ -643,14 +619,14 @@
 
         log "New constants: #{new_constants * ', '}"
         return new_constants unless aborting
 
         log "Error during loading, removing partially loaded constants "
-        new_constants.each {|c| remove_constant(c) }.clear
+        new_constants.each { |c| remove_constant(c) }.clear
       end
 
-      return []
+      []
     end
 
     # Convert the provided const desc to a qualified constant name (as a string).
     # A module, class, symbol, or string may be provided.
     def to_constant_name(desc) #:nodoc:
@@ -663,22 +639,65 @@
         else raise TypeError, "Not a valid constant descriptor: #{desc.inspect}"
       end
     end
 
     def remove_constant(const) #:nodoc:
-      return false unless qualified_const_defined? const
+      # Normalize ::Foo, ::Object::Foo, Object::Foo, Object::Object::Foo, etc. as Foo.
+      normalized = const.to_s.sub(/\A::/, '')
+      normalized.sub!(/\A(Object::)+/, '')
 
-      # Normalize ::Foo, Foo, Object::Foo, and ::Object::Foo to Object::Foo
-      names = const.to_s.sub(/^::(Object)?/, 'Object::').split("::")
-      to_remove = names.pop
-      parent = Inflector.constantize(names * '::')
+      constants = normalized.split('::')
+      to_remove = constants.pop
 
+      if constants.empty?
+        parent = Object
+      else
+        # This method is robust to non-reachable constants.
+        #
+        # Non-reachable constants may be passed if some of the parents were
+        # autoloaded and already removed. It is easier to do a sanity check
+        # here than require the caller to be clever. We check the parent
+        # rather than the very const argument because we do not want to
+        # trigger Kernel#autoloads, see the comment below.
+        parent_name = constants.join('::')
+        return unless qualified_const_defined?(parent_name)
+        parent = constantize(parent_name)
+      end
+
       log "removing constant #{const}"
-      constantized = constantize(const)
-      constantized.before_remove_const if constantized.respond_to?(:before_remove_const)
-      parent.instance_eval { remove_const to_remove }
 
-      return true
+      # In an autoloaded user.rb like this
+      #
+      #   autoload :Foo, 'foo'
+      #
+      #   class User < ActiveRecord::Base
+      #   end
+      #
+      # we correctly register "Foo" as being autoloaded. But if the app does
+      # not use the "Foo" constant we need to be careful not to trigger
+      # loading "foo.rb" ourselves. While #const_defined? and #const_get? do
+      # require the file, #autoload? and #remove_const don't.
+      #
+      # We are going to remove the constant nonetheless ---which exists as
+      # far as Ruby is concerned--- because if the user removes the macro
+      # call from a class or module that were not autoloaded, as in the
+      # example above with Object, accessing to that constant must err.
+      unless parent.autoload?(to_remove)
+        begin
+          constantized = parent.const_get(to_remove, false)
+        rescue NameError
+          log "the constant #{const} is not reachable anymore, skipping"
+          return
+        else
+          constantized.before_remove_const if constantized.respond_to?(:before_remove_const)
+        end
+      end
+
+      begin
+        parent.instance_eval { remove_const to_remove }
+      rescue NameError
+        log "the constant #{const} is not reachable anymore, skipping"
+      end
     end
 
     protected
       def log_call(*args)
         if log_activity?