aboutsummaryrefslogtreecommitdiffstats
path: root/activesupport/lib/active_support/dependencies.rb
blob: 2badad5f5f53f4f9e626375f3699d5fc710e0ea6 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
module ActiveSupport #:nodoc:
  module Dependencies #:nodoc:
    extend self

    # Should we turn on Ruby warnings on the first load of dependent files?
    mattr_accessor :warnings_on_first_load
    self.warnings_on_first_load = false

    # All files ever loaded.
    mattr_accessor :history
    self.history = Set.new

    # All files currently loaded.
    mattr_accessor :loaded
    self.loaded = Set.new

    # Should we load files or require them?
    mattr_accessor :mechanism
    self.mechanism = :load

    # The set of directories from which we may automatically load files. Files
    # under these directories will be reloaded on each request in development mode,
    # unless the directory also appears in load_once_paths.
    mattr_accessor :load_paths
    self.load_paths = []

    # The set of directories from which automatically loaded constants are loaded
    # only once. All directories in this set must also be present in +load_paths+.
    mattr_accessor :load_once_paths
    self.load_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.
    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.
    mattr_accessor :logger

    # Set to true to enable logging of const_missing and file loads
    mattr_accessor :log_activity
    self.log_activity = false

    # An internal stack used to record which constants are loaded by any block.
    mattr_accessor :constant_watch_stack
    self.constant_watch_stack = []

    mattr_accessor :constant_watch_stack_mutex
    self.constant_watch_stack_mutex = Mutex.new

    # Module includes this module
    module ModuleConstMissing #:nodoc:
      def self.included(base) #:nodoc:
        base.class_eval do
          unless defined? const_missing_without_dependencies
            alias_method_chain :const_missing, :dependencies
          end
        end
      end

      def self.excluded(base) #:nodoc:
        base.class_eval do
          if defined? const_missing_without_dependencies
            undef_method :const_missing
            alias_method :const_missing, :const_missing_without_dependencies
            undef_method :const_missing_without_dependencies
          end
        end
      end

      # Use const_missing to autoload associations so we don't have to
      # require_association when using single-table inheritance.
      def const_missing_with_dependencies(class_id)
        ActiveSupport::Dependencies.load_missing_constant self, class_id
      end

      def unloadable(const_desc = self)
        super(const_desc)
      end
    end

    # Class includes this module
    module ClassConstMissing #:nodoc:
      def const_missing(const_name)
        if [Object, Kernel].include?(self) || parent == self
          super
        else
          begin
            begin
              Dependencies.load_missing_constant self, const_name
            rescue NameError
              parent.send :const_missing, const_name
            end
          rescue NameError => e
            # Make sure that the name we are missing is the one that caused the error
            parent_qualified_name = Dependencies.qualified_name_for parent, const_name
            raise unless e.missing_name? parent_qualified_name
            qualified_name = Dependencies.qualified_name_for self, const_name
            raise NameError.new("uninitialized constant #{qualified_name}").copy_blame!(e)
          end
        end
      end
    end

    # Object includes this module
    module Loadable #:nodoc:
      def self.included(base) #:nodoc:
        base.class_eval do
          unless defined? load_without_new_constant_marking
            alias_method_chain :load, :new_constant_marking
          end
        end
      end

      def self.excluded(base) #:nodoc:
        base.class_eval do
          if defined? load_without_new_constant_marking
            undef_method :load
            alias_method :load, :load_without_new_constant_marking
            undef_method :load_without_new_constant_marking
          end
        end
      end

      def require_or_load(file_name)
        Dependencies.require_or_load(file_name)
      end

      def require_dependency(file_name)
        Dependencies.depend_on(file_name)
      end

      def require_association(file_name)
        Dependencies.associate_with(file_name)
      end

      def load_with_new_constant_marking(file, *extras) #:nodoc:
        if Dependencies.load?
          Dependencies.new_constants_in(Object) { load_without_new_constant_marking(file, *extras) }
        else
          load_without_new_constant_marking(file, *extras)
        end
      rescue Exception => exception  # errors from loading file
        exception.blame_file! file
        raise
      end

      def require(file, *extras) #:nodoc:
        if Dependencies.load?
          Dependencies.new_constants_in(Object) { super }
        else
          super
        end
      rescue Exception => exception  # errors from required file
        exception.blame_file! file
        raise
      end

      # 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.
      #
      # 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.
      def unloadable(const_desc)
        Dependencies.mark_for_unload const_desc
      end
    end

    # Exception file-blaming
    module Blamable #:nodoc:
      def blame_file!(file)
        (@blamed_files ||= []).unshift file
      end

      def blamed_files
        @blamed_files ||= []
      end

      def describe_blame
        return nil if blamed_files.empty?
        "This error occurred while loading the following files:\n   #{blamed_files.join "\n   "}"
      end

      def copy_blame!(exc)
        @blamed_files = exc.blamed_files.clone
        self
      end
    end

    def hook!
      Object.instance_eval { include Loadable }
      Module.instance_eval { include ModuleConstMissing }
      Class.instance_eval { include ClassConstMissing }
      Exception.instance_eval { include Blamable }
      true
    end

    def unhook!
      ModuleConstMissing.excluded(Module)
      Loadable.excluded(Object)
      true
    end

    def load?
      mechanism == :load
    end

    def depend_on(file_name, swallow_load_errors = false)
      path = search_for_file(file_name)
      require_or_load(path || file_name)
    rescue LoadError
      raise unless swallow_load_errors
    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 = $1 if file_name =~ /^(.*)\.rb$/
      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.
      loaded << expanded

      begin
        if load?
          log "loading #{file_name}"

          # Enable warnings iff this file has not been loaded before and
          # warnings_on_first_load is set.
          load_args = ["#{file_name}.rb"]
          load_args << const_path unless const_path.nil?

          if !warnings_on_first_load or history.include?(expanded)
            result = load_file(*load_args)
          else
            enable_warnings { result = load_file(*load_args) }
          end
        else
          log "requiring #{file_name}"
          result = require file_name
        end
      rescue Exception
        loaded.delete expanded
        raise
      end

      # Record history *after* loading so first load gets warnings.
      history << expanded
      return result
    end

    # Is the provided constant path defined?
    def qualified_const_defined?(path)
      raise NameError, "#{path.inspect} is not a valid constant name!" unless
        /^(::)?([A-Z]\w*)(::[A-Z]\w*)*$/ =~ path

      names = path.to_s.split('::')
      names.shift if names.first.empty?

      # We can't use defined? because it will invoke const_missing for the parent
      # of the name we are checking.
      names.inject(Object) do |mod, name|
        return false unless uninherited_const_defined?(mod, name)
        mod.const_get name
      end
      return true
    end

    if Module.method(:const_defined?).arity == 1
      # Does this module define this constant?
      # Wrapper to accomodate changing Module#const_defined? in Ruby 1.9
      def uninherited_const_defined?(mod, const)
        mod.const_defined?(const)
      end
    else
      def uninherited_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.
    def loadable_constants_for_path(path, bases = load_paths)
      path = $1 if path =~ /\A(.*)\.rb\Z/
      expanded_path = File.expand_path(path)

      bases.collect do |root|
        expanded_root = File.expand_path(root)
        next unless %r{\A#{Regexp.escape(expanded_root)}(/|\\)} =~ expanded_path

        nesting = expanded_path[(expanded_root.size)..-1]
        nesting = nesting[1..-1] if nesting && nesting[0] == ?/
        next if nesting.blank?
        nesting_camel = nesting.camelize
        begin
          qualified_const_defined?(nesting_camel)
        rescue NameError
          next
        end
        [ nesting_camel ]
      end.flatten.compact.uniq
    end

    # Search for a file in load_paths matching the provided suffix.
    def search_for_file(path_suffix)
      path_suffix = path_suffix + '.rb' unless path_suffix.ends_with? '.rb'
      load_paths.each do |root|
        path = File.join(root, path_suffix)
        return path if File.file? path
      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.
    def autoloadable_module?(path_suffix)
      load_paths.each do |load_path|
        return load_path if File.directory? File.join(load_path, path_suffix)
      end
      nil
    end

    def load_once_path?(path)
      load_once_paths.any? { |base| path.starts_with? base }
    end

    # Attempt to autoload the provided module name by searching for a directory
    # matching the expect 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 load_once_paths.include?(base_path)
      return 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
    # +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 }

      result = nil
      newly_defined_paths = new_constants_in(*parent_paths) do
        result = load_without_new_constant_marking 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
    end

    # Return the constant path for the provided parent and constant name.
    def qualified_name_for(mod, name)
      mod_name = to_constant_name mod
      (%w(Object Kernel).include? mod_name) ? 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.
    def load_missing_constant(from_mod, const_name)
      log_call from_mod, const_name
      if from_mod == Kernel
        if ::Object.const_defined?(const_name)
          log "Returning Object::#{const_name} for Kernel::#{const_name}"
          return ::Object.const_get(const_name)
        else
          log "Substituting Object for Kernel"
          from_mod = Object
        end
      end

      # If we have an anonymous module, all we can do is attempt to load from Object.
      from_mod = Object if from_mod.name.blank?

      unless qualified_const_defined?(from_mod.name) && from_mod.name.constantize.object_id == from_mod.object_id
        raise ArgumentError, "A copy of #{from_mod} has been removed from the module tree but is still active!"
      end

      raise ArgumentError, "#{from_mod} is not missing constant #{const_name}!" if uninherited_const_defined?(from_mod, const_name)

      qualified_name = qualified_name_for from_mod, const_name
      path_suffix = qualified_name.underscore
      name_error = NameError.new("uninitialized constant #{qualified_name}")

      file_path = search_for_file(path_suffix)
      if file_path && ! loaded.include?(File.expand_path(file_path)) # We found a matching file to load
        require_or_load file_path
        raise LoadError, "Expected #{file_path} to define #{qualified_name}" unless uninherited_const_defined?(from_mod, const_name)
        return from_mod.const_get(const_name)
      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| uninherited_const_defined?(p, const_name) }
        # 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
          return parent.const_missing(const_name)
        rescue NameError => e
          raise unless e.missing_name? qualified_name_for(parent, const_name)
          raise name_error
        end
      else
        raise name_error
      end
    end

    # Remove the constants that have been autoloaded, and those that have been
    # marked for unloading.
    def remove_unloadable_constants!
      autoloaded_constants.each { |const| remove_constant const }
      autoloaded_constants.clear
      explicitly_unloadable_constants.each { |const| remove_constant const }
    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.name.blank?
      name = to_constant_name desc
      return false unless qualified_const_defined? name
      return autoloaded_constants.include?(name)
    end

    # Will the provided constant descriptor be unloaded?
    def will_unload?(const_desc)
      autoloaded?(const_desc) ||
        explicitly_unloadable_constants.include?(to_constant_name(const_desc))
    end

    # 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
      else
        explicitly_unloadable_constants << name
        return 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
    # block calls +new_constants_in+ again, then the constants defined within the
    # inner call will not be reported in this one.
    #
    # If the provided block does not run to completion, and instead raises an
    # exception, any new constants are regarded as being only partially defined
    # and will be removed immediately.
    def new_constants_in(*descs)
      log_call(*descs)

      # Build the watch frames. Each frame is a tuple of
      #   [module_name_as_string, constants_defined_elsewhere]
      watch_frames = descs.collect do |desc|
        if desc.is_a? Module
          mod_name = desc.name
          initial_constants = desc.local_constant_names
        elsif desc.is_a?(String) || desc.is_a?(Symbol)
          mod_name = desc.to_s

          # Handle the case where the module has yet to be defined.
          initial_constants = if qualified_const_defined?(mod_name)
            mod_name.constantize.local_constant_names
          else
            []
          end
        else
          raise Argument, "#{desc.inspect} does not describe a module!"
        end

        [mod_name, initial_constants]
      end

      constant_watch_stack_mutex.synchronize do
        constant_watch_stack.concat watch_frames
      end

      aborting = true
      begin
        yield # Now yield to the code that is to define new constants.
        aborting = false
      ensure
        # Find the new constants.
        new_constants = watch_frames.collect do |mod_name, prior_constants|
          # Module still doesn't exist? Treat it as if it has no constants.
          next [] unless qualified_const_defined?(mod_name)

          mod = mod_name.constantize
          next [] unless mod.is_a? Module
          new_constants = mod.local_constant_names - prior_constants

          # Make sure no other frames takes credit for these constants.
          constant_watch_stack_mutex.synchronize do
            constant_watch_stack.each do |frame_name, constants|
              constants.concat new_constants if frame_name == mod_name
            end
          end

          new_constants.collect do |suffix|
            mod_name == "Object" ? suffix : "#{mod_name}::#{suffix}"
          end
        end.flatten

        log "New constants: #{new_constants * ', '}"

        if aborting
          log "Error during loading, removing partially loaded constants "
          new_constants.each { |name| remove_constant name }
          new_constants.clear
        end
      end

      return new_constants
    ensure
      # Remove the stack frames that we added.
      if defined?(watch_frames) && ! watch_frames.blank?
        frame_ids = watch_frames.collect { |frame| frame.object_id }
        constant_watch_stack_mutex.synchronize do
          constant_watch_stack.delete_if do |watch_frame|
            frame_ids.include? watch_frame.object_id
          end
        end
      end
    end

    class LoadingModule #:nodoc:
      # Old style environment.rb referenced this method directly.  Please note, it doesn't
      # actually *do* anything any more.
      def self.root(*args)
        if defined?(Rails) && Rails.logger
          Rails.logger.warn "Your environment.rb uses the old syntax, it may not continue to work in future releases."
          Rails.logger.warn "For upgrade instructions please see: http://manuals.rubyonrails.com/read/book/19"
        end
      end
    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:
      name = case desc
        when String then desc.starts_with?('::') ? desc[2..-1] : desc
        when Symbol then desc.to_s
        when Module
          raise ArgumentError, "Anonymous modules have no name to be referenced by" if desc.name.blank?
          desc.name
        else raise TypeError, "Not a valid constant descriptor: #{desc.inspect}"
      end
    end

    def remove_constant(const) #:nodoc:
      return false unless qualified_const_defined? const

      const = $1 if /\A::(.*)\Z/ =~ const.to_s
      names = const.to_s.split('::')
      if names.size == 1 # It's under Object
        parent = Object
      else
        parent = (names[0..-2] * '::').constantize
      end

      log "removing constant #{const}"
      parent.instance_eval { remove_const names.last }
      return true
    end

    protected
      def log_call(*args)
        if logger && log_activity
          arg_str = args.collect { |arg| arg.inspect } * ', '
          /in `([a-z_\?\!]+)'/ =~ caller(1).first
          selector = $1 || '<unknown>'
          log "called #{selector}(#{arg_str})"
        end
      end

      def log(msg)
        if logger && log_activity
          logger.debug "Dependencies: #{msg}"
        end
      end
  end
end

ActiveSupport::Dependencies.hook!