aboutsummaryrefslogtreecommitdiffstats
path: root/activesupport/lib/active_support/evented_file_update_checker.rb
blob: 21fdf7bb807177e6c2da723e373d4a39a1742dca (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
require 'set'
require 'pathname'
require 'concurrent/atomic/atomic_boolean'

module ActiveSupport
  class EventedFileUpdateChecker #:nodoc: all
    def initialize(files, dirs = {}, &block)
      @ph    = PathHelper.new
      @files = files.map { |f| @ph.xpath(f) }.to_set

      @dirs = {}
      dirs.each do |dir, exts|
        @dirs[@ph.xpath(dir)] = Array(exts).map { |ext| @ph.normalize_extension(ext) }
      end

      @block   = block
      @updated = Concurrent::AtomicBoolean.new(false)
      @lcsp    = @ph.longest_common_subpath(@dirs.keys)

      if (dtw = directories_to_watch).any?
        # Loading listen triggers warnings. These are originated by a legit
        # usage of attr_* macros for private attributes, but adds a lot of noise
        # to our test suite. Thus, we lazy load it and disable warnings locally.
        silence_warnings do
          begin
            require 'listen'
          rescue LoadError => e
            raise LoadError, "Could not load the 'listen' gem. Add `gem 'listen'` to the development group of your Gemfile", e.backtrace
          end
        end
        Listen.to(*dtw, &method(:changed)).start
      end
    end

    def updated?
      @updated.true?
    end

    def execute
      @updated.make_false
      @block.call
    end

    def execute_if_updated
      if updated?
        yield if block_given?
        execute
        true
      end
    end

    private

      def changed(modified, added, removed)
        unless updated?
          @updated.make_true if (modified + added + removed).any? { |f| watching?(f) }
        end
      end

      def watching?(file)
        file = @ph.xpath(file)

        if @files.member?(file)
          true
        elsif file.directory?
          false
        else
          ext = @ph.normalize_extension(file.extname)

          file.dirname.ascend do |dir|
            if @dirs.fetch(dir, []).include?(ext)
              break true
            elsif dir == @lcsp || dir.root?
              break false
            end
          end
        end
      end

      def directories_to_watch
        dtw = (@files + @dirs.keys).map { |f| @ph.existing_parent(f) }
        dtw.compact!
        dtw.uniq!

        @ph.filter_out_descendants(dtw)
      end

    class PathHelper
      def xpath(path)
        Pathname.new(path).expand_path
      end

      def normalize_extension(ext)
        ext.to_s.sub(/\A\./, '')
      end

      # Given a collection of Pathname objects returns the longest subpath
      # common to all of them, or +nil+ if there is none.
      def longest_common_subpath(paths)
        return if paths.empty?

        lcsp = Pathname.new(paths[0])

        paths[1..-1].each do |path|
          until ascendant_of?(lcsp, path)
            if lcsp.root?
              # If we get here a root directory is not an ascendant of path.
              # This may happen if there are paths in different drives on
              # Windows.
              return
            else
              lcsp = lcsp.parent
            end
          end
        end

        lcsp
      end

      # Returns the deepest existing ascendant, which could be the argument itself.
      def existing_parent(dir)
        dir.ascend do |ascendant|
          break ascendant if ascendant.directory?
        end
      end

      # Filters out directories which are descendants of others in the collection (stable).
      def filter_out_descendants(dirs)
        return dirs if dirs.length < 2

        dirs_sorted_by_nparts = dirs.sort_by { |dir| dir.each_filename.to_a.length }
        descendants = []

        until dirs_sorted_by_nparts.empty?
          dir = dirs_sorted_by_nparts.shift

          dirs_sorted_by_nparts.reject! do |possible_descendant|
            ascendant_of?(dir, possible_descendant) && descendants << possible_descendant
          end
        end

        # Array#- preserves order.
        dirs - descendants
      end

      private

        def ascendant_of?(base, other)
          base != other && other.ascend do |ascendant|
            break true if base == ascendant
          end
        end
    end
  end
end