Class: PhraseAppUpdater::Differ

Inherits:
Object
  • Object
show all
Defined in:
lib/phraseapp_updater/differ.rb

Constant Summary collapse

SEPARATOR = 
'~~~'

Instance Method Summary collapse

Constructor Details

#initialize(verbose: false) ⇒ Differ

Returns a new instance of Differ.



12
13
14
 
# File 'lib/phraseapp_updater/differ.rb', line 12

def initialize(verbose: false)
  @verbose = verbose
end

Instance Method Details

#apply_diffs(hash, diffs) ⇒ Object 



65
66
67
 
# File 'lib/phraseapp_updater/differ.rb', line 65

def apply_diffs(hash, diffs)
  deep_compact!(Hashdiff.patch!(hash, diffs))
end

#resolve!(original:, primary:, secondary:) ⇒ Object 



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
 
# File 'lib/phraseapp_updater/differ.rb', line 69

def resolve!(original:, primary:, secondary:)
  # To appropriately cope with type changes on either sides, flatten the
  # trees before calculating the difference and then expand afterwards.
  f_original  = flatten(original)
  f_primary   = flatten(primary)
  f_secondary = flatten(secondary)

  primary_diffs   = Hashdiff.diff(f_original, f_primary)
  secondary_diffs = Hashdiff.diff(f_original, f_secondary)

  # However, flattening discards one critical piece of information: when we
  # have deleted or clobbered an entire prefix (subtree) from the original,
  # we want to consider this deletion atomic. If any of the changes is
  # cancelled, they must all be. Motivating example:
  #
  # original:  { word: { one: "..", "many": ".." } }
  # primary:   { word: { one: "..", "many": "..", "zero": ".." } }
  # secondary: { word: ".." }
  # would unexpectedly result in { word: { zero: ".." } }.
  #
  # Additionally calculate subtree prefixes that were deleted in `secondary`:
  secondary_deleted_prefixes =
    Hashdiff.diff(original, secondary, delimiter: SEPARATOR).lazy
      .select { |op, path, from, to| (op == "-" || op == "~") && from.is_a?(Hash) && !to.is_a?(Hash) }
      .map    { |op, path, from, to| path }
      .to_a


  resolved_diffs = resolve_diffs(primary:   primary_diffs,
                                 secondary: secondary_diffs,
                                 secondary_deleted_prefixes: secondary_deleted_prefixes)

  if @verbose
    STDERR.puts('Primary diffs:')
    primary_diffs.each { |d| STDERR.puts(d.inspect) }

    STDERR.puts('Secondary diffs:')
    secondary_diffs.each { |d| STDERR.puts(d.inspect) }

    STDERR.puts('Resolution:')
    resolved_diffs.each { |d| STDERR.puts(d.inspect) }
  end

  Hashdiff.patch!(f_original, resolved_diffs)

  expand(f_original)
end

#resolve_diffs(primary:, secondary:, secondary_deleted_prefixes:) ⇒ Object

Resolution strategy is that primary always wins in the event of a conflict



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
 
# File 'lib/phraseapp_updater/differ.rb', line 17

def resolve_diffs(primary:, secondary:, secondary_deleted_prefixes:)
  primary   = primary.index_by   { |op, path, from, to| path }
  secondary = secondary.index_by { |op, path, from, to| path }

  # As well as explicit conflicts, we want to make sure that deletions or
  # incompatible type changes to a `primary` key prevent addition of child
  # keys in `secondary`. Because input hashes are flattened, it's never
  # possible for a given path and its prefix to be in the same input.
  # For example, in:
  #
  # primary   = [["+", "a", 1]]
  # secondary = [["+", "a.b", 2]]
  #
  # the secondary change is impossible to perform on top of the primary, and
  # must be blocked.
  #
  # This applies in reverse: prefixes of paths in `p` need to be available
  # as hashes, so must not appear as terminals in `s`:
  #
  # primary   = [["+", "a.b", 2]]
  # secondary = [["+", "a",   1]]
  primary_prefixes = primary.keys.flat_map { |p| path_prefixes(p) }.to_set

  # Remove conflicting entries from secondary, recording incompatible
  # changes.
  path_conflicts = []
  secondary.delete_if do |path, diff|
    if primary_prefixes.include?(path) || primary.keys.any? { |pk| path.start_with?(pk) }
      path_conflicts << path unless primary.has_key?(path) && diff == primary[path]
      true
    else
      false
    end
  end

  # For all path conflicts matching secondary_deleted_prefixes, additionally
  # remove other changes with the same prefix.
  prefix_conflicts = secondary_deleted_prefixes.select do |prefix|
    path_conflicts.any? { |path| path.start_with?(prefix) }
  end

  secondary.delete_if do |path, diff|
    prefix_conflicts.any? { |prefix| path.start_with?(prefix) }
  end

  primary.values + secondary.values
end

#restore_deletions(current, previous) ⇒ Object

Prefer everything in current except deletions, which are restored from previous if available



120
121
122
 
# File 'lib/phraseapp_updater/differ.rb', line 120

def restore_deletions(current, previous)
  current.deep_merge(previous)
end