Module: Sprockets::SourceMapUtils

Extended by:
SourceMapUtils
Included in:
Base, SourceMapUtils
Defined in:
lib/sprockets/source_map_utils.rb

Constant Summary collapse

VLQ_BASE_SHIFT =

Public: Base64 VLQ encoding

Adopted from ConradIrwin/ruby-source_map

https://github.com/ConradIrwin/ruby-source_map/blob/master/lib/source_map/vlq.rb

Resources

http://en.wikipedia.org/wiki/Variable-length_quantity
https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit
https://github.com/mozilla/source-map/blob/master/lib/source-map/base64-vlq.js
5
VLQ_BASE =
1 << VLQ_BASE_SHIFT
VLQ_BASE_MASK =
VLQ_BASE - 1
VLQ_CONTINUATION_BIT =
VLQ_BASE
BASE64_DIGITS =
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split('')
BASE64_VALUES =
(0...64).inject({}) { |h, i| h[BASE64_DIGITS[i]] = i; h }

Instance Method Summary collapse

Instance Method Details

#bsearch_mappings(mappings, offset, from = 0, to = mappings.size - 1) ⇒ Object

Public: Search Array of mappings for closest offset.

mappings - Array of mapping Hash objects offset - Array [line, column]

Returns mapping Hash object.


273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
# File 'lib/sprockets/source_map_utils.rb', line 273

def bsearch_mappings(mappings, offset, from = 0, to = mappings.size - 1)
  mid = (from + to) / 2

  if from > to
    return from < 1 ? nil : mappings[from-1]
  end

  case compare_source_offsets(offset, mappings[mid][:generated])
  when 0
    mappings[mid]
  when -1
    bsearch_mappings(mappings, offset, from, mid - 1)
  when 1
    bsearch_mappings(mappings, offset, mid + 1, to)
  end
end

#combine_source_maps(first, second) ⇒ Object

Public: Combine two seperate source map transformations into a single mapping.

Source transformations may happen in discrete steps producing separate source maps. These steps can be combined into a single mapping back to the source.

For an example, CoffeeScript may transform a file producing a map. Then Uglifier processes the result and produces another map. The CoffeeScript map can be combined with the Uglifier map so the source lines of the minified output can be traced back to the original CoffeeScript file.

Returns a source map hash.


156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
# File 'lib/sprockets/source_map_utils.rb', line 156

def combine_source_maps(first, second)
  return second unless first

  _first  = decode_source_map(first)
  _second = decode_source_map(second)

  new_mappings = []

  _second[:mappings].each do |m|
    first_line = bsearch_mappings(_first[:mappings], m[:original])
    new_mappings << first_line.merge(generated: m[:generated]) if first_line
  end

  _first[:mappings] = new_mappings

  encode_source_map(_first)
end

#compare_source_offsets(a, b) ⇒ Object

Public: Compare two source map offsets.

Compatible with Array#sort.

a - Array [line, column] b - Array [line, column]

Returns -1 if a < b, 0 if a == b and 1 if a > b.


254
255
256
257
258
259
260
261
262
263
264
265
# File 'lib/sprockets/source_map_utils.rb', line 254

def compare_source_offsets(a, b)
  diff = a[0] - b[0]
  diff = a[1] - b[1] if diff == 0

  if diff < 0
    -1
  elsif diff > 0
    1
  else
    0
  end
end

#concat_source_maps(a, b) ⇒ Object

Public: Concatenate two source maps.

For an example, if two js scripts are concatenated, the individual source maps for those files can be concatenated to map back to the originals.

Examples

script3 = "#{script1}#{script2}"
map3    = concat_source_maps(map1, map2)

a - Source map hash b - Source map hash

Returns a new source map hash.


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
# File 'lib/sprockets/source_map_utils.rb', line 73

def concat_source_maps(a, b)
  return a || b unless a && b
  a = make_index_map(a)
  b = make_index_map(b)

  offset = 0
  if a["sections"].count != 0 && !a["sections"].last["map"]["mappings"].empty?
    last_line_count = a["sections"].last["map"].delete("x_sprockets_linecount")
    offset += last_line_count

    last_offset = a["sections"].last["offset"]["line"]
    offset += last_offset
  end

  a["sections"] += b["sections"].map do |section|
    {
      "offset" => section["offset"].merge({ "line" => section["offset"]["line"] + offset }),
      "map"    => section["map"].merge({
        "sources" => section["map"]["sources"].map do |source|
          PathUtils.relative_path_from(a["file"], PathUtils.join(File.dirname(b["file"]), source))
        end
      })
    }
  end
  a
end

#decode_source_map(map) ⇒ Object

Public: Decompress source map

Example:

decode_source_map(map)
# => {
  version:  3,
  file:     "..",
  mappings: [
    { source: "..", generated: [0, 0], original: [0, 0], name: ".."}, ..
  ],
  sources:  [..],
  names:    [..]
}

map - Source map hash (v3 spec)

Returns an uncompressed source map hash


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
# File 'lib/sprockets/source_map_utils.rb', line 192

def decode_source_map(map)
  return nil unless map

  mappings, sources, names = [], [], []
  if map["sections"]
    map["sections"].each do |s|
      mappings += decode_source_map(s["map"])[:mappings].each do |m|
        m[:generated][0] += s["offset"]["line"]
        m[:generated][1] += s["offset"]["column"]
      end
      sources |= s["map"]["sources"]
      names   |= s["map"]["names"]
    end
  else
    mappings = decode_vlq_mappings(map["mappings"], sources: map["sources"], names: map["names"])
    sources  = map["sources"]
    names    = map["names"]
  end
  {
    version:  3,
    file:     map["file"],
    mappings: mappings,
    sources:  sources,
    names:    names
  }
end

#decode_vlq_mappings(str, sources: [], names: []) ⇒ Object

Public: Decode VLQ mappings and match up sources and symbol names.

str - VLQ string from 'mappings' attribute sources - Array of Strings from 'sources' attribute names - Array of Strings from 'names' attribute

Returns an Array of Mappings.


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
# File 'lib/sprockets/source_map_utils.rb', line 297

def decode_vlq_mappings(str, sources: [], names: [])
  mappings = []

  source_id       = 0
  original_line   = 1
  original_column = 0
  name_id         = 0

  vlq_decode_mappings(str).each_with_index do |group, index|
    generated_column = 0
    generated_line   = index + 1

    group.each do |segment|
      generated_column += segment[0]
      generated = [generated_line, generated_column]

      if segment.size >= 4
        source_id        += segment[1]
        original_line    += segment[2]
        original_column  += segment[3]

        source   = sources[source_id]
        original = [original_line, original_column]
      else
        # TODO: Research this case
        next
      end

      if segment[4]
        name_id += segment[4]
        name     = names[name_id]
      end

      mapping = {source: source, generated: generated, original: original}
      mapping[:name] = name if name
      mappings << mapping
    end
  end

  mappings
end

#encode_source_map(map) ⇒ Object

Public: Compress source map

Example:

encode_source_map(map)
# => {
  "version"  => 3,
  "file"     => "..",
  "mappings" => "AAAA;AACA;..;AACA",
  "sources"  => [..],
  "names"    => [..]
}

map - Source map hash (uncompressed)

Returns a compressed source map hash according to source map spec v3


235
236
237
238
239
240
241
242
243
244
# File 'lib/sprockets/source_map_utils.rb', line 235

def encode_source_map(map)
  return nil unless map
  {
    "version"  => map[:version],
    "file"     => map[:file],
    "mappings" => encode_vlq_mappings(map[:mappings], sources: map[:sources], names: map[:names]),
    "sources"  => map[:sources],
    "names"    => map[:names]
  }
end

#encode_vlq_mappings(mappings, sources: nil, names: nil) ⇒ Object

Public: Encode mappings Hash into a VLQ encoded String.

mappings - Array of Hash mapping objects sources - Array of String sources (default: mappings source order) names - Array of String names (default: mappings name order)

Returns a VLQ encoded String.


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
# File 'lib/sprockets/source_map_utils.rb', line 346

def encode_vlq_mappings(mappings, sources: nil, names: nil)
  sources ||= mappings.map { |m| m[:source] }.uniq.compact
  names   ||= mappings.map { |m| m[:name] }.uniq.compact

  sources_index = Hash[sources.each_with_index.to_a]
  names_index   = Hash[names.each_with_index.to_a]

  source_id     = 0
  source_line   = 1
  source_column = 0
  name_id       = 0

   = mappings.group_by { |m| m[:generated][0] }

  ary = (1..(.keys.max || 1)).map do |line|
    generated_column = 0

    ([line] || []).map do |mapping|
      group = []
      group << mapping[:generated][1] - generated_column
      group << sources_index[mapping[:source]] - source_id
      group << mapping[:original][0] - source_line
      group << mapping[:original][1] - source_column
      group << names_index[mapping[:name]] - name_id if mapping[:name]

      generated_column = mapping[:generated][1]
      source_id        = sources_index[mapping[:source]]
      source_line      = mapping[:original][0]
      source_column    = mapping[:original][1]
      name_id          = names_index[mapping[:name]] if mapping[:name]

      group
    end
  end

  vlq_encode_mappings(ary)
end

#format_source_map(map, input) ⇒ Object

Public: Transpose source maps into a standard format

NOTE: Does not support index maps

version => 3 file => logical path sources => relative from filename

Unnecessary attributes are removed

Example

map#=> {
#  "version"        => 3,
#  "file"           => "stdin",
#  "sourceRoot"     => "",
#  "sourceContents" => "blah blah blah",
#  "sources"        => [/root/logical/path.js],
#  "names"          => [..],
#}

format_source_map(map, input)#=> {
#  "version"        => 3,
#  "file"           => "logical/path.js",
#  "sources"        => ["path.js"],
#  "names"          => [..],
#}


37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
# File 'lib/sprockets/source_map_utils.rb', line 37

def format_source_map(map, input)
  filename      = input[:filename]
  load_path     = input[:load_path]
  load_paths    = input[:environment].config[:paths]
  mime_exts     = input[:environment].config[:mime_exts]
  pipeline_exts = input[:environment].config[:pipeline_exts]
  file          = PathUtils.split_subpath(load_path, filename)
  {
    "version"  => 3,
    "file"     => file,
    "mappings" => map["mappings"],
    "sources"  => map["sources"].map do |source|
      source = URIUtils.split_file_uri(source)[2] if source.start_with? "file://"
      source = PathUtils.join(File.dirname(filename), source) unless PathUtils.absolute_path?(source)
      _, source = PathUtils.paths_split(load_paths, source)
      source = PathUtils.relative_path_from(file, source)
      PathUtils.set_pipeline(source, mime_exts, pipeline_exts, :source)
    end,
    "names"    => map["names"]
  }
end

#make_index_map(map) ⇒ Object

Public: Converts source map to index map

Example:

map
# => {
  "version"  => 3,
  "file"     => "..",
  "mappings" => "AAAA;AACA;..;AACA",
  "sources"  => [..],
  "names"    => [..]
}
make_index_map(map)
# => {
  "version"  => 3,
  "file"     => "..",
  "sections" => [
    {
      "offset" => { "line" => 0, "column" => 0 },
      "map"    => {
        "version"  => 3,
        "file"     => "..",
        "mappings" => "AAAA;AACA;..;AACA",
        "sources"  => [..],
        "names"    => [..]
      }
    }
  ]
}

129
130
131
132
133
134
135
136
137
138
139
140
141
# File 'lib/sprockets/source_map_utils.rb', line 129

def make_index_map(map)
  return map if map.key? "sections"
  {
    "version"  => map["version"],
    "file"     => map["file"],
    "sections" => [
      {
        "offset" => { "line" => 0, "column" => 0 },
        "map"    => map
      }
    ]
  }
end

#vlq_decode(str) ⇒ Object

Public: Decode a VLQ string.

str - VLQ encoded String

Returns an Array of Integers.


429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
# File 'lib/sprockets/source_map_utils.rb', line 429

def vlq_decode(str)
  result = []
  shift = 0
  value = 0
  i = 0

  while i < str.size do
    digit = BASE64_VALUES[str[i]]
    raise ArgumentError unless digit
    continuation = (digit & VLQ_CONTINUATION_BIT) != 0
    digit &= VLQ_CONTINUATION_BIT - 1
      value += digit << shift
    if continuation
      shift += VLQ_BASE_SHIFT
    else
      result << ((value & 1) == 1 ? -(value >> 1) : value >> 1)
      value = shift = 0
    end
    i += 1
  end
  result
end

#vlq_decode_mappings(str) ⇒ Object

Public: Decode a VLQ string into mapping numbers.

str - VLQ encoded String

Returns an two dimensional Array of Integers.


470
471
472
473
474
475
476
477
478
479
480
481
# File 'lib/sprockets/source_map_utils.rb', line 470

def vlq_decode_mappings(str)
  mappings = []

  str.split(';').each_with_index do |group, index|
    mappings[index] = []
    group.split(',').each do |segment|
      mappings[index] << vlq_decode(segment)
    end
  end

  mappings
end

#vlq_encode(ary) ⇒ Object

Public: Encode a list of numbers into a compact VLQ string.

ary - An Array of Integers

Returns a VLQ String.


408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
# File 'lib/sprockets/source_map_utils.rb', line 408

def vlq_encode(ary)
  result = []
  ary.each do |n|
    vlq = n < 0 ? ((-n) << 1) + 1 : n << 1
    loop do
      digit  = vlq & VLQ_BASE_MASK
      vlq  >>= VLQ_BASE_SHIFT
      digit |= VLQ_CONTINUATION_BIT if vlq > 0
      result << BASE64_DIGITS[digit]

      break unless vlq > 0
    end
  end
  result.join
end

#vlq_encode_mappings(ary) ⇒ Object

Public: Encode a mapping array into a compact VLQ string.

ary - Two dimensional Array of Integers.

Returns a VLQ encoded String seperated by , and ;.


457
458
459
460
461
462
463
# File 'lib/sprockets/source_map_utils.rb', line 457

def vlq_encode_mappings(ary)
  ary.map { |group|
    group.map { |segment|
      vlq_encode(segment)
    }.join(',')
  }.join(';')
end