summaryrefslogtreecommitdiff
path: root/scss/compiler.py
blob: 96d54ecfa9a5c1290511eac9a3aaf09483101b1a (plain)
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
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals
from __future__ import division

from collections import defaultdict
from enum import Enum
import logging
from pathlib import Path
import re
import sys
import warnings

try:
    from collections import OrderedDict
except ImportError:
    # Backport
    from ordereddict import OrderedDict

import six

from scss.calculator import Calculator
from scss.cssdefs import _spaces_re
from scss.cssdefs import _escape_chars_re
from scss.cssdefs import _prop_split_re
from scss.errors import SassError
from scss.errors import SassBaseError
from scss.errors import SassImportError
from scss.extension import Extension
from scss.extension.core import CoreExtension
from scss.extension import NamespaceAdapterExtension
from scss.grammar import locate_blocks
from scss.rule import BlockAtRuleHeader
from scss.rule import Namespace
from scss.rule import RuleAncestry
from scss.rule import SassRule
from scss.rule import UnparsedBlock
from scss.selector import Selector
from scss.source import SourceFile
from scss.types import Arglist
from scss.types import List
from scss.types import Null
from scss.types import Number
from scss.types import String
from scss.types import Undefined
from scss.types import Url
from scss.util import normalize_var  # TODO put in...  namespace maybe?


# TODO should mention logging for the programmatic interface in the
# documentation
# TODO or have a little helper (or compiler setting) to turn it on
log = logging.getLogger(__name__)


_xcss_extends_re = re.compile(r'\s+extends\s+')


class OutputStyle(Enum):
    nested = ()
    compact = ()
    compressed = ()
    expanded = ()

    legacy = ()  # ???


class SassDeprecationWarning(UserWarning):
    # Note: DO NOT inherit from DeprecationWarning; it's turned off by default
    # in 2.7 and later!
    pass


def warn_deprecated(rule, message):
    warnings.warn(
        "{0} (at {1})".format(message, rule.file_and_line),
        SassDeprecationWarning,
        stacklevel=2,
    )


class Compiler(object):
    """A Sass compiler.  Stores settings and knows how to fire off a
    compilation.  Main entry point into compiling Sass.
    """
    def __init__(
            self, root=Path(), search_path=(),
            namespace=None, extensions=(CoreExtension,),
            output_style='nested', generate_source_map=False,
            live_errors=False, warn_unused_imports=False,
            ignore_parse_errors=False,
            loops_have_own_scopes=True,
            undefined_variables_fatal=True,
            super_selector='',
            ):
        """Configure a compiler.

        :param root: Directory to treat as the "project root".  Search paths
            and some custom extensions (e.g. Compass) are relative to this
            directory.  Defaults to the current directory.
        :type root: :class:`pathlib.Path`
        :param search_path: List of paths to search for ``@import``s, relative
            to ``root``.  Absolute and parent paths are allowed here, but
            ``@import`` will refuse to load files that aren't in one of the
            directories here.  Defaults to only the root.
        :type search_path: list of strings, :class:`pathlib.Path` objects, or
            something that implements a similar interface (useful for custom
            pseudo filesystems)
        """
        # TODO perhaps polite to automatically cast any string paths to Path?
        # but have to be careful since the api explicitly allows dummy objects.
        if root is None:
            self.root = None
        else:
            self.root = root.resolve()

        self.search_path = tuple(
            self.normalize_path(path)
            for path in search_path
        )

        self.extensions = []
        if namespace is not None:
            self.extensions.append(NamespaceAdapterExtension(namespace))
        for extension in extensions:
            if isinstance(extension, Extension):
                self.extensions.append(extension)
            elif (isinstance(extension, type) and
                    issubclass(extension, Extension)):
                self.extensions.append(extension())
            elif isinstance(extension, Namespace):
                self.extensions.append(
                    NamespaceAdapterExtension(extension))
            else:
                raise TypeError(
                    "Expected an Extension or Namespace, got: {0!r}"
                    .format(extension)
                )

        self.output_style = output_style
        self.generate_source_map = generate_source_map
        self.live_errors = live_errors
        self.warn_unused_imports = warn_unused_imports
        self.ignore_parse_errors = ignore_parse_errors
        self.loops_have_own_scopes = loops_have_own_scopes
        self.undefined_variables_fatal = undefined_variables_fatal
        self.super_selector = super_selector

    def normalize_path(self, path):
        if isinstance(path, six.string_types):
            path = Path(path)
        if path.is_absolute():
            return path
        if self.root is None:
            raise IOError("Can't make absolute path when root is None")
        return self.root / path

    def make_compilation(self):
        return Compilation(self)

    def call_and_catch_errors(self, f, *args, **kwargs):
        """Call the given function with the given arguments.  If it succeeds,
        return its return value.  If it raises a :class:`scss.errors.SassError`
        and `live_errors` is turned on, return CSS containing a traceback and
        error message.
        """
        try:
            return f(*args, **kwargs)
        except SassError as e:
            if self.live_errors:
                # TODO should this setting also capture and display warnings?
                return e.to_css()
            else:
                raise

    def compile(self, *filenames):
        compilation = self.make_compilation()
        for filename in filenames:
            # TODO maybe SourceFile should not be exposed to the end user, and
            # instead Compilation should have methods for add_string etc. that
            # can call normalize_path.
            # TODO it's not possible to inject custom files into the
            # /compiler/ as persistent across compiles, nor to provide "fake"
            # imports.  do we want the former?  is the latter better suited to
            # an extension?
            source = SourceFile.from_filename(self.normalize_path(filename))
            compilation.add_source(source)
        return self.call_and_catch_errors(compilation.run)

    def compile_string(self, string):
        source = SourceFile.from_string(string)
        compilation = self.make_compilation()
        compilation.add_source(source)
        return self.call_and_catch_errors(compilation.run)


def compile_file(filename, compiler_class=Compiler, **kwargs):
    """Compile a single file (provided as a :class:`pathlib.Path`), and return
    a string of CSS.

    Keyword arguments are passed along to the underlying `Compiler`.

    Note that the search path is set to the file's containing directory by
    default, unless you explicitly pass a ``search_path`` kwarg.

    :param filename: Path to the file to compile.
    :type filename: str, bytes, or :class:`pathlib.Path`
    """
    filename = Path(filename)
    if 'search_path' not in kwargs:
        kwargs['search_path'] = [filename.parent.resolve()]

    compiler = compiler_class(**kwargs)
    return compiler.compile(filename)


def compile_string(string, compiler_class=Compiler, **kwargs):
    """Compile a single string, and return a string of CSS.

    Keyword arguments are passed along to the underlying `Compiler`.
    """
    compiler = compiler_class(**kwargs)
    return compiler.compile_string(string)


class Compilation(object):
    """A single run of a compiler."""
    def __init__(self, compiler):
        self.compiler = compiler
        self.ignore_parse_errors = compiler.ignore_parse_errors

        # TODO this needs a write barrier, so assignment can't overwrite what's
        # in the original namespaces
        # TODO or maybe the extensions themselves should take care of that, so
        # it IS possible to overwrite from within sass, but only per-instance?
        self.root_namespace = Namespace.derive_from(*(
            ext.namespace for ext in compiler.extensions
            if ext.namespace
        ))

        self.sources = []
        self.source_index = {}
        self.dependency_map = defaultdict(frozenset)
        self.rules = []

    def should_scope_loop_in_rule(self, rule):
        """Return True iff a looping construct (@each, @for, @while, @if)
        should get its own scope, as is standard Sass behavior.
        """
        return rule.legacy_compiler_options.get(
            'control_scoping', self.compiler.loops_have_own_scopes)

    def add_source(self, source):
        if source.key in self.source_index:
            return self.source_index[source.key]
        self.sources.append(source)
        self.source_index[source.key] = source
        return source

    def run(self):
        # this will compile and manage rule: child objects inside of a node
        self.parse_children()

        # this will manage @extends
        self.rules = self.apply_extends(self.rules)

        rules_by_file, css_files = self.parse_properties()

        all_rules = 0
        all_selectors = 0
        exceeded = ''
        final_cont = ''
        files = len(css_files)
        for source_file in css_files:
            rules = rules_by_file[source_file]
            fcont, total_rules, total_selectors = self.create_css(rules)
            all_rules += total_rules
            all_selectors += total_selectors
            # TODO i would love for the output of this function to be something
            # useful for producing stats, so this stuff can live on the Scss
            # class only
            if not exceeded and all_selectors > 4095:
                exceeded = " (IE exceeded!)"
                log.error("Maximum number of supported selectors in Internet Explorer (4095) exceeded!")
            if files > 1 and self.compiler.generate_source_map:
                final_cont += "/* %s %s generated from '%s' add up to a total of %s %s accumulated%s */\n" % (
                    total_selectors,
                    'selector' if total_selectors == 1 else 'selectors',
                    source_file.path,
                    all_selectors,
                    'selector' if all_selectors == 1 else 'selectors',
                    exceeded)
            final_cont += fcont

        return final_cont

    def parse_selectors(self, raw_selectors):
        """
        Parses out the old xCSS "foo extends bar" syntax.

        Returns a 2-tuple: a set of selectors, and a set of extended selectors.
        """
        # Fix tabs and spaces in selectors
        raw_selectors = _spaces_re.sub(' ', raw_selectors)

        parts = _xcss_extends_re.split(raw_selectors, 1)  # handle old xCSS extends
        if len(parts) > 1:
            unparsed_selectors, unsplit_parents = parts
            # Multiple `extends` are delimited by `&`
            unparsed_parents = unsplit_parents.split('&')
        else:
            unparsed_selectors, = parts
            unparsed_parents = ()

        selectors = Selector.parse_many(unparsed_selectors)
        parents = [Selector.parse_one(parent) for parent in unparsed_parents]

        return selectors, parents

    # @print_timing(3)
    def parse_children(self, scope=None):
        children = []
        root_namespace = self.root_namespace
        for source_file in self.sources:
            rule = SassRule(
                source_file=source_file,

                unparsed_contents=source_file.contents,
                namespace=root_namespace,
            )
            self.rules.append(rule)
            children.append(rule)

        for rule in children:
            self.manage_children(rule, scope)

        self._warn_unused_imports(self.rules[0])

    def _warn_unused_imports(self, rule):
        if not rule.legacy_compiler_options.get(
                'warn_unused', self.compiler.warn_unused_imports):
            return

        for name, file_and_line in rule.namespace.unused_imports():
            log.warn("Unused @import: '%s' (%s)", name, file_and_line)

    def _make_calculator(self, namespace):
        return Calculator(
            namespace,
            ignore_parse_errors=self.ignore_parse_errors,
            undefined_variables_fatal=self.compiler.undefined_variables_fatal,
        )

    # @print_timing(4)
    def manage_children(self, rule, scope):
        try:
            self._manage_children_impl(rule, scope)
        except SassBaseError as e:
            e.add_rule(rule)
            raise
        except Exception as e:
            raise SassError(e, rule=rule)

    def _manage_children_impl(self, rule, scope):
        calculator = self._make_calculator(rule.namespace)

        for c_lineno, c_property, c_codestr in locate_blocks(rule.unparsed_contents):
            block = UnparsedBlock(rule, c_lineno, c_property, c_codestr)

            ####################################################################
            # At (@) blocks
            if block.is_atrule:
                # TODO particularly wild idea: allow extensions to handle
                # unrecognized blocks, and get the pyscss stuff out of the
                # core?  even move the core stuff into the core extension?
                code = block.directive
                code = '_at_' + code.lower().replace(' ', '_')[1:]
                try:
                    method = getattr(self, code)
                except AttributeError:
                    if block.unparsed_contents is None:
                        rule.properties.append((block.prop, None))
                    elif scope is None:  # needs to have no scope to crawl down the nested rules
                        self._nest_at_rules(rule, scope, block)
                else:
                    method(calculator, rule, scope, block)

            ####################################################################
            # Properties
            elif block.unparsed_contents is None:
                self._get_properties(rule, scope, block)

            # Nested properties
            elif block.is_scope:
                if block.header.unscoped_value:
                    # Possibly deal with default unscoped value
                    self._get_properties(rule, scope, block)

                rule.unparsed_contents = block.unparsed_contents
                subscope = (scope or '') + block.header.scope + '-'
                self.manage_children(rule, subscope)

            ####################################################################
            # Nested rules
            elif scope is None:  # needs to have no scope to crawl down the nested rules
                self._nest_rules(rule, scope, block)

    def _at_warn(self, calculator, rule, scope, block):
        """
        Implements @warn
        """
        value = calculator.calculate(block.argument)
        log.warn(repr(value))

    def _at_print(self, calculator, rule, scope, block):
        """
        Implements @print
        """
        value = calculator.calculate(block.argument)
        sys.stderr.write("%s\n" % value)

    def _at_raw(self, calculator, rule, scope, block):
        """
        Implements @raw
        """
        value = calculator.calculate(block.argument)
        sys.stderr.write("%s\n" % repr(value))

    def _at_dump_context(self, calculator, rule, scope, block):
        """
        Implements @dump_context
        """
        sys.stderr.write("%s\n" % repr(rule.namespace._variables))

    def _at_dump_functions(self, calculator, rule, scope, block):
        """
        Implements @dump_functions
        """
        sys.stderr.write("%s\n" % repr(rule.namespace._functions))

    def _at_dump_mixins(self, calculator, rule, scope, block):
        """
        Implements @dump_mixins
        """
        sys.stderr.write("%s\n" % repr(rule.namespace._mixins))

    def _at_dump_imports(self, calculator, rule, scope, block):
        """
        Implements @dump_imports
        """
        sys.stderr.write("%s\n" % repr(rule.namespace._imports))

    def _at_dump_options(self, calculator, rule, scope, block):
        """
        Implements @dump_options
        """
        sys.stderr.write("%s\n" % repr(rule.options))

    def _at_debug(self, calculator, rule, scope, block):
        """
        Implements @debug
        """
        setting = block.argument.strip()
        if setting.lower() in ('1', 'true', 't', 'yes', 'y', 'on'):
            setting = True
        elif setting.lower() in ('0', 'false', 'f', 'no', 'n', 'off', 'undefined'):
            setting = False
        self.ignore_parse_errors = setting
        log.info("Debug mode is %s", 'On' if self.ignore_parse_errors else 'Off')

    def _at_pdb(self, calculator, rule, scope, block):
        """
        Implements @pdb
        """
        try:
            import ipdb as pdb
        except ImportError:
            import pdb
        pdb.set_trace()

    def _at_extend(self, calculator, rule, scope, block):
        """
        Implements @extend
        """
        from scss.selector import Selector
        selectors = calculator.apply_vars(block.argument)
        rule.extends_selectors.extend(Selector.parse_many(selectors))

    def _at_return(self, calculator, rule, scope, block):
        """
        Implements @return
        """
        # TODO should assert this only happens within a @function
        ret = calculator.calculate(block.argument)
        raise SassReturn(ret)

    # @print_timing(10)
    def _at_option(self, calculator, rule, scope, block):
        """
        Implements @option
        """
        # TODO This only actually supports "style" (which only really makes
        # sense as the first thing in a single input file) or "warn_unused"
        # (which only makes sense at file level /at best/).  Explore either
        # replacing this with a better mechanism or dropping it entirely.
        # Note also that all rules share the same underlying legacy option
        # dict, so the rules aren't even lexically scoped like you might think,
        # and @importing a file can change the compiler!  That seems totally
        # wrong.
        for option in block.argument.split(','):
            key, colon, value = option.partition(':')
            key = key.strip().lower().replace('-', '_')
            value = value.strip().lower()

            if value in ('1', 'true', 't', 'yes', 'y', 'on'):
                value = True
            elif value in ('0', 'false', 'f', 'no', 'n', 'off', 'undefined'):
                value = False
            elif not colon:
                value = True

            if key == 'compress':
                warn_deprecated(
                    rule,
                    "The 'compress' @option is deprecated.  "
                    "Please use 'style' instead."
                )
                key = 'style'
                value = 'compressed' if value else 'legacy'

            if key in ('short_colors', 'reverse_colors'):
                warn_deprecated(
                    rule,
                    "The '{0}' @option no longer has any effect."
                    .format(key),
                )
                return
            elif key == 'style':
                try:
                    OutputStyle[value]
                except KeyError:
                    raise SassError("No such output style: {0}".format(value))
            elif key in ('warn_unused', 'control_scoping'):
                # TODO deprecate control_scoping?  or add it to compiler?
                if not isinstance(value, bool):
                    raise SassError("The '{0}' @option requires a bool, not {1!r}".format(key, value))
            else:
                raise SassError("Unknown @option: {0}".format(key))

            rule.legacy_compiler_options[key] = value

    def _get_funct_def(self, rule, calculator, argument):
        funct, lpar, argstr = argument.partition('(')
        funct = calculator.do_glob_math(funct)
        funct = normalize_var(funct.strip())
        argstr = argstr.strip()

        # Parse arguments with the argspec rule
        if lpar:
            if not argstr.endswith(')'):
                raise SyntaxError("Expected ')', found end of line for %s (%s)" % (funct, rule.file_and_line))
            argstr = argstr[:-1].strip()
        else:
            # Whoops, no parens at all.  That's like calling with no arguments.
            argstr = ''

        argspec_node = calculator.parse_expression(argstr, target='goal_argspec')
        return funct, argspec_node

    def _populate_namespace_from_call(self, name, callee_namespace, mixin, args, kwargs):
        # Mutation protection
        args = list(args)
        kwargs = OrderedDict(kwargs)

        #m_params = mixin[0]
        #m_defaults = mixin[1]
        #m_codestr = mixin[2]
        pristine_callee_namespace = mixin[3]
        callee_argspec = mixin[4]
        import_key = mixin[5]

        callee_calculator = self._make_calculator(callee_namespace)

        # Populate the mixin/function's namespace with its arguments
        for var_name, node in callee_argspec.iter_def_argspec():
            if args:
                # If there are positional arguments left, use the first
                value = args.pop(0)
            elif var_name in kwargs:
                # Try keyword arguments
                value = kwargs.pop(var_name)
            elif node is not None:
                # OK, try the default argument.  Using callee_calculator means
                # that default values of arguments can refer to earlier
                # arguments' values; yes, that is how Sass works.
                value = node.evaluate(callee_calculator, divide=True)
            else:
                # TODO this should raise
                value = Undefined()

            callee_namespace.set_variable(var_name, value, local_only=True)

        if callee_argspec.slurp:
            # Slurpy var gets whatever is left
            # TODO should preserve the order of extra kwargs
            sass_kwargs = []
            for key, value in kwargs.items():
                sass_kwargs.append((String(key[1:]), value))
            callee_namespace.set_variable(
                callee_argspec.slurp.name,
                Arglist(args, sass_kwargs))
            args = []
            kwargs = {}
        elif callee_argspec.inject:
            # Callee namespace gets all the extra kwargs whether declared or
            # not
            for var_name, value in kwargs.items():
                callee_namespace.set_variable(var_name, value, local_only=True)
            kwargs = {}

        # TODO would be nice to say where the mixin/function came from
        if kwargs:
            raise NameError("%s has no such argument %s" % (name, kwargs.keys()[0]))

        if args:
            raise NameError("%s received extra arguments: %r" % (name, args))

        pristine_callee_namespace.use_import(import_key)
        return callee_namespace

    # @print_timing(10)
    def _at_function(self, calculator, rule, scope, block):
        """
        Implements @mixin and @function
        """
        if not block.argument:
            raise SyntaxError("%s requires a function name (%s)" % (block.directive, rule.file_and_line))

        funct, argspec_node = self._get_funct_def(rule, calculator, block.argument)

        defaults = {}
        new_params = []

        for var_name, default in argspec_node.iter_def_argspec():
            new_params.append(var_name)
            if default is not None:
                defaults[var_name] = default

        # TODO a function or mixin is re-parsed every time it's called; there's
        # no AST for anything but expressions  :(
        mixin = [rule.source_file, block.lineno, block.unparsed_contents, rule.namespace, argspec_node, rule.source_file]
        if block.directive == '@function':
            def _call(mixin):
                def __call(namespace, *args, **kwargs):
                    source_file = mixin[0]
                    lineno = mixin[1]
                    m_codestr = mixin[2]
                    pristine_callee_namespace = mixin[3]
                    callee_namespace = pristine_callee_namespace.derive()

                    # TODO CallOp converts Sass names to Python names, so we
                    # have to convert them back to Sass names.  would be nice
                    # to avoid this back-and-forth somehow
                    kwargs = OrderedDict(
                        (normalize_var('$' + key), value)
                        for (key, value) in kwargs.items())

                    self._populate_namespace_from_call(
                        "Function {0}".format(funct),
                        callee_namespace, mixin, args, kwargs)

                    _rule = SassRule(
                        source_file=source_file,
                        lineno=lineno,
                        unparsed_contents=m_codestr,
                        namespace=callee_namespace,

                        # rule
                        import_key=rule.import_key,
                        legacy_compiler_options=rule.legacy_compiler_options,
                        options=rule.options,
                        properties=rule.properties,
                        extends_selectors=rule.extends_selectors,
                        ancestry=rule.ancestry,
                        nested=rule.nested,
                    )
                    # TODO supposed to throw an error if there's a slurpy arg
                    # but keywords() is never called on it
                    try:
                        self.manage_children(_rule, scope)
                    except SassReturn as e:
                        return e.retval
                    else:
                        return Null()
                return __call
            _mixin = _call(mixin)
            _mixin.mixin = mixin
            mixin = _mixin

        if block.directive == '@mixin':
            add = rule.namespace.set_mixin
        elif block.directive == '@function':
            add = rule.namespace.set_function

        # Register the mixin for every possible arity it takes
        if argspec_node.slurp or argspec_node.inject:
            add(funct, None, mixin)
        else:
            while len(new_params):
                add(funct, len(new_params), mixin)
                param = new_params.pop()
                if param not in defaults:
                    break
            if not new_params:
                add(funct, 0, mixin)
    _at_mixin = _at_function

    # @print_timing(10)
    def _at_include(self, calculator, rule, scope, block):
        """
        Implements @include, for @mixins
        """
        caller_namespace = rule.namespace
        caller_calculator = self._make_calculator(caller_namespace)
        funct, caller_argspec = self._get_funct_def(rule, caller_calculator, block.argument)

        # Render the passed arguments, using the caller's namespace
        args, kwargs = caller_argspec.evaluate_call_args(caller_calculator)

        argc = len(args) + len(kwargs)
        try:
            mixin = caller_namespace.mixin(funct, argc)
        except KeyError:
            try:
                # TODO maybe? don't do this, once '...' works
                # Fallback to single parameter:
                mixin = caller_namespace.mixin(funct, 1)
            except KeyError:
                log.error("Mixin not found: %s:%d (%s)", funct, argc, rule.file_and_line, extra={'stack': True})
                return
            else:
                args = [List(args, use_comma=True)]
                # TODO what happens to kwargs?

        source_file = mixin[0]
        lineno = mixin[1]
        m_codestr = mixin[2]
        pristine_callee_namespace = mixin[3]
        callee_argspec = mixin[4]
        if caller_argspec.inject and callee_argspec.inject:
            # DEVIATION: Pass the ENTIRE local namespace to the mixin (yikes)
            callee_namespace = Namespace.derive_from(
                caller_namespace,
                pristine_callee_namespace)
        else:
            callee_namespace = pristine_callee_namespace.derive()

        self._populate_namespace_from_call(
            "Mixin {0}".format(funct),
            callee_namespace, mixin, args, kwargs)

        _rule = SassRule(
            # These must be file and line in which the @include occurs
            source_file=rule.source_file,
            lineno=rule.lineno,

            # These must be file and line in which the @mixin was defined
            from_source_file=source_file,
            from_lineno=lineno,

            unparsed_contents=m_codestr,
            namespace=callee_namespace,

            # rule
            import_key=rule.import_key,
            legacy_compiler_options=rule.legacy_compiler_options,
            options=rule.options,
            properties=rule.properties,
            extends_selectors=rule.extends_selectors,
            ancestry=rule.ancestry,
            nested=rule.nested,
        )

        _rule.options['@content'] = block.unparsed_contents
        self.manage_children(_rule, scope)

    # @print_timing(10)
    def _at_content(self, calculator, rule, scope, block):
        """
        Implements @content
        """
        if '@content' not in rule.options:
            log.error("Content string not found for @content (%s)", rule.file_and_line)
        rule.unparsed_contents = rule.options.pop('@content', '')
        self.manage_children(rule, scope)

    # @print_timing(10)
    def _at_import(self, calculator, rule, scope, block):
        """
        Implements @import
        Load and import mixins and functions and rules
        """
        # TODO it would be neat to opt into warning that you're using
        # values/functions from a file you didn't explicitly import
        # TODO base-level directives, like @mixin or @charset, aren't allowed
        # to be @imported into a nested block
        # TODO i'm not sure we disallow them nested in the first place
        # TODO @import is disallowed within mixins, control directives
        # TODO @import doesn't take a block -- that's probably an issue with a
        # lot of our directives

        # TODO if there's any #{}-interpolation in the AST, this should become
        # a CSS import (though in practice Ruby only even evaluates it in url()
        # -- in a string it's literal!)

        sass_paths = calculator.evaluate_expression(block.argument)
        css_imports = []

        for sass_path in sass_paths:
            # These are the rules for when an @import is interpreted as a CSS
            # import:
            if (
                    # If it's a url()
                    isinstance(sass_path, Url) or
                    # If it's not a string (including `"foo" screen`, a List)
                    not isinstance(sass_path, String) or
                    # If the filename begins with an http protocol
                    sass_path.value.startswith(('http://', 'https://')) or
                    # If the filename ends with .css
                    sass_path.value.endswith('.css')):
                css_imports.append(sass_path.render(compress=False))
                continue

            # Should be left with a plain String
            name = sass_path.value

            source = None
            for extension in self.compiler.extensions:
                source = extension.handle_import(name, self, rule)
                if source:
                    break
            else:
                # Didn't find anything!
                raise SassImportError(name, self.compiler, rule=rule)

            source = self.add_source(source)

            if rule.namespace.has_import(source):
                # If already imported in this scope, skip
                # TODO this might not be right -- consider if you @import a
                # file at top level, then @import it inside a selector block!
                continue

            _rule = SassRule(
                source_file=source,
                lineno=block.lineno,
                unparsed_contents=source.contents,

                # rule
                legacy_compiler_options=rule.legacy_compiler_options,
                options=rule.options,
                properties=rule.properties,
                extends_selectors=rule.extends_selectors,
                ancestry=rule.ancestry,
                namespace=rule.namespace,
            )
            rule.namespace.add_import(source, rule)
            self.manage_children(_rule, scope)

        # Create a new @import rule for each import determined to be CSS
        for import_ in css_imports:
            # TODO this seems extremely janky (surely we should create an
            # actual new Rule), but the CSS rendering doesn't understand how to
            # print rules without blocks
            # TODO if this ever creates a new Rule, shuffle stuff around so
            # this is still hoisted to the top
            rule.properties.append(('@import ' + import_, None))

    # @print_timing(10)
    def _at_if(self, calculator, rule, scope, block):
        """
        Implements @if and @else if
        """
        # "@if" indicates whether any kind of `if` since the last `@else` has
        # succeeded, in which case `@else if` should be skipped
        if block.directive != '@if':
            if '@if' not in rule.options:
                raise SyntaxError("@else with no @if (%s)" % (rule.file_and_line,))
            if rule.options['@if']:
                # Last @if succeeded; stop here
                return

        condition = calculator.calculate(block.argument)
        if condition:
            inner_rule = rule.copy()
            inner_rule.unparsed_contents = block.unparsed_contents
            if not self.should_scope_loop_in_rule(inner_rule):
                # DEVIATION: Allow not creating a new namespace
                inner_rule.namespace = rule.namespace
            self.manage_children(inner_rule, scope)
        rule.options['@if'] = condition
    _at_else_if = _at_if

    # @print_timing(10)
    def _at_else(self, calculator, rule, scope, block):
        """
        Implements @else
        """
        if '@if' not in rule.options:
            log.error("@else with no @if (%s)", rule.file_and_line)
        val = rule.options.pop('@if', True)
        if not val:
            inner_rule = rule.copy()
            inner_rule.unparsed_contents = block.unparsed_contents
            inner_rule.namespace = rule.namespace  # DEVIATION: Commenting this line gives the Sass bahavior
            inner_rule.unparsed_contents = block.unparsed_contents
            self.manage_children(inner_rule, scope)

    # @print_timing(10)
    def _at_for(self, calculator, rule, scope, block):
        """
        Implements @for
        """
        var, _, name = block.argument.partition(' from ')
        frm, _, through = name.partition(' through ')
        if through:
            inclusive = True
        else:
            inclusive = False
            frm, _, through = frm.partition(' to ')
        frm = calculator.calculate(frm)
        through = calculator.calculate(through)
        try:
            frm = int(float(frm))
            through = int(float(through))
        except ValueError:
            return

        if frm > through:
            # DEVIATION: allow reversed '@for .. from .. through' (same as enumerate() and range())
            frm, through = through, frm
            rev = reversed
        else:
            rev = lambda x: x
        var = var.strip()
        var = calculator.do_glob_math(var)
        var = normalize_var(var)

        inner_rule = rule.copy()
        inner_rule.unparsed_contents = block.unparsed_contents
        if not self.should_scope_loop_in_rule(inner_rule):
            # DEVIATION: Allow not creating a new namespace
            inner_rule.namespace = rule.namespace

        if inclusive:
            through += 1
        for i in rev(range(frm, through)):
            inner_rule.namespace.set_variable(var, Number(i))
            self.manage_children(inner_rule, scope)

    # @print_timing(10)
    def _at_each(self, calculator, rule, scope, block):
        """
        Implements @each
        """
        varstring, _, valuestring = block.argument.partition(' in ')
        values = calculator.calculate(valuestring)
        if not values:
            return

        varlist = [
            normalize_var(calculator.do_glob_math(var.strip()))
            # TODO use list parsing here
            for var in varstring.split(",")
        ]

        # `@each $foo, in $bar` unpacks, but `@each $foo in $bar` does not!
        unpack = len(varlist) > 1
        if not varlist[-1]:
            varlist.pop()

        inner_rule = rule.copy()
        inner_rule.unparsed_contents = block.unparsed_contents
        if not self.should_scope_loop_in_rule(inner_rule):
            # DEVIATION: Allow not creating a new namespace
            inner_rule.namespace = rule.namespace

        for v in List.from_maybe(values):
            if unpack:
                v = List.from_maybe(v)
                for i, var in enumerate(varlist):
                    if i >= len(v):
                        value = Null()
                    else:
                        value = v[i]
                    inner_rule.namespace.set_variable(var, value)
            else:
                inner_rule.namespace.set_variable(varlist[0], v)
            self.manage_children(inner_rule, scope)

    # @print_timing(10)
    def _at_while(self, calculator, rule, scope, block):
        """
        Implements @while
        """
        first_condition = condition = calculator.calculate(block.argument)
        while condition:
            inner_rule = rule.copy()
            inner_rule.unparsed_contents = block.unparsed_contents
            if not self.should_scope_loop_in_rule(inner_rule):
                # DEVIATION: Allow not creating a new namespace
                inner_rule.namespace = rule.namespace
            self.manage_children(inner_rule, scope)
            condition = calculator.calculate(block.argument)
        rule.options['@if'] = first_condition

    # @print_timing(10)
    def _at_variables(self, calculator, rule, scope, block):
        """
        Implements @variables and @vars
        """
        warn_deprecated(
            rule,
            "@variables and @vars are deprecated.  "
            "Just assign variables at top-level.")
        _rule = rule.copy()
        _rule.unparsed_contents = block.unparsed_contents
        _rule.namespace = rule.namespace
        _rule.properties = {}
        self.manage_children(_rule, scope)
        for name, value in _rule.properties.items():
            rule.namespace.set_variable(name, value)
    _at_vars = _at_variables

    # @print_timing(10)
    def _get_properties(self, rule, scope, block):
        """
        Implements properties and variables extraction and assignment
        """
        prop, raw_value = (_prop_split_re.split(block.prop, 1) + [None])[:2]
        if raw_value is not None:
            raw_value = raw_value.strip()

        try:
            is_var = (block.prop[len(prop)] == '=')
        except IndexError:
            is_var = False
        if is_var:
            warn_deprecated(rule, "Assignment with = is deprecated; use :.")
        calculator = self._make_calculator(rule.namespace)
        prop = prop.strip()
        prop = calculator.do_glob_math(prop)
        if not prop:
            return

        _prop = (scope or '') + prop
        if is_var or prop.startswith('$') and raw_value is not None:
            # Pop off any flags: !default, !global
            is_default = False
            is_global = True  # eventually sass will default this to false
            while True:
                splits = raw_value.rsplit(None, 1)
                if len(splits) < 2 or not splits[1].startswith('!'):
                    break

                raw_value, flag = splits
                if flag == '!default':
                    is_default = True
                elif flag == '!global':
                    is_global = True
                else:
                    raise ValueError("Unrecognized flag: {0}".format(flag))

            # Variable assignment
            _prop = normalize_var(_prop)
            try:
                existing_value = rule.namespace.variable(_prop)
            except KeyError:
                existing_value = None

            is_defined = existing_value is not None and not existing_value.is_null
            if is_default and is_defined:
                pass
            else:
                if is_defined and prop.startswith('$') and prop[1].isupper():
                    log.warn("Constant %r redefined", prop)

                # Variable assignment is an expression, so it always performs
                # real division
                value = calculator.calculate(raw_value, divide=True)
                rule.namespace.set_variable(
                    _prop, value, local_only=not is_global)
        else:
            # Regular property destined for output
            _prop = calculator.apply_vars(_prop)
            if raw_value is None:
                value = None
            else:
                value = calculator.calculate(raw_value)

            if value is None:
                pass
            elif isinstance(value, six.string_types):
                # TODO kill this branch
                pass
            else:
                style = rule.legacy_compiler_options.get(
                    'style', self.compiler.output_style)
                compress = style == 'compressed'
                value = value.render(compress=compress)

            rule.properties.append((_prop, value))

    # @print_timing(10)
    def _nest_at_rules(self, rule, scope, block):
        """
        Implements @-blocks
        """
        # TODO handle @charset, probably?
        # Interpolate the current block
        # TODO this seems like it should be done in the block header.  and more
        # generally?
        calculator = self._make_calculator(rule.namespace)
        if block.header.argument:
            block.header.argument = calculator.apply_vars(block.header.argument)

        # TODO merge into RuleAncestry
        new_ancestry = list(rule.ancestry.headers)
        if block.directive == '@media' and new_ancestry:
            for i, header in reversed(list(enumerate(new_ancestry))):
                if header.is_selector:
                    continue
                elif header.directive == '@media':
                    new_ancestry[i] = BlockAtRuleHeader(
                        '@media',
                        "%s and %s" % (header.argument, block.argument))
                    break
                else:
                    new_ancestry.insert(i, block.header)
            else:
                new_ancestry.insert(0, block.header)
        else:
            new_ancestry.append(block.header)

        rule.descendants += 1
        new_rule = SassRule(
            source_file=rule.source_file,
            import_key=rule.import_key,
            lineno=block.lineno,
            unparsed_contents=block.unparsed_contents,

            legacy_compiler_options=rule.legacy_compiler_options,
            options=rule.options.copy(),
            #properties
            #extends_selectors
            ancestry=RuleAncestry(new_ancestry),

            namespace=rule.namespace.derive(),
            nested=rule.nested + 1,
        )
        self.rules.append(new_rule)
        rule.namespace.use_import(rule.source_file)
        self.manage_children(new_rule, scope)

        self._warn_unused_imports(new_rule)

    # @print_timing(10)
    def _nest_rules(self, rule, scope, block):
        """
        Implements Nested CSS rules
        """
        calculator = self._make_calculator(rule.namespace)
        raw_selectors = calculator.do_glob_math(block.prop)
        # DEVIATION: ruby sass doesn't support bare variables in selectors
        raw_selectors = calculator.apply_vars(raw_selectors)
        c_selectors, c_parents = self.parse_selectors(raw_selectors)
        if c_parents:
            warn_deprecated(
                rule,
                "The XCSS 'a extends b' syntax is deprecated.  "
                "Use 'a { @extend b; }' instead."
            )

        new_ancestry = rule.ancestry.with_nested_selectors(c_selectors)

        rule.descendants += 1
        new_rule = SassRule(
            source_file=rule.source_file,
            import_key=rule.import_key,
            lineno=block.lineno,
            unparsed_contents=block.unparsed_contents,

            legacy_compiler_options=rule.legacy_compiler_options,
            options=rule.options.copy(),
            #properties
            extends_selectors=c_parents,
            ancestry=new_ancestry,

            namespace=rule.namespace.derive(),
            nested=rule.nested + 1,
        )
        self.rules.append(new_rule)
        rule.namespace.use_import(rule.source_file)
        self.manage_children(new_rule, scope)

        self._warn_unused_imports(new_rule)

    # @print_timing(3)
    def apply_extends(self, rules):
        """Run through the given rules and translate all the pending @extends
        declarations into real selectors on parent rules.

        The list is modified in-place and also sorted in dependency order.
        """
        # Game plan: for each rule that has an @extend, add its selectors to
        # every rule that matches that @extend.
        # First, rig a way to find arbitrary selectors quickly.  Most selectors
        # revolve around elements, classes, and IDs, so parse those out and use
        # them as a rough key.  Ignore order and duplication for now.
        key_to_selectors = defaultdict(set)
        selector_to_rules = defaultdict(set)
        rule_selector_order = {}
        order = 0
        for rule in rules:
            for selector in rule.selectors:
                for key in selector.lookup_key():
                    key_to_selectors[key].add(selector)
                selector_to_rules[selector].add(rule)
                rule_selector_order[rule, selector] = order
                order += 1

        # Now go through all the rules with an @extends and find their parent
        # rules.
        for rule in rules:
            for selector in rule.extends_selectors:
                # This is a little dirty.  intersection isn't a class method.
                # Don't think about it too much.
                candidates = set.intersection(*(
                    key_to_selectors[key] for key in selector.lookup_key()))
                extendable_selectors = [
                    candidate for candidate in candidates
                    if candidate.is_superset_of(selector)]

                if not extendable_selectors:
                    # TODO implement !optional
                    warn_deprecated(
                        rule,
                        "Can't find any matching rules to extend {0!r} -- this"
                        "will be fatal in 2.0, unless !optional is specified!"
                        .format(selector.render()))
                    continue

                # Armed with a set of selectors that this rule can extend, do
                # some substitution and modify the appropriate parent rules.
                # One tricky bit: it's possible we're extending two selectors
                # that both exist in the same parent rule, in which case we
                # want to extend in the order the original selectors appear in
                # that rule.
                known_parents = []
                for extendable_selector in extendable_selectors:
                    parent_rules = selector_to_rules[extendable_selector]
                    for parent_rule in parent_rules:
                        if parent_rule is rule:
                            # Don't extend oneself
                            continue
                        known_parents.append(
                            (parent_rule, extendable_selector))
                # This will put our parents back in their original order
                known_parents.sort(key=rule_selector_order.__getitem__)

                for parent_rule, extendable_selector in known_parents:
                    more_parent_selectors = []

                    for rule_selector in rule.selectors:
                        more_parent_selectors.extend(
                            extendable_selector.substitute(
                                selector, rule_selector))

                    for parent in more_parent_selectors:
                        # Update indices, in case later rules try to extend
                        # this one
                        for key in parent.lookup_key():
                            key_to_selectors[key].add(parent)
                        selector_to_rules[parent].add(parent_rule)
                        rule_selector_order[parent_rule, parent] = order
                        order += 1

                    parent_rule.ancestry = (
                        parent_rule.ancestry.with_more_selectors(
                            more_parent_selectors))

        # Remove placeholder-only rules
        return [rule for rule in rules if not rule.is_pure_placeholder]

    # @print_timing(3)
    def parse_properties(self):
        css_files = []
        seen_files = set()
        rules_by_file = {}

        for rule in self.rules:
            source_file = rule.source_file
            rules_by_file.setdefault(source_file, []).append(rule)

            if rule.is_empty:
                continue

            if source_file not in seen_files:
                seen_files.add(source_file)
                css_files.append(source_file)

        return rules_by_file, css_files

    # @print_timing(3)
    def create_css(self, rules):
        """
        Generate the final CSS string
        """
        style = rules[0].legacy_compiler_options.get(
            'style', self.compiler.output_style)
        debug_info = self.compiler.generate_source_map

        if style == 'legacy':
            sc, sp, tb, nst, srnl, nl, rnl, lnl, dbg = True, ' ', '  ', False, '', '\n', '\n', '\n', debug_info
        elif style == 'compressed':
            sc, sp, tb, nst, srnl, nl, rnl, lnl, dbg = False, '', '', False, '', '', '', '', False
        elif style == 'compact':
            sc, sp, tb, nst, srnl, nl, rnl, lnl, dbg = True, ' ', '', False, '\n', ' ', '\n', ' ', debug_info
        elif style == 'expanded':
            sc, sp, tb, nst, srnl, nl, rnl, lnl, dbg = True, ' ', '  ', False, '\n', '\n', '\n', '\n', debug_info
        else:  # if style == 'nested':
            sc, sp, tb, nst, srnl, nl, rnl, lnl, dbg = True, ' ', '  ', True, '\n', '\n', '\n', ' ', debug_info

        return self._create_css(rules, sc, sp, tb, nst, srnl, nl, rnl, lnl, dbg)

    def _textwrap(self, txt, width=70):
        if not hasattr(self, '_textwrap_wordsep_re'):
            self._textwrap_wordsep_re = re.compile(r'(?<=,)\s+')
            self._textwrap_strings_re = re.compile(r'''(["'])(?:(?!\1)[^\\]|\\.)*\1''')

        # First, remove commas from anything within strings (marking commas as \0):
        def _repl(m):
            ori = m.group(0)
            fin = ori.replace(',', '\0')
            if ori != fin:
                subs[fin] = ori
            return fin
        subs = {}
        txt = self._textwrap_strings_re.sub(_repl, txt)

        # Mark split points for word separators using (marking spaces with \1):
        txt = self._textwrap_wordsep_re.sub('\1', txt)

        # Replace all the strings back:
        for fin, ori in subs.items():
            txt = txt.replace(fin, ori)

        # Split in chunks:
        chunks = txt.split('\1')

        # Break in lines of at most long_width width appending chunks:
        ln = ''
        lines = []
        long_width = int(width * 1.2)
        for chunk in chunks:
            _ln = ln + ' ' if ln else ''
            _ln += chunk
            if len(ln) >= width or len(_ln) >= long_width:
                if ln:
                    lines.append(ln)
                _ln = chunk
            ln = _ln
        if ln:
            lines.append(ln)

        return lines

    def _create_css(self, rules, sc=True, sp=' ', tb='  ', nst=True, srnl='\n', nl='\n', rnl='\n', lnl='', debug_info=False):
        super_selector = self.compiler.super_selector
        if super_selector:
            super_selector += ' '

        skip_selectors = False

        prev_ancestry_headers = []

        total_rules = 0
        total_selectors = 0

        result = ''
        dangling_property = False
        separate = False
        nesting = current_nesting = last_nesting = -1 if nst else 0
        nesting_stack = []
        for rule in rules:
            nested = rule.nested
            if nested <= 1:
                separate = True

            if nst:
                last_nesting = current_nesting
                current_nesting = nested

                delta_nesting = current_nesting - last_nesting
                if delta_nesting > 0:
                    nesting_stack += [nesting] * delta_nesting
                elif delta_nesting < 0:
                    nesting_stack = nesting_stack[:delta_nesting]
                    nesting = nesting_stack[-1]

            if rule.is_empty:
                continue

            if nst:
                nesting += 1

            ancestry = rule.ancestry
            ancestry_len = len(ancestry)

            first_mismatch = 0
            for i, (old_header, new_header) in enumerate(zip(prev_ancestry_headers, ancestry.headers)):
                if old_header != new_header:
                    first_mismatch = i
                    break

            # When sc is False, sets of properties are printed without a
            # trailing semicolon.  If the previous block isn't being closed,
            # that trailing semicolon needs adding in to separate the last
            # property from the next rule.
            if not sc and dangling_property and first_mismatch >= len(prev_ancestry_headers):
                result += ';'

            # Close blocks and outdent as necessary
            for i in range(len(prev_ancestry_headers), first_mismatch, -1):
                result += tb * (i - 1) + '}' + rnl

            # Open new blocks as necessary
            for i in range(first_mismatch, ancestry_len):
                header = ancestry.headers[i]

                if separate:
                    if result:
                        result += srnl
                    separate = False
                if debug_info:
                    def _print_debug_info(filename, lineno):
                        if debug_info == 'comments':
                            result = tb * (i + nesting) + "/* file: %s, line: %s */" % (filename, lineno) + nl
                        else:
                            filename = _escape_chars_re.sub(r'\\\1', filename)
                            result = tb * (i + nesting) + "@media -sass-debug-info{filename{font-family:file\:\/\/%s}line{font-family:\\00003%s}}" % (filename, lineno) + nl
                        return result

                    if rule.lineno and rule.source_file:
                        result += _print_debug_info(rule.source_file.path, rule.lineno)

                    if rule.from_lineno and rule.from_source_file:
                        result += _print_debug_info(rule.from_source_file.path, rule.from_lineno)

                if header.is_selector:
                    header_string = header.render(sep=',' + sp, super_selector=super_selector)
                    if nl:
                        header_string = (nl + tb * (i + nesting)).join(self._textwrap(header_string))
                else:
                    header_string = header.render()
                result += tb * (i + nesting) + header_string + sp + '{' + nl

                total_rules += 1
                if header.is_selector:
                    total_selectors += 1

            prev_ancestry_headers = ancestry.headers
            dangling_property = False

            if not skip_selectors:
                result += self._print_properties(rule.properties, sc, sp, tb * (ancestry_len + nesting), nl, lnl)
                dangling_property = True

        # Close all remaining blocks
        for i in reversed(range(len(prev_ancestry_headers))):
            result += tb * i + '}' + rnl

        # Always end with a newline, even in compressed mode
        if not result.endswith('\n'):
            result += '\n'

        return (result, total_rules, total_selectors)

    def _print_properties(self, properties, sc=True, sp=' ', tb='', nl='\n', lnl=' '):
        result = ''
        last_prop_index = len(properties) - 1
        for i, (name, value) in enumerate(properties):
            if value is None:
                prop = name
            elif value:
                if nl:
                    value = (nl + tb + tb).join(self._textwrap(value))
                prop = name + ':' + sp + value
            else:
                # Empty string means there's supposed to be a value but it
                # evaluated to nothing; skip this
                # TODO interacts poorly with last_prop_index
                continue

            if i == last_prop_index:
                if sc:
                    result += tb + prop + ';' + lnl
                else:
                    result += tb + prop + lnl
            else:
                result += tb + prop + ';' + nl
        return result


class SassReturn(SassBaseError):
    """Special control-flow exception used to hop up the stack from a Sass
    function's ``@return``.
    """
    def __init__(self, retval):
        super(SassReturn, self).__init__()
        self.retval = retval

    def __str__(self):
        return "Returning {0!r}".format(self.retval)