ebnf.py 27.5 KB
Newer Older
1
"""ebnf.py - EBNF -> Python-Parser compilation for DHParser
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

Copyright 2016  by Eckhart Arnold (arnold@badw.de)
                Bavarian Academy of Sciences an Humanities (badw.de)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied.  See the License for the specific language governing
permissions and limitations under the License.
"""

from functools import partial
20
21
import keyword
import os
22
23
24
25
26
try:
    import regex as re
except ImportError:
    import re

27
from .toolkit import load_if_file, escape_re, md5, sane_parser_name
Eckhart Arnold's avatar
Eckhart Arnold committed
28
from .parsers import GrammarBase, mixin_comment, nil_scanner, Forward, RE, NegativeLookahead, \
29
30
    Alternative, Sequence, Optional, Required, OneOrMore, ZeroOrMore, Token, CompilerBase, \
    Capture, Retrieve
31
from .syntaxtree import Node, traverse, remove_enclosing_delimiters, reduce_single_child, \
di68kap's avatar
di68kap committed
32
    replace_by_single_child, TOKEN_KEYWORD, remove_expendables, remove_tokens, flatten, \
33
    forbid, assert_content, WHITESPACE_KEYWORD, key_parser_name, key_tag_name
Eckhart Arnold's avatar
Eckhart Arnold committed
34
from .versionnumber import __version__
35
36


37
38
39
40
41
__all__ = ['get_ebnf_scanner',
           'get_ebnf_grammar',
           'get_ebnf_transformer',
           'get_ebnf_compiler',
           'EBNFGrammar',
42
           'EBNFTransformer',
Eckhart Arnold's avatar
Eckhart Arnold committed
43
           'EBNFCompilerError',
44
45
           'EBNFCompiler',
           'grammar_changed']
46
47


Eckhart Arnold's avatar
Eckhart Arnold committed
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
########################################################################
#
# EBNF scanning
#
########################################################################


def get_ebnf_scanner():
    return nil_scanner


########################################################################
#
# EBNF parsing
#
########################################################################


66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
class EBNFGrammar(GrammarBase):
    r"""Parser for an EBNF source file, with this grammar:

    # EBNF-Grammar in EBNF

    @ comment    =  /#.*(?:\n|$)/                    # comments start with '#' and eat all chars up to and including '\n'
    @ whitespace =  /\s*/                            # whitespace includes linefeed
    @ literalws  =  right                            # trailing whitespace of literals will be ignored tacitly

    syntax     =  [~//] { definition | directive } §EOF
    definition =  symbol §"=" expression
    directive  =  "@" §symbol §"=" ( regexp | literal | list_ )

    expression =  term { "|" term }
    term       =  { factor }+
    factor     =  [flowmarker] [retrieveop] symbol !"="   # negative lookahead to be sure it's not a definition
                | [flowmarker] literal
                | [flowmarker] regexp
                | [flowmarker] group
85
                | [flowmarker] regexchain
86
87
88
89
90
91
92
93
94
                | [flowmarker] oneormore
                | repetition
                | option

    flowmarker =  "!"  | "&"  | "§" |                # '!' negative lookahead, '&' positive lookahead, '§' required
                  "-!" | "-&"                        # '-' negative lookbehind, '-&' positive lookbehind
    retrieveop =  "::" | ":"                         # '::' pop, ':' retrieve

    group      =  "(" expression §")"
95
    regexchain =  ">" expression §"<"                # compiles "expression" into a singular regular expression
96
97
    oneormore  =  "{" expression "}+"
    repetition =  "{" expression §"}"
98
99
    option     =  "[" expression §"]"

100
101
102
103
104
105
    symbol     =  /(?!\d)\w+/~                       # e.g. expression, factor, parameter_list
    literal    =  /"(?:[^"]|\\")*?"/~                # e.g. "(", '+', 'while'
                | /'(?:[^']|\\')*?'/~                # whitespace following literals will be ignored tacitly.
    regexp     =  /~?\/(?:[^\/]|(?<=\\)\/)*\/~?/~    # e.g. /\w+/, ~/#.*(?:\n|$)/~
                                                     # '~' is a whitespace-marker, if present leading or trailing
                                                     # whitespace of a regular expression will be ignored tacitly.
106
    list_      =  /\w+/~ { "," /\w+/~ }              # comma separated list of symbols, e.g. BEGIN_LIST, END_LIST,
107
108
109
110
                                                     # BEGIN_QUOTE, END_QUOTE ; see CommonMark/markdown.py for an exmaple
    EOF =  !/./
    """
    expression = Forward()
111
    source_hash__ = "a410e1727fb7575e98ff8451dbf8f3bd"
112
    parser_initialization__ = "upon instatiation"
113
114
    COMMENT__ = r'#.*(?:\n|$)'
    WSP__ = mixin_comment(whitespace=r'\s*', comment=r'#.*(?:\n|$)')
115
    wspL__ = ''
116
    wspR__ = WSP__
117
    EOF = NegativeLookahead(RE('.', wR=''))
118
    list_ = Sequence(RE('\\w+'), ZeroOrMore(Sequence(Token(","), RE('\\w+'))))
119
120
121
    regexp = RE('~?/(?:[^/]|(?<=\\\\)/)*/~?')
    literal = Alternative(RE('"(?:[^"]|\\\\")*?"'), RE("'(?:[^']|\\\\')*?'"))
    symbol = RE('(?!\\d)\\w+')
122
    option = Sequence(Token("["), expression, Required(Token("]")))
123
124
    repetition = Sequence(Token("{"), expression, Required(Token("}")))
    oneormore = Sequence(Token("{"), expression, Token("}+"))
125
    regexchain = Sequence(Token("<"), expression, Required(Token(">")))
126
127
128
129
130
    group = Sequence(Token("("), expression, Required(Token(")")))
    retrieveop = Alternative(Token("::"), Token(":"))
    flowmarker = Alternative(Token("!"), Token("&"), Token("§"), Token("-!"), Token("-&"))
    factor = Alternative(Sequence(Optional(flowmarker), Optional(retrieveop), symbol, NegativeLookahead(Token("="))),
                         Sequence(Optional(flowmarker), literal), Sequence(Optional(flowmarker), regexp),
131
132
                         Sequence(Optional(flowmarker), group), Sequence(Optional(flowmarker), regexchain),
                         Sequence(Optional(flowmarker), oneormore), repetition, option)
133
134
135
136
    term = OneOrMore(factor)
    expression.set(Sequence(term, ZeroOrMore(Sequence(Token("|"), term))))
    directive = Sequence(Token("@"), Required(symbol), Required(Token("=")), Alternative(regexp, literal, list_))
    definition = Sequence(symbol, Required(Token("=")), expression)
137
    syntax = Sequence(Optional(RE('', wR='', wL=WSP__)), ZeroOrMore(Alternative(definition, directive)), Required(EOF))
138
139
140
    root__ = syntax


Eckhart Arnold's avatar
Eckhart Arnold committed
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
def grammar_changed(grammar_class, grammar_source):
    """Returns ``True`` if ``grammar_class`` does not reflect the latest
    changes of ``grammar_source``

    Parameters:
        grammar_class:  the parser class representing the grammar
            or the file name of a compiler suite containing the grammar
        grammar_source:  File name or string representation of the
            EBNF code of the grammar

    Returns (bool):
        True, if the source text of the grammar is different from the
        source from which the grammar class was generated
    """
    grammar = load_if_file(grammar_source)
    chksum = md5(grammar, __version__)
    if isinstance(grammar_class, str):
        # grammar_class = load_compiler_suite(grammar_class)[1]
        with open(grammar_class, 'r', encoding='utf8') as f:
            pycode = f.read()
        m = re.search('class \w*\(GrammarBase\)', pycode)
        if m:
            m = re.search('    source_hash__ *= *"([a-z0-9]*)"',
                          pycode[m.span()[1]:])
            return not (m and m.groups() and m.groups()[-1] == chksum)
        else:
            return True
    else:
        return chksum != grammar_class.source_hash__


def get_ebnf_grammar():
    global thread_local_ebnf_grammar_singleton
    try:
        grammar = thread_local_ebnf_grammar_singleton
        return grammar
    except NameError:
        thread_local_ebnf_grammar_singleton = EBNFGrammar()
        return thread_local_ebnf_grammar_singleton


########################################################################
#
# EBNF concrete to abstract syntax tree transformation and validation
#
########################################################################


189
190
#TODO: Add Capture and Retrieve Validation: A variable mustn't be captured twice before retrival?!?

191
EBNF_transformation_table = {
192
193
194
195
196
    # AST Transformations for EBNF-grammar
    "syntax":
        remove_expendables,
    "directive, definition":
        partial(remove_tokens, tokens={'@', '='}),
Eckhart Arnold's avatar
Eckhart Arnold committed
197
    "expression":
198
        [replace_by_single_child, flatten,
Eckhart Arnold's avatar
Eckhart Arnold committed
199
         partial(remove_tokens, tokens={'|'})],
200
201
202
203
204
    "term":
        [replace_by_single_child, flatten],  # supports both idioms:  "{ factor }+" and "factor { factor }"
    "factor, flowmarker, retrieveop":
        replace_by_single_child,
    "group":
205
206
207
        [remove_enclosing_delimiters, replace_by_single_child],
    "oneormore, repetition, option, regexchain":
        [reduce_single_child, remove_enclosing_delimiters],
208
    "symbol, literal, regexp":
209
210
211
        [remove_expendables, reduce_single_child],
    (TOKEN_KEYWORD, WHITESPACE_KEYWORD):
        [remove_expendables, reduce_single_child],
212
    "list_":
213
        [flatten, partial(remove_tokens, tokens={','})],
214
215
216
217
    "":
        [remove_expendables, replace_by_single_child]
}

218

219
EBNF_validation_table = {
220
221
    # Semantic validation on the AST
    "repetition, option, oneormore":
222
        [partial(forbid, child_tags=['repetition', 'option', 'oneormore']),
223
224
         partial(assert_content, regex=r'(?!§)')],
}
225

226

227
def EBNFTransformer(syntax_tree):
228
229
    for processing_table, key_func in [(EBNF_transformation_table, key_parser_name),
                                       (EBNF_validation_table, key_tag_name)]:
230
        traverse(syntax_tree, processing_table, key_func)
di68kap's avatar
di68kap committed
231
232


Eckhart Arnold's avatar
Eckhart Arnold committed
233
def get_ebnf_transformer():
234
    return EBNFTransformer
Eckhart Arnold's avatar
Eckhart Arnold committed
235
236
237
238
239
240
241
242


########################################################################
#
# EBNF abstract syntax tree to Python parser compilation
#
########################################################################

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
SCANNER_FACTORY = '''
def get_{NAME}_scanner():
    return {NAME}Scanner
'''


GRAMMAR_FACTORY = '''
def get_{NAME}_grammar():
    global thread_local_{NAME}_grammar_singleton
    try:
        grammar = thread_local_{NAME}_grammar_singleton
        return grammar
    except NameError:
        thread_local_{NAME}_grammar_singleton = {NAME}Grammar()
        return thread_local_{NAME}_grammar_singleton
'''


TRANSFORMER_FACTORY = '''
def get_{NAME}_transformer():
    return {NAME}Transform
'''


COMPILER_FACTORY = '''
def get_{NAME}_compiler(grammar_name="{NAME}", 
                        grammar_source=""):
    global thread_local_{NAME}_compiler_singleton
    try:
        compiler = thread_local_{NAME}_compiler_singleton
        compiler.set_grammar_name(grammar_name, grammar_source)
        return compiler
    except NameError:
        thread_local_{NAME}_compiler_singleton = \\
            {NAME}Compiler(grammar_name, grammar_source)
        return thread_local_{NAME}_compiler_singleton 
'''

Eckhart Arnold's avatar
Eckhart Arnold committed
281

282
283
284
285
286
287
288
289
290
291
292
293
294
295
class EBNFCompilerError(Exception):
    """Error raised by `EBNFCompiler` class. (Not compilation errors
    in the strict sense, see `CompilationError` below)"""
    pass


class EBNFCompiler(CompilerBase):
    """Generates a Parser from an abstract syntax tree of a grammar specified
    in EBNF-Notation.
    """
    COMMENT_KEYWORD = "COMMENT__"
    RESERVED_SYMBOLS = {TOKEN_KEYWORD, WHITESPACE_KEYWORD, COMMENT_KEYWORD}
    AST_ERROR = "Badly structured syntax tree. " \
                "Potentially due to erroneuos AST transformation."
296
297
298
299
    PREFIX_TABLE = {'§': 'Required',
                    '&': 'Lookahead', '!': 'NegativeLookahead',
                    '-&': 'Lookbehind', '-!': 'NegativeLookbehind',
                    '::': 'Pop', ':': 'Retrieve'}
300
301
302
    WHITESPACE = {'horizontal': r'[\t ]*',  # default: horizontal
                  'linefeed': r'[ \t]*\n?(?!\s*\n)[ \t]*',
                  'vertical': r'\s*'}
303

304
    def __init__(self, grammar_name="", grammar_source=""):
Eckhart Arnold's avatar
Eckhart Arnold committed
305
        super(EBNFCompiler, self).__init__(grammar_name, grammar_source)
306
307
308
        self._reset()

    def _reset(self):
Eckhart Arnold's avatar
Eckhart Arnold committed
309
        self._result = None
310
311
        self.rules = set()
        self.variables = set()
312
        self.symbol_nodes = []
313
314
315
        self.definition_names = []
        self.recursive = set()
        self.root = ""
316
        self.directives = {'whitespace': self.WHITESPACE['horizontal'],
317
                           'comment': '',
318
                           'literalws': ['right'],
319
                           'tokens': set(),     # alt. 'scanner_tokens'
320
                           'counterpart': set()}     # alt. 'retrieve_counterpart'
321

Eckhart Arnold's avatar
Eckhart Arnold committed
322
323
324
325
    @property
    def result(self):
        return self._result

326
327
    def gen_scanner_skeleton(self):
        name = self.grammar_name + "Scanner"
328
329
        return "def %s(text):\n    return text\n" % name \
               + SCANNER_FACTORY.format(NAME=self.grammar_name)
330

331
    def gen_transformer_skeleton(self):
332
        if not self.definition_names:
Eckhart Arnold's avatar
Eckhart Arnold committed
333
334
            raise EBNFCompilerError('Compiler must be run before calling '
                                    '"gen_transformer_Skeleton()"!')
335
336
        tt_name = self.grammar_name + '_AST_transformation_table'
        tf_name = self.grammar_name + 'Transform'
di68kap's avatar
di68kap committed
337
        transtable = [tt_name + ' = {',
338
339
340
                      '    # AST Transformations for the ' +
                      self.grammar_name + '-grammar']
        for name in self.definition_names:
di68kap's avatar
di68kap committed
341
            transtable.append('    "' + name + '": no_operation,')
342
343
        transtable += ['    "": no_operation', '}', '',  tf_name +
                       ' = partial(traverse, processing_table=%s)' % tt_name, '']
344
        transtable += [TRANSFORMER_FACTORY.format(NAME=self.grammar_name)]
345
346
347
348
349
350
351
352
353
354
355
        return '\n'.join(transtable)

    def gen_compiler_skeleton(self):
        if not self.definition_names:
            raise EBNFCompilerError('Compiler has not been run before calling '
                                    '"gen_Compiler_Skeleton()"!')
        compiler = ['class ' + self.grammar_name + 'Compiler(CompilerBase):',
                    '    """Compiler for the abstract-syntax-tree of a ' +
                    self.grammar_name + ' source file.',
                    '    """', '',
                    '    def __init__(self, grammar_name="' +
Eckhart Arnold's avatar
Eckhart Arnold committed
356
                    self.grammar_name + '", grammar_source=""):',
357
                    '        super(' + self.grammar_name +
Eckhart Arnold's avatar
Eckhart Arnold committed
358
                    'Compiler, self).__init__(grammar_name, grammar_source)',
359
360
                    "        assert re.match('\w+\Z', grammar_name)", '']
        for name in self.definition_names:
361
            method_name = CompilerBase.derive_method_name(name)
362
            if name == self.root:
363
                compiler += ['    def ' + method_name + '(self, node):',
364
365
                             '        return node', '']
            else:
366
                compiler += ['    def ' + method_name + '(self, node):',
367
                             '        pass', '']
368
        compiler += [COMPILER_FACTORY.format(NAME=self.grammar_name)]
369
        return '\n'.join(compiler)
370

Eckhart Arnold's avatar
Eckhart Arnold committed
371
    def assemble_parser(self, definitions):
372
        # fix capture of variables that have been defined before usage [sic!]
373

374
375
376
        if self.variables:
            for i in range(len(definitions)):
                if definitions[i][0] in self.variables:
377
                    definitions[i] = (definitions[i][0], 'Capture(%s)' % definitions[1])
378
379

        self.definition_names = [defn[0] for defn in definitions]
Eckhart Arnold's avatar
Eckhart Arnold committed
380
381
382
383
        definitions.append(('wspR__', WHITESPACE_KEYWORD
                            if 'right' in self.directives['literalws'] else "''"))
        definitions.append(('wspL__', WHITESPACE_KEYWORD
                            if 'left' in self.directives['literalws'] else "''"))
384
385
386
387
388
389
390
391
        definitions.append((WHITESPACE_KEYWORD,
                            ("mixin_comment(whitespace="
                             "r'{whitespace}', comment=r'{comment}')").
                            format(**self.directives)))
        definitions.append((self.COMMENT_KEYWORD, "r'{comment}'".format(**self.directives)))

        # prepare parser class header and docstring and
        # add EBNF grammar to the doc string of the parser class
392

393
        article = 'an ' if self.grammar_name[0:1] in "AaEeIiOoUu" else 'a '  # what about 'hour', 'universe' etc.?
394
395
396
397
        declarations = ['class ' + self.grammar_name +
                        'Grammar(GrammarBase):',
                        'r"""Parser for ' + article + self.grammar_name +
                        ' source file' +
398
                        (', with this grammar:' if self.grammar_source else '.')]
399
        definitions.append(('parser_initialization__', '"upon instatiation"'))
400
        if self.grammar_source:
401
            definitions.append(('source_hash__',
402
                                '"%s"' % md5(self.grammar_source, __version__)))
403
            declarations.append('')
404
            declarations += [line for line in self.grammar_source.split('\n')]
405
406
407
408
            while declarations[-1].strip() == '':
                declarations = declarations[:-1]
        declarations.append('"""')

409
        # add default functions for counterpart filters of pop or retrieve operators
410

411
412
413
414
415
416
        for symbol in self.directives['counterpart']:
            # declarations.append('def %s_counterpart(value): \n' % symbol +
            #                     '        return value.replace("(", ")").replace("[", "]")'
            #                     '.replace("{", "}").replace(">", "<")\n')
            declarations.append(symbol + '_counterpart = lambda value: value.replace("(", ")")'
                                '.replace("[", "]").replace("{", "}").replace(">", "<")')
417

418
        # turn definitions into declarations in reverse order
419

420
421
422
423
424
425
426
427
428
        self.root = definitions[0][0] if definitions else ""
        definitions.reverse()
        declarations += [symbol + ' = Forward()'
                         for symbol in sorted(list(self.recursive))]
        for symbol, statement in definitions:
            if symbol in self.recursive:
                declarations += [symbol + '.set(' + statement + ')']
            else:
                declarations += [symbol + ' = ' + statement]
429
        for nd in self.symbol_nodes:
430
431
            if nd.result not in self.rules:
                nd.add_error("Missing production for symbol '%s'" % nd.result)
432
        if self.root and 'root__' not in self.rules:
433
434
            declarations.append('root__ = ' + self.root)
        declarations.append('')
Eckhart Arnold's avatar
Eckhart Arnold committed
435
436
437
        self._result = '\n    '.join(declarations) \
                       + GRAMMAR_FACTORY.format(NAME=self.grammar_name)
        return self._result
438

439
    def on_syntax(self, node):
440
441
442
443
        self._reset()
        definitions = []

        # drop the wrapping sequence node
444
        if len(node.children) == 1 and not node.result[0].parser.name:
445
446
447
448
449
            node = node.result[0]

        # compile definitions and directives and collect definitions
        for nd in node.result:
            if nd.parser.name == "definition":
450
                definitions.append(self._compile(nd))
451
452
            else:
                assert nd.parser.name == "directive", nd.as_sexpr()
453
                self._compile(nd)
454

Eckhart Arnold's avatar
Eckhart Arnold committed
455
        return self.assemble_parser(definitions)
456

457
    def on_definition(self, node):
458
        rule = node.result[0].result
459
460
461
        if rule in self.rules:
            node.add_error('A rule with name "%s" has already been defined.' % rule)
        elif rule in EBNFCompiler.RESERVED_SYMBOLS:
462
463
464
465
            node.add_error('Symbol "%s" is a reserved symbol.' % rule)
        elif not sane_parser_name(rule):
            node.add_error('Illegal symbol "%s". Symbols must not start or '
                           ' end with a doube underscore "__".' % rule)
466
        elif rule in self.directives['tokens']:
467
468
469
470
471
472
473
            node.add_error('Symbol "%s" has already been defined as '
                           'a scanner token.' % rule)
        elif keyword.iskeyword(rule):
            node.add_error('Python keyword "%s" may not be used as a symbol. '
                           % rule + '(This may change in the furute.)')
        try:
            self.rules.add(rule)
474
            defn = self._compile(node.result[1])
475
            if rule in self.variables:
476
                defn = 'Capture(%s)' % defn
477
478
479
480
481
                self.variables.remove(rule)
        except TypeError as error:
            errmsg = EBNFCompiler.AST_ERROR + " (" + str(error) + ")\n" + node.as_sexpr()
            node.add_error(errmsg)
            rule, defn = rule + ':error', '"' + errmsg + '"'
Eckhart Arnold's avatar
Eckhart Arnold committed
482
        return rule, defn
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497

    @staticmethod
    def _check_rx(node, rx):
        """Checks whether the string `rx` represents a valid regular
        expression. Makes sure that multiline regular expressions are
        prepended by the multiline-flag. Returns the regular expression string.
        """
        rx = rx if rx.find('\n') < 0 or rx[0:4] == '(?x)' else '(?x)' + rx
        try:
            re.compile(rx)
        except Exception as re_error:
            node.add_error("malformed regular expression %s: %s" %
                           (repr(rx), str(re_error)))
        return rx

498
    def on_directive(self, node):
499
        key = node.result[0].result.lower()
500
        assert key not in self.directives['tokens']
501
        if key in {'comment', 'whitespace'}:
502
503
            if node.result[1].parser.name == "list_":
                if len(node.result[1].result) != 1:
Eckhart Arnold's avatar
Eckhart Arnold committed
504
                    node.add_error('Directive "%s" must have one, but not %i values.' %
505
                                   (key, len(node.result[1])))
506
                value = self._compile(node.result[1]).pop()
507
508
                if key == 'whitespace' and value in EBNFCompiler.WHITESPACE:
                    value = EBNFCompiler.WHITESPACE[value]  # replace whitespace-name by regex
509
                else:
510
                    node.add_error('Value "%s" not allowed for directive "%s".' % (value, key))
511
            else:
512
513
514
515
516
517
518
519
                value = node.result[1].result.strip("~")
                if value != node.result[1].result:
                    node.add_error("Whitespace marker '~' not allowed in definition of "
                                   "%s regular expression." % key)
                if value[0] + value[-1] in {'""', "''"}:
                    value = escape_re(value[1:-1])
                elif value[0] + value[-1] == '//':
                    value = self._check_rx(node, value[1:-1])
520
521
522
                if key == 'whitespace' and not re.match(value, ''):
                    node.add_error("Implicit whitespace should always match the empty string, "
                                   "/%s/ does not." % value)
523
            self.directives[key] = value
524

525
        elif key == 'literalws':
526
            value = {item.lower() for item in self._compile(node.result[1])}
527
            if (len(value - {'left', 'right', 'both', 'none'}) > 0
Eckhart Arnold's avatar
Eckhart Arnold committed
528
                    or ('none' in value and len(value) > 1)):
529
530
531
532
533
534
535
                node.add_error('Directive "literalws" allows the values '
                               '`left`, `right`, `both` or `none`, '
                               'but not `%s`' % ", ".join(value))
            ws = {'left', 'right'} if 'both' in value \
                else {} if 'none' in value else value
            self.directives[key] = list(ws)

536
        elif key in {'tokens', 'scanner_tokens'}:
537
            self.directives['tokens'] |= self._compile(node.result[1])
538

539
        elif key in {'counterpart', 'retrieve_counterpart'}:
540
            self.directives['counterpart'] |= self._compile(node.result[1])
541

542
543
544
        else:
            node.add_error('Unknown directive %s ! (Known ones are %s .)' %
                           (key,
545
                            ', '.join(list(self.directives.keys()))))
546
547
        return ""

548
    def non_terminal(self, node, parser_class, custom_args=[]):
549
550
551
        """Compiles any non-terminal, where `parser_class` indicates the Parser class
        name for the particular non-terminal.
        """
552
        arguments = [self._compile(r) for r in node.result] + custom_args
553
554
        return parser_class + '(' + ', '.join(arguments) + ')'

555
    def on_expression(self, node):
556
557
        return self.non_terminal(node, 'Alternative')

558
    def on_term(self, node):
559
560
        return self.non_terminal(node, 'Sequence')

561
    def on_factor(self, node):
562
563
564
        assert node.children
        assert len(node.result) >= 2, node.as_sexpr()
        prefix = node.result[0].result
565
        custom_args = []
566
567
568

        if prefix in {'::', ':'}:
            assert len(node.result) == 2
569
            arg = node.result[-1]
570
            if arg.parser.name != 'symbol':
Eckhart Arnold's avatar
Eckhart Arnold committed
571
                node.add_error(('Retrieve Operator "%s" requires a symbol, '
572
573
                                'and not a %s.') % (prefix, str(arg.parser)))
                return str(arg.result)
574
575
            if str(arg) in self.directives['counterpart']:
                custom_args = ['counterpart=%s_counterpart' % str(arg)]
576
577
            self.variables.add(arg.result)

578
        elif len(node.result) > 2:
579
580
            # shift = (Node(node.parser, node.result[1].result),)
            # node.result[1].result = shift + node.result[2:]
581
            node.result[1].result = (Node(node.result[1].parser, node.result[1].result),) \
582
583
584
585
586
                                    + node.result[2:]
            node.result[1].parser = node.parser
            node.result = (node.result[0], node.result[1])

        node.result = node.result[1:]
587
588
589
590
591
        try:
            parser_class = self.PREFIX_TABLE[prefix]
            return self.non_terminal(node, parser_class, custom_args)
        except KeyError:
            node.add_error('Unknown prefix "%s".' % prefix)
592

593
    def on_option(self, node):
594
595
        return self.non_terminal(node, 'Optional')

596
    def on_repetition(self, node):
597
598
        return self.non_terminal(node, 'ZeroOrMore')

599
    def on_oneormore(self, node):
600
601
        return self.non_terminal(node, 'OneOrMore')

602
    def on_regexchain(self, node):
603
604
        raise EBNFCompilerError("Not yet implemented!")

605
    def on_group(self, node):
606
607
608
        raise EBNFCompilerError("Group nodes should have been eliminated by "
                                "AST transformation!")

609
    def on_symbol(self, node):
610
        if node.result in self.directives['tokens']:
611
612
            return 'ScannerToken("' + node.result + '")'
        else:
613
            self.symbol_nodes.append(node)
614
615
616
617
            if node.result in self.rules:
                self.recursive.add(node.result)
            return node.result

618
    def on_literal(self, node):
619
        return 'Token(' + node.result.replace('\\', r'\\') + ')'  # return 'Token(' + ', '.join([node.result]) + ')' ?
620

621
    def on_regexp(self, node):
622
623
624
625
626
627
628
629
630
        rx = node.result
        name = []
        if rx[:2] == '~/':
            if not 'left' in self.directives['literalws']:
                name = ['wL=' + WHITESPACE_KEYWORD] + name
            rx = rx[1:]
        elif 'left' in self.directives['literalws']:
            name = ["wL=''"] + name
        if rx[-2:] == '/~':
Eckhart Arnold's avatar
Eckhart Arnold committed
631
            if 'right' not in self.directives['literalws']:
632
633
634
635
636
637
638
639
640
641
642
643
644
                name = ['wR=' + WHITESPACE_KEYWORD] + name
            rx = rx[:-1]
        elif 'right' in self.directives['literalws']:
            name = ["wR=''"] + name
        try:
            arg = repr(self._check_rx(node, rx[1:-1].replace(r'\/', '/')))
        except AttributeError as error:
            errmsg = EBNFCompiler.AST_ERROR + " (" + str(error) + ")\n" + \
                     node.as_sexpr()
            node.add_error(errmsg)
            return '"' + errmsg + '"'
        return 'RE(' + ', '.join([arg] + name) + ')'

645
    def on_list_(self, node):
646
647
        assert node.children
        return set(item.result.strip() for item in node.result)
648
649


Eckhart Arnold's avatar
Eckhart Arnold committed
650
651
652
653
654
655
656
657
658
def get_ebnf_compiler(grammar_name="", grammar_source=""):
    global thread_local_ebnf_compiler_singleton
    try:
        compiler = thread_local_ebnf_compiler_singleton
        compiler.set_grammar_name(grammar_name, grammar_source)
        return compiler
    except NameError:
        thread_local_ebnf_compiler_singleton = EBNFCompiler(grammar_name, grammar_source)
        return thread_local_ebnf_compiler_singleton