ebnf.py 26 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
Eckhart Arnold's avatar
Eckhart Arnold committed
34
from .versionnumber import __version__
35
36


Eckhart Arnold's avatar
Eckhart Arnold committed
37
__all__ = ['EBNFGrammar',
38
           'EBNFTransform',
Eckhart Arnold's avatar
Eckhart Arnold committed
39
           'EBNFCompilerError',
40
41
           'EBNFCompiler',
           'grammar_changed']
42
43


Eckhart Arnold's avatar
Eckhart Arnold committed
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63


########################################################################
#
# EBNF scanning
#
########################################################################


def get_ebnf_scanner():
    return nil_scanner


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


64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
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
83
                | [flowmarker] regexchain
84
85
86
87
88
89
90
91
92
                | [flowmarker] oneormore
                | repetition
                | option

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

    group      =  "(" expression §")"
93
    regexchain =  "<" expression §">"                # compiles "expression" into a singular regular expression
94
95
    oneormore  =  "{" expression "}+"
    repetition =  "{" expression §"}"
96
97
    option     =  "[" expression §"]"

98
99
100
101
102
103
    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|$)/~
                                                     # '~' is a whitespace-marker, if present leading or trailing
                                                     # whitespace of a regular expression will be ignored tacitly.
104
    list_      =  /\w+/~ { "," /\w+/~ }              # comma separated list of symbols, e.g. BEGIN_LIST, END_LIST,
105
106
107
108
                                                     # BEGIN_QUOTE, END_QUOTE ; see CommonMark/markdown.py for an exmaple
    EOF =  !/./
    """
    expression = Forward()
109
    source_hash__ = "a410e1727fb7575e98ff8451dbf8f3bd"
110
    parser_initialization__ = "upon instatiation"
111
112
    COMMENT__ = r'#.*(?:\n|$)'
    WSP__ = mixin_comment(whitespace=r'\s*', comment=r'#.*(?:\n|$)')
113
    wspL__ = ''
114
    wspR__ = WSP__
115
    EOF = NegativeLookahead(RE('.', wR=''))
116
    list_ = Sequence(RE('\\w+'), ZeroOrMore(Sequence(Token(","), RE('\\w+'))))
117
118
119
    regexp = RE('~?/(?:[^/]|(?<=\\\\)/)*/~?')
    literal = Alternative(RE('"(?:[^"]|\\\\")*?"'), RE("'(?:[^']|\\\\')*?'"))
    symbol = RE('(?!\\d)\\w+')
120
    option = Sequence(Token("["), expression, Required(Token("]")))
121
122
    repetition = Sequence(Token("{"), expression, Required(Token("}")))
    oneormore = Sequence(Token("{"), expression, Token("}+"))
123
    regexchain = Sequence(Token("<"), expression, Required(Token(">")))
124
125
126
127
128
    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),
129
130
                         Sequence(Optional(flowmarker), group), Sequence(Optional(flowmarker), regexchain),
                         Sequence(Optional(flowmarker), oneormore), repetition, option)
131
132
133
134
    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)
135
    syntax = Sequence(Optional(RE('', wR='', wL=WSP__)), ZeroOrMore(Alternative(definition, directive)), Required(EOF))
136
137
138
    root__ = syntax


Eckhart Arnold's avatar
Eckhart Arnold committed
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
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
#
########################################################################


187
188
#TODO: Add Capture and Retrieve Validation: A variable mustn't be captured twice before retrival?!?

189
EBNF_transformation_table = {
190
191
192
193
194
195
196
197
198
199
200
201
202
    # AST Transformations for EBNF-grammar
    "syntax":
        remove_expendables,
    "directive, definition":
        partial(remove_tokens, tokens={'@', '='}),
    "expression, chain":
        [replace_by_single_child, flatten,
         partial(remove_tokens, tokens={'|', '--'})],
    "term":
        [replace_by_single_child, flatten],  # supports both idioms:  "{ factor }+" and "factor { factor }"
    "factor, flowmarker, retrieveop":
        replace_by_single_child,
    "group":
203
204
205
        [remove_enclosing_delimiters, replace_by_single_child],
    "oneormore, repetition, option, regexchain":
        [reduce_single_child, remove_enclosing_delimiters],
206
    "symbol, literal, regexp":
207
208
209
        [remove_expendables, reduce_single_child],
    (TOKEN_KEYWORD, WHITESPACE_KEYWORD):
        [remove_expendables, reduce_single_child],
210
    "list_":
211
        [flatten, partial(remove_tokens, tokens={','})],
212
213
214
215
    "":
        [remove_expendables, replace_by_single_child]
}

216

217
EBNF_validation_table = {
218
219
220
221
222
    # Semantic validation on the AST
    "repetition, option, oneormore":
        [partial(forbid, child_tags=['repetition', 'option', 'oneormore']),
         partial(assert_content, regex=r'(?!§)')],
}
223

224

225
226
227
def EBNFTransform(syntax_tree):
    for processing_table in [EBNF_transformation_table, EBNF_validation_table]:
        traverse(syntax_tree, processing_table)
di68kap's avatar
di68kap committed
228
229


Eckhart Arnold's avatar
Eckhart Arnold committed
230
231
232
233
234
235
236
237
238
239
240
def get_ebnf_transformer():
    return EBNFTransform


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


241
242
243
244
245
246
247
248
249
250
251
252
253
254
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."
255
256
257
258
    PREFIX_TABLE = {'§': 'Required',
                    '&': 'Lookahead', '!': 'NegativeLookahead',
                    '-&': 'Lookbehind', '-!': 'NegativeLookbehind',
                    '::': 'Pop', ':': 'Retrieve'}
259
260
261
    WHITESPACE = {'horizontal': r'[\t ]*',  # default: horizontal
                  'linefeed': r'[ \t]*\n?(?!\s*\n)[ \t]*',
                  'vertical': r'\s*'}
262

263
    def __init__(self, grammar_name="", grammar_source=""):
Eckhart Arnold's avatar
Eckhart Arnold committed
264
        super(EBNFCompiler, self).__init__(grammar_name, grammar_source)
265
266
267
268
269
        self._reset()

    def _reset(self):
        self.rules = set()
        self.variables = set()
270
        self.symbol_nodes = []
271
272
273
        self.definition_names = []
        self.recursive = set()
        self.root = ""
274
        self.directives = {'whitespace': self.WHITESPACE['horizontal'],
275
                           'comment': '',
276
                           'literalws': ['right'],
277
                           'tokens': set(),     # alt. 'scanner_tokens'
278
                           'counterpart': set()}     # alt. 'retrieve_counterpart'
279
280
281
282
283
284
285
286
287

    def gen_scanner_skeleton(self):
        name = self.grammar_name + "Scanner"
        return "def %s(text):\n    return text\n" % name

    def gen_AST_skeleton(self):
        if not self.definition_names:
            raise EBNFCompilerError('Compiler has not been run before calling '
                                    '"gen_AST_Skeleton()"!')
288
289
        tt_name = self.grammar_name + '_AST_transformation_table'
        tf_name = self.grammar_name + 'Transform'
di68kap's avatar
di68kap committed
290
        transtable = [tt_name + ' = {',
291
292
293
                      '    # AST Transformations for the ' +
                      self.grammar_name + '-grammar']
        for name in self.definition_names:
di68kap's avatar
di68kap committed
294
            transtable.append('    "' + name + '": no_operation,')
295
296
        transtable += ['    "": no_operation', '}', '',  tf_name +
                       ' = partial(traverse, processing_table=%s)' % tt_name, '']
297
298
299
300
301
302
303
304
305
306
307
        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
308
                    self.grammar_name + '", grammar_source=""):',
309
                    '        super(' + self.grammar_name +
Eckhart Arnold's avatar
Eckhart Arnold committed
310
                    'Compiler, self).__init__(grammar_name, grammar_source)',
311
312
                    "        assert re.match('\w+\Z', grammar_name)", '']
        for name in self.definition_names:
313
            method_name = CompilerBase.derive_method_name(name)
314
            if name == self.root:
315
                compiler += ['    def ' + method_name + '(self, node):',
316
317
                             '        return node', '']
            else:
318
                compiler += ['    def ' + method_name + '(self, node):',
319
                             '        pass', '']
320
        return '\n'.join(compiler)
321
322
323
324
325
326

    def gen_parser(self, definitions):
        # fix capture of variables that have been defined before usage [sic!]
        if self.variables:
            for i in range(len(definitions)):
                if definitions[i][0] in self.variables:
327
                    definitions[i] = (definitions[i][0], 'Capture(%s)' % definitions[1])
328
329

        self.definition_names = [defn[0] for defn in definitions]
Eckhart Arnold's avatar
Eckhart Arnold committed
330
331
332
333
        definitions.append(('wspR__', WHITESPACE_KEYWORD
                            if 'right' in self.directives['literalws'] else "''"))
        definitions.append(('wspL__', WHITESPACE_KEYWORD
                            if 'left' in self.directives['literalws'] else "''"))
334
335
336
337
338
339
340
341
        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
342
        article = 'an ' if self.grammar_name[0:1] in "AaEeIiOoUu" else 'a '  # what about 'hour', 'universe' etc.?
343
344
345
346
        declarations = ['class ' + self.grammar_name +
                        'Grammar(GrammarBase):',
                        'r"""Parser for ' + article + self.grammar_name +
                        ' source file' +
347
                        (', with this grammar:' if self.grammar_source else '.')]
348
        definitions.append(('parser_initialization__', '"upon instatiation"'))
349
        if self.grammar_source:
350
            definitions.append(('source_hash__',
351
                                '"%s"' % md5(self.grammar_source, __version__)))
352
            declarations.append('')
353
            declarations += [line for line in self.grammar_source.split('\n')]
354
355
356
357
            while declarations[-1].strip() == '':
                declarations = declarations[:-1]
        declarations.append('"""')

358
359
360
361
362
363
364
        # add default functions for counterpart filters of pop or retrieve operators
        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(">", "<")')
365

366
367
368
369
370
371
372
373
374
375
        # turn definitions into declarations in reverse order
        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]
376
        for nd in self.symbol_nodes:
377
378
            if nd.result not in self.rules:
                nd.add_error("Missing production for symbol '%s'" % nd.result)
379
        if self.root and 'root__' not in self.rules:
380
381
382
383
            declarations.append('root__ = ' + self.root)
        declarations.append('')
        return '\n    '.join(declarations)

384
    def on_syntax(self, node):
385
386
387
388
389
390
391
392
393
394
395
        self._reset()
        definitions = []

        # drop the wrapping sequence node
        if isinstance(node.parser, Sequence) and \
                isinstance(node.result[0].parser, ZeroOrMore):
            node = node.result[0]

        # compile definitions and directives and collect definitions
        for nd in node.result:
            if nd.parser.name == "definition":
396
                definitions.append(self._compile(nd))
397
398
            else:
                assert nd.parser.name == "directive", nd.as_sexpr()
399
                self._compile(nd)
400
401
402

        return self.gen_parser(definitions)

403
    def on_definition(self, node):
404
        rule = node.result[0].result
405
406
407
        if rule in self.rules:
            node.add_error('A rule with name "%s" has already been defined.' % rule)
        elif rule in EBNFCompiler.RESERVED_SYMBOLS:
408
409
410
411
            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)
412
        elif rule in self.directives['tokens']:
413
414
415
416
417
418
419
            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)
420
            defn = self._compile(node.result[1])
421
            if rule in self.variables:
422
                defn = 'Capture(%s)' % defn
423
424
425
426
427
                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
428
        return rule, defn
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443

    @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

444
    def on_directive(self, node):
445
        key = node.result[0].result.lower()
446
        assert key not in self.directives['tokens']
447
        if key in {'comment', 'whitespace'}:
448
449
            if node.result[1].parser.name == "list_":
                if len(node.result[1].result) != 1:
Eckhart Arnold's avatar
Eckhart Arnold committed
450
                    node.add_error('Directive "%s" must have one, but not %i values.' %
451
                                   (key, len(node.result[1])))
452
                value = self._compile(node.result[1]).pop()
453
454
                if key == 'whitespace' and value in EBNFCompiler.WHITESPACE:
                    value = EBNFCompiler.WHITESPACE[value]  # replace whitespace-name by regex
455
                else:
456
                    node.add_error('Value "%s" not allowed for directive "%s".' % (value, key))
457
            else:
458
459
460
461
462
463
464
465
                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])
466
467
468
                if key == 'whitespace' and not re.match(value, ''):
                    node.add_error("Implicit whitespace should always match the empty string, "
                                   "/%s/ does not." % value)
469
            self.directives[key] = value
470

471
        elif key == 'literalws':
472
            value = {item.lower() for item in self._compile(node.result[1])}
473
            if (len(value - {'left', 'right', 'both', 'none'}) > 0
Eckhart Arnold's avatar
Eckhart Arnold committed
474
                    or ('none' in value and len(value) > 1)):
475
476
477
478
479
480
481
                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)

482
        elif key in {'tokens', 'scanner_tokens'}:
483
            self.directives['tokens'] |= self._compile(node.result[1])
484

485
        elif key in {'counterpart', 'retrieve_counterpart'}:
486
            self.directives['counterpart'] |= self._compile(node.result[1])
487

488
489
490
        else:
            node.add_error('Unknown directive %s ! (Known ones are %s .)' %
                           (key,
491
                            ', '.join(list(self.directives.keys()))))
492
493
        return ""

494
    def non_terminal(self, node, parser_class, custom_args=[]):
495
496
497
        """Compiles any non-terminal, where `parser_class` indicates the Parser class
        name for the particular non-terminal.
        """
498
        arguments = [self._compile(r) for r in node.result] + custom_args
499
500
        return parser_class + '(' + ', '.join(arguments) + ')'

501
    def on_expression(self, node):
502
503
        return self.non_terminal(node, 'Alternative')

504
    def on_term(self, node):
505
506
        return self.non_terminal(node, 'Sequence')

507
    def on_factor(self, node):
508
509
510
511
        assert isinstance(node.parser, Sequence), node.as_sexpr()  # these assert statements can be removed
        assert node.children
        assert len(node.result) >= 2, node.as_sexpr()
        prefix = node.result[0].result
512
        custom_args = []
513
514
515

        if prefix in {'::', ':'}:
            assert len(node.result) == 2
516
            arg = node.result[-1]
517
            if arg.parser.name != 'symbol':
Eckhart Arnold's avatar
Eckhart Arnold committed
518
                node.add_error(('Retrieve Operator "%s" requires a symbol, '
519
520
                                'and not a %s.') % (prefix, str(arg.parser)))
                return str(arg.result)
521
522
            if str(arg) in self.directives['counterpart']:
                custom_args = ['counterpart=%s_counterpart' % str(arg)]
523
524
            self.variables.add(arg.result)

525
        elif len(node.result) > 2:
526
527
            # shift = (Node(node.parser, node.result[1].result),)
            # node.result[1].result = shift + node.result[2:]
528
            node.result[1].result = (Node(node.result[1].parser, node.result[1].result),) \
529
530
531
532
533
                                    + node.result[2:]
            node.result[1].parser = node.parser
            node.result = (node.result[0], node.result[1])

        node.result = node.result[1:]
534
535
536
537
538
        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)
539

540
    def on_option(self, node):
541
542
        return self.non_terminal(node, 'Optional')

543
    def on_repetition(self, node):
544
545
        return self.non_terminal(node, 'ZeroOrMore')

546
    def on_oneormore(self, node):
547
548
        return self.non_terminal(node, 'OneOrMore')

549
    def on_regexchain(self, node):
550
551
        raise EBNFCompilerError("Not yet implemented!")

552
    def on_group(self, node):
553
554
555
        raise EBNFCompilerError("Group nodes should have been eliminated by "
                                "AST transformation!")

556
    def on_symbol(self, node):
557
        if node.result in self.directives['tokens']:
558
559
            return 'ScannerToken("' + node.result + '")'
        else:
560
            self.symbol_nodes.append(node)
561
562
563
564
            if node.result in self.rules:
                self.recursive.add(node.result)
            return node.result

565
    def on_literal(self, node):
566
        return 'Token(' + node.result.replace('\\', r'\\') + ')'  # return 'Token(' + ', '.join([node.result]) + ')' ?
567

568
    def on_regexp(self, node):
569
570
571
572
573
574
575
576
577
        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
578
            if 'right' not in self.directives['literalws']:
579
580
581
582
583
584
585
586
587
588
589
590
591
                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) + ')'

592
    def on_list_(self, node):
593
594
        assert node.children
        return set(item.result.strip() for item in node.result)
595
596


Eckhart Arnold's avatar
Eckhart Arnold committed
597
598
599
600
601
602
603
604
605
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