ebnf.py 59.1 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
# ebnf.py - EBNF -> Python-Parser compilation for DHParser
#
# 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.
17
18


19
20
21
22
23
"""
Module ``ebnf`` provides a self-hosting parser for EBNF-Grammars as
well as an EBNF-compiler that compiles an EBNF-Grammar into a
DHParser based Grammar class that can be executed to parse source text
conforming to this grammar into contrete syntax trees.
24
25
"""

26

27
from collections import OrderedDict
28
from functools import partial
eckhart's avatar
eckhart committed
29
30
import keyword
import os
Eckhart Arnold's avatar
Eckhart Arnold committed
31
from typing import Callable, Dict, List, Set, Tuple, Sequence, Union, Optional, Any, cast
32

eckhart's avatar
eckhart committed
33
from DHParser.compile import CompilerError, Compiler, compile_source, visitor_name
34
from DHParser.error import Error
35
from DHParser.parse import Grammar, mixin_comment, Forward, RegExp, DropWhitespace, \
36
37
    NegativeLookahead, Alternative, Series, Option, OneOrMore, ZeroOrMore, Token, \
    GrammarError
38
from DHParser.preprocess import nil_preprocessor, PreprocessorFunc
eckhart's avatar
eckhart committed
39
from DHParser.syntaxtree import Node, WHITESPACE_PTYPE, TOKEN_PTYPE
eckhart's avatar
eckhart committed
40
from DHParser.toolkit import load_if_file, escape_re, md5, sane_parser_name, re, expand_table, \
Eckhart Arnold's avatar
Eckhart Arnold committed
41
    GLOBALS, get_config_value, unrepr, compile_python_object
eckhart's avatar
eckhart committed
42
from DHParser.transform import TransformationFunc, traverse, remove_brackets, \
Eckhart Arnold's avatar
Eckhart Arnold committed
43
    reduce_single_child, replace_by_single_child, remove_whitespace, remove_empty, \
eckhart's avatar
eckhart committed
44
    remove_tokens, flatten, forbid, assert_content
45
from DHParser.versionnumber import __version__
Eckhart Arnold's avatar
Eckhart Arnold committed
46

eckhart's avatar
eckhart committed
47

48
__all__ = ('get_ebnf_preprocessor',
49
50
51
52
           'get_ebnf_grammar',
           'get_ebnf_transformer',
           'get_ebnf_compiler',
           'EBNFGrammar',
53
           'EBNFTransform',
Eckhart Arnold's avatar
Eckhart Arnold committed
54
           'EBNFCompilerError',
55
           'EBNFCompiler',
56
           'grammar_changed',
eckhart's avatar
eckhart committed
57
           'compile_ebnf',
58
           'PreprocessorFactoryFunc',
59
60
           'ParserFactoryFunc',
           'TransformerFactoryFunc',
61
           'CompilerFactoryFunc')
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
########################################################################
#
# source code support
#
########################################################################


dhparserdir = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))


DHPARSER_IMPORTS = '''
import collections
from functools import partial
import os
import sys

sys.path.append(r'{dhparserdir}')

try:
    import regex as re
except ImportError:
    import re
from DHParser import logging, is_filename, load_if_file, \\
    Grammar, Compiler, nil_preprocessor, PreprocessorToken, Whitespace, DropWhitespace, \\
    Lookbehind, Lookahead, Alternative, Pop, Token, DropToken, Synonym, AllOf, SomeOf, \\
    Unordered, Option, NegativeLookbehind, OneOrMore, RegExp, Retrieve, Series, Capture, \\
    ZeroOrMore, Forward, NegativeLookahead, Required, mixin_comment, compile_source, \\
eckhart's avatar
eckhart committed
91
    grammar_changed, last_value, counterpart, PreprocessorFunc, is_empty, \\
92
93
94
    Node, TransformationFunc, TransformationDict, transformation_factory, traverse, \\
    remove_children_if, move_adjacent, normalize_whitespace, is_anonymous, matches_re, \\
    reduce_single_child, replace_by_single_child, replace_or_reduce, remove_whitespace, \\
di68kap's avatar
di68kap committed
95
    replace_by_children, remove_empty, remove_tokens, flatten, is_insignificant_whitespace, \\
Eckhart Arnold's avatar
Eckhart Arnold committed
96
97
    collapse, collapse_if, replace_content, WHITESPACE_PTYPE, TOKEN_PTYPE, \\
    remove_nodes, remove_content, remove_brackets, change_tag_name, remove_anonymous_tokens, \\
98
99
100
    keep_children, is_one_of, not_one_of, has_content, apply_if, remove_first, remove_last, \\
    remove_anonymous_empty, keep_nodes, traverse_locally, strip, lstrip, rstrip, \\
    replace_content, replace_content_by, forbid, assert_content, remove_infix_operator, \\
101
    error_on, recompile_grammar, left_associative, lean_left, GLOBALS
102
'''.format(dhparserdir=dhparserdir)
103
104


Eckhart Arnold's avatar
Eckhart Arnold committed
105
106
107
108
109
110
111
########################################################################
#
# EBNF scanning
#
########################################################################


112
def get_ebnf_preprocessor() -> PreprocessorFunc:
eckhart's avatar
eckhart committed
113
114
115
116
117
    """
    Returns the preprocessor function for the EBNF compiler.
    As of now, no preprocessing is needed for EBNF-sources. Therefore,
    just a dummy function is returned.
    """
118
    return nil_preprocessor
Eckhart Arnold's avatar
Eckhart Arnold committed
119
120
121
122
123
124
125
126


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

127

di68kap's avatar
di68kap committed
128
class EBNFGrammar(Grammar):
eckhart's avatar
eckhart committed
129
    r"""
eckhart's avatar
eckhart committed
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
    Parser for an EBNF source file, with this grammar:

    @ 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 | symbol) { "," (regexp | literal | symbol) }

    expression = term { "|" term }
    term       = { ["§"] factor }+                       # "§" means all following factors mandatory
    factor     = [flowmarker] [retrieveop] symbol !"="   # negative lookahead to be sure it's not a definition
               | [flowmarker] literal
               | [flowmarker] plaintext
               | [flowmarker] regexp
               | [flowmarker] whitespace
               | [flowmarker] oneormore
               | [flowmarker] group
               | [flowmarker] unordered
               | repetition
               | option

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

    group      = "(" §expression ")"
    unordered  = "<" §expression ">"                # elements of expression in arbitrary order
    oneormore  = "{" expression "}+"
    repetition = "{" §expression "}"
    option     = "[" §expression "]"

    symbol     = /(?!\d)\w+/~                       # e.g. expression, factor, parameter_list
    literal    = /"(?:[^"]|\\")*?"/~                # e.g. "(", '+', 'while'
               | /'(?:[^']|\\')*?'/~                # whitespace following literals will be ignored tacitly.
    plaintext  = /`(?:[^"]|\\")*?`/~                # like literal but does not eat whitespace
    regexp     = /\/(?:\\\/|[^\/])*?\//~            # e.g. /\w+/, ~/#.*(?:\n|$)/~
    whitespace = /~/~                               # insignificant whitespace

    EOF = !/./
171
    """
di68kap's avatar
di68kap committed
172
    expression = Forward()
eckhart's avatar
eckhart committed
173
    source_hash__ = "82a7c668f86b83f86515078e6c9093ed"
174
    static_analysis_pending__ = []
eckhart's avatar
eckhart committed
175
    parser_initialization__ = ["upon instantiation"]
di68kap's avatar
di68kap committed
176
177
    COMMENT__ = r'#.*(?:\n|$)'
    WHITESPACE__ = r'\s*'
178
    WSP_RE__ = mixin_comment(whitespace=WHITESPACE__, comment=COMMENT__)
179
    wsp__ = DropWhitespace(WSP_RE__)
di68kap's avatar
di68kap committed
180
    EOF = NegativeLookahead(RegExp('.'))
181
    whitespace = Series(RegExp('~'), wsp__)
182
    regexp = Series(RegExp('/(?:(?<!\\\\)\\\\(?:/)|[^/])*?/'), wsp__)
eckhart's avatar
eckhart committed
183
    plaintext = Series(RegExp('`(?:(?<!\\\\)\\\\`|[^`])*?`'), wsp__)
184
185
    literal = Alternative(Series(RegExp('"(?:(?<!\\\\)\\\\"|[^"])*?"'), wsp__),
                          Series(RegExp("'(?:(?<!\\\\)\\\\'|[^'])*?'"), wsp__))
186
187
188
189
190
191
192
193
194
195
    symbol = Series(RegExp('(?!\\d)\\w+'), wsp__)
    option = Series(Series(Token("["), wsp__), expression, Series(Token("]"), wsp__), mandatory=1)
    repetition = Series(Series(Token("{"), wsp__), expression, Series(Token("}"), wsp__), mandatory=1)
    oneormore = Series(Series(Token("{"), wsp__), expression, Series(Token("}+"), wsp__))
    unordered = Series(Series(Token("<"), wsp__), expression, Series(Token(">"), wsp__), mandatory=1)
    group = Series(Series(Token("("), wsp__), expression, Series(Token(")"), wsp__), mandatory=1)
    retrieveop = Alternative(Series(Token("::"), wsp__), Series(Token(":"), wsp__))
    flowmarker = Alternative(Series(Token("!"), wsp__), Series(Token("&"), wsp__),
                             Series(Token("-!"), wsp__), Series(Token("-&"), wsp__))
    factor = Alternative(Series(Option(flowmarker), Option(retrieveop), symbol,
eckhart's avatar
eckhart committed
196
197
198
199
                                NegativeLookahead(Series(Token("="), wsp__))), Series(Option(flowmarker), literal),
                         Series(Option(flowmarker), plaintext), Series(Option(flowmarker), regexp),
                         Series(Option(flowmarker), whitespace), Series(Option(flowmarker), oneormore),
                         Series(Option(flowmarker), group), Series(Option(flowmarker), unordered), repetition, option)
200
201
202
    term = OneOrMore(Series(Option(Series(Token("§"), wsp__)), factor))
    expression.set(Series(term, ZeroOrMore(Series(Series(Token("|"), wsp__), term))))
    directive = Series(Series(Token("@"), wsp__), symbol, Series(Token("="), wsp__),
eckhart's avatar
eckhart committed
203
204
                       Alternative(regexp, literal, symbol),
                       ZeroOrMore(Series(Series(Token(","), wsp__), Alternative(regexp, literal, symbol))), mandatory=1)
205
    definition = Series(symbol, Series(Token("="), wsp__), expression, mandatory=1)
eckhart's avatar
eckhart committed
206
    syntax = Series(Option(Series(wsp__, RegExp(''))), ZeroOrMore(Alternative(definition, directive)), EOF, mandatory=2)
di68kap's avatar
di68kap committed
207
208
209
    root__ = syntax


210
def grammar_changed(grammar_class, grammar_source: str) -> bool:
211
212
    """
    Returns ``True`` if ``grammar_class`` does not reflect the latest
Eckhart Arnold's avatar
Eckhart Arnold committed
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
    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()
eckhart's avatar
eckhart committed
231
        m = re.search(r'class \w*\(Grammar\)', pycode)
Eckhart Arnold's avatar
Eckhart Arnold committed
232
233
234
235
236
237
238
239
240
241
        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__


242
def get_ebnf_grammar() -> EBNFGrammar:
Eckhart Arnold's avatar
Eckhart Arnold committed
243
    try:
244
        grammar = GLOBALS.ebnf_grammar_singleton
Eckhart Arnold's avatar
Eckhart Arnold committed
245
        return grammar
246
    except AttributeError:
247
248
        GLOBALS.ebnf_grammar_singleton = EBNFGrammar()
        return GLOBALS.ebnf_grammar_singleton
Eckhart Arnold's avatar
Eckhart Arnold committed
249
250
251
252
253
254
255
256
257


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


258
EBNF_AST_transformation_table = {
259
    # AST Transformations for EBNF-grammar
260
    "<":
261
        [remove_empty],  # remove_whitespace
262
    "syntax":
263
        [],  # otherwise '"*": replace_by_single_child' would be applied
264
    "directive, definition":
eckhart's avatar
eckhart committed
265
        [flatten, remove_tokens('@', '=', ',')],
Eckhart Arnold's avatar
Eckhart Arnold committed
266
    "expression":
267
        [replace_by_single_child, flatten, remove_tokens('|')],  # remove_infix_operator],
268
    "term":
269
270
        [replace_by_single_child, flatten],  # supports both idioms:
                                             # "{ factor }+" and "factor { factor }"
271
    "factor, flowmarker, retrieveop":
272
        replace_by_single_child,
273
    "group":
274
        [remove_brackets, replace_by_single_child],
275
276
    "unordered":
        remove_brackets,
277
    "oneormore, repetition, option":
Eckhart Arnold's avatar
Eckhart Arnold committed
278
        [reduce_single_child, remove_brackets,
279
         forbid('repetition', 'option', 'oneormore'), assert_content(r'(?!§)(?:.|\n)*')],
280
    "symbol, literal, regexp":
Eckhart Arnold's avatar
Eckhart Arnold committed
281
        reduce_single_child,
282
    (TOKEN_PTYPE, WHITESPACE_PTYPE):
Eckhart Arnold's avatar
Eckhart Arnold committed
283
        reduce_single_child,
284
    "*":
285
        replace_by_single_child
286
287
}

288

Eckhart Arnold's avatar
Eckhart Arnold committed
289
def EBNFTransform() -> TransformationFunc:
290
    return partial(traverse, processing_table=EBNF_AST_transformation_table.copy())
di68kap's avatar
di68kap committed
291

eckhart's avatar
eckhart committed
292

293
def get_ebnf_transformer() -> TransformationFunc:
294
    try:
295
        transformer = GLOBALS.EBNF_transformer_singleton
296
    except AttributeError:
297
298
        GLOBALS.EBNF_transformer_singleton = EBNFTransform()
        transformer = GLOBALS.EBNF_transformer_singleton
299
    return transformer
Eckhart Arnold's avatar
Eckhart Arnold committed
300
301
302
303
304
305
306
307


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

308

309
PreprocessorFactoryFunc = Callable[[], PreprocessorFunc]
310
ParserFactoryFunc = Callable[[], Grammar]
311
TransformerFactoryFunc = Callable[[], TransformationFunc]
312
313
CompilerFactoryFunc = Callable[[], Compiler]

314
315
316
PREPROCESSOR_FACTORY = '''
def get_preprocessor() -> PreprocessorFunc:
    return {NAME}Preprocessor
317
318
319
320
'''


GRAMMAR_FACTORY = '''
321
def get_grammar() -> {NAME}Grammar:
322
    """Returns a thread/process-exclusive {NAME}Grammar-singleton."""
323
    try:
324
        grammar = GLOBALS.{NAME}_{ID:08d}_grammar_singleton
325
    except AttributeError:
326
        GLOBALS.{NAME}_{ID:08d}_grammar_singleton = {NAME}Grammar()
eckhart's avatar
eckhart committed
327
        if hasattr(get_grammar, 'python_src__'):
328
329
            GLOBALS.{NAME}_{ID:08d}_grammar_singleton.python_src__ = get_grammar.python_src__
        grammar = GLOBALS.{NAME}_{ID:08d}_grammar_singleton
330
    return grammar
331
332
333
334
'''


TRANSFORMER_FACTORY = '''
335
336
337
def Create{NAME}Transformer() -> TransformationFunc:
    """Creates a transformation function that does not share state with other
    threads or processes."""
338
339
    return partial(traverse, processing_table={NAME}_AST_transformation_table.copy())

340
def get_transformer() -> TransformationFunc:
341
    """Returns a thread/process-exclusive transformation function."""
342
    try:
343
        transformer = GLOBALS.{NAME}_{ID:08d}_transformer_singleton
344
    except AttributeError:
345
        GLOBALS.{NAME}_{ID:08d}_transformer_singleton = Create{NAME}Transformer()
346
        transformer = GLOBALS.{NAME}_{ID:08d}_transformer_singleton
347
    return transformer
348
349
350
351
'''


COMPILER_FACTORY = '''
eckhart's avatar
eckhart committed
352
def get_compiler() -> {NAME}Compiler:
353
    """Returns a thread/process-exclusive {NAME}Compiler-singleton."""
354
    try:
355
        compiler = GLOBALS.{NAME}_{ID:08d}_compiler_singleton
356
    except AttributeError:
357
358
        GLOBALS.{NAME}_{ID:08d}_compiler_singleton = {NAME}Compiler()
        compiler = GLOBALS.{NAME}_{ID:08d}_compiler_singleton
359
    return compiler
360
361
'''

Eckhart Arnold's avatar
Eckhart Arnold committed
362

363
364
365
366
WHITESPACE_TYPES = {'horizontal': r'[\t ]*',  # default: horizontal
                    'linefeed': r'[ \t]*\n?(?!\s*\n)[ \t]*',
                    'vertical': r'\s*'}

367
368
369
DROP_TOKEN  = 'token'
DROP_WSPC   = 'whitespace'
DROP_VALUES = {DROP_TOKEN, DROP_WSPC}
370

eckhart's avatar
eckhart committed
371
372
# Representation of Python code or, rather, something that will be output as Python code
ReprType = Union[str, unrepr]
eckhart's avatar
eckhart committed
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
class EBNFDirectives:
    """
    A Record that keeps information about compiler directives
    during the compilation process.

    Attributes:
        whitespace:  the regular expression string for (insignificant)
                whitespace

        comment:  the regular expression string for comments

        literalws:  automatic whitespace eating next to literals. Can
                be either 'left', 'right', 'none', 'both'

        tokens:  set of the names of preprocessor tokens
        filter:  mapping of symbols to python filter functions that
                will be called on any retrieve / pop - operations on
                these symbols

        error:  mapping of symbols to tuples of match conditions and
                customized error messages. A match condition can be
                either a string or a regular expression. The first
                error message where the search condition matches will
                be displayed. An empty string '' as search condition
                always matches, so in case of multiple error messages,
                this condition should be placed at the end.

402
403
404
405
406
407
408
409
410
411
412
413
        skip:  mapping of symbols to a list of search expressions. A
                search expressions can be either a string ot a regular
                expression. The closest match is the point of reentry
                for the series-parser when a mandatory item failed to
                match the following text.

        resume:  mapping of symbols to a list of search expressions. A
                search expressions can be either a string ot a regular
                expression. The closest match is the point of reentry
                for after a parsing error has error occurred. Other
                than the skip field, this configures resuming after
                the failing parser has returned.
414
    """
415
    __slots__ = ['whitespace', 'comment', 'literalws', 'tokens', 'filter', 'error', 'skip',
416
                 'resume', 'drop']
eckhart's avatar
eckhart committed
417

418
419
420
421
    def __init__(self):
        self.whitespace = WHITESPACE_TYPES['vertical']  # type: str
        self.comment = ''     # type: str
        self.literalws = {'right'}  # type: Collection[str]
eckhart's avatar
eckhart committed
422
        self.tokens = set()   # type: Collection[str]
423
        self.filter = dict()  # type: Dict[str, str]
eckhart's avatar
eckhart committed
424
        self.error = dict()   # type: Dict[str, List[Tuple[ReprType, ReprType]]]
425
        self.skip = dict()    # type: Dict[str, List[Union[unrepr, str]]]
426
        self.resume = dict()  # type: Dict[str, List[Union[unrepr, str]]]
427
        self.drop = set()     # type: Set[str]
428
429
430
431
432
433
434
435
436
437
438
439

    def __getitem__(self, key):
        return getattr(self, key)

    def __setitem__(self, key, value):
        assert hasattr(self, key)
        setattr(self, key, value)

    def keys(self):
        return self.__dict__.keys()


eckhart's avatar
eckhart committed
440
class EBNFCompilerError(CompilerError):
441
    """Error raised by `EBNFCompiler` class. (Not compilation errors
442
    in the strict sense, see `CompilationError` in module ``dsl.py``)"""
443
444
445
    pass


446
class EBNFCompiler(Compiler):
447
448
    """
    Generates a Parser from an abstract syntax tree of a grammar specified
449
    in EBNF-Notation.
450
451
452
453
454
455
456

    Instances of this class must be called with the root-node of the
    abstract syntax tree from an EBNF-specification of a formal language.
    The returned value is the Python-source-code of a Grammar class for
    this language that can be used to parse texts in this language.
    See classes `parser.Compiler` and `parser.Grammar` for more information.

457
    Additionally, class EBNFCompiler provides helper methods to generate
458
459
460
461
462
    code-skeletons for a preprocessor, AST-transformation and full
    compilation of the formal language. These method's names start with
    the prefix `gen_`.

    Attributes:
463
        current_symbols:  During compilation, a list containing the root
464
465
466
467
                node of the currently compiled definition as first element
                and then the nodes of the symbols that are referred to in
                the currently compiled definition.

468
        rules:  Dictionary that maps rule names to a list of Nodes that
469
470
471
472
473
474
                contain symbol-references in the definition of the rule.
                The first item in the list is the node of the rule-
                definition itself. Example:

                           `alternative = a | b`

475
                Now `[node.content for node in self.rules['alternative']]`
476
477
                yields `['alternative = a | b', 'a', 'b']`

478
        symbols:  A mapping of symbol names to their first usage (not
479
480
                their definition!) in the EBNF source.

481
        variables:  A set of symbols names that are used with the
482
483
484
485
                Pop or Retrieve operator. Because the values of these
                symbols need to be captured they are called variables.
                See `test_parser.TestPopRetrieve` for an example.

486
        recursive:  A set of symbols that are used recursively and
487
488
                therefore require a `Forward`-operator.

489
        definitions:  A dictionary of definitions. Other than `rules`
490
491
                this maps the symbols to their compiled definienda.

492
        deferred_tasks:  A list of callables that is filled during
493
494
495
496
497
                compilatation, but that will be executed only after
                compilation has finished. Typically, it contains
                sementatic checks that require information that
                is only available upon completion of compilation.

498
        root_symbol: The name of the root symbol.
499

500
501
502
503
504
505
506
507
508
509
510
511
        directives:  A record of all directives and their default values.

        defined_directives:  A set of all directives that have already been
                defined. With the exception of those directives contained
                in EBNFCompiler.REPEATABLE_DIRECTIVES, directives must only
                be defined once.

        consumed_custom_errors:  A set of symbols for which a custom error
                has been defined and(!) consumed during compilation. This
                allows to add a compiler error in those cases where (i) an
                error message has been defined but will never used or (ii)
                an error message is accidently used twice. For examples, see
512
513
514
515
                `test_ebnf.TestErrorCustomization`.

        consumed_skip_rules: The same as `consumed_custom_errors` only for
                in-series-resume-rules (aka 'skip-rules') for Series-parsers.
516
517
518

        re_flags:  A set of regular expression flags to be added to all
                regular expressions found in the current parsing process
519

eckhart's avatar
eckhart committed
520
521
522
523
        grammar_name:  The name of the grammar to be compiled

        grammar_source:  The source code of the grammar to be compiled.

524
525
526
        grammar_id: a unique id for every compiled grammar. (Required for
                disambiguation of of thread local variables storing
                compiled texts.)
527
528
    """
    COMMENT_KEYWORD = "COMMENT__"
529
    WHITESPACE_KEYWORD = "WSP_RE__"
Eckhart Arnold's avatar
Eckhart Arnold committed
530
    RAW_WS_KEYWORD = "WHITESPACE__"
531
    WHITESPACE_PARSER_KEYWORD = "wsp__"
532
    DROP_WHITESPACE_PARSER_KEYWORD = "dwsp__"
533
    RESUME_RULES_KEYWORD = "resume_rules__"
534
    SKIP_RULES_SUFFIX = '_skip__'
eckhart's avatar
eckhart committed
535
536
537
    ERR_MSG_SUFFIX = '_err_msg__'
    RESERVED_SYMBOLS = {WHITESPACE_KEYWORD, RAW_WS_KEYWORD, COMMENT_KEYWORD,
                        RESUME_RULES_KEYWORD, ERR_MSG_SUFFIX}
538
    AST_ERROR = "Badly structured syntax tree. " \
Eckhart Arnold's avatar
Eckhart Arnold committed
539
                "Potentially due to erroneous AST transformation."
540
541
542
543
    PREFIX_TABLE = {'§': 'Required',
                    '&': 'Lookahead', '!': 'NegativeLookahead',
                    '-&': 'Lookbehind', '-!': 'NegativeLookbehind',
                    '::': 'Pop', ':': 'Retrieve'}
544
    REPEATABLE_DIRECTIVES = {'tokens'}
545

546

eckhart's avatar
eckhart committed
547
    def __init__(self, grammar_name="DSL", grammar_source=""):
548
        self.grammar_id = 0
eckhart's avatar
eckhart committed
549
550
        super(EBNFCompiler, self).__init__()  # calls the _reset()-method
        self.set_grammar_name(grammar_name, grammar_source)
551

552

553
    def _reset(self):
554
        super(EBNFCompiler, self)._reset()
555
        self._result = ''           # type: str
556
        self.re_flags = set()       # type: Set[str]
557
558
559
        self.rules = OrderedDict()  # type: OrderedDict[str, List[Node]]
        self.current_symbols = []   # type: List[Node]
        self.symbols = {}           # type: Dict[str, Node]
560
561
        self.variables = set()      # type: Set[str]
        self.recursive = set()      # type: Set[str]
562
        self.definitions = {}       # type: Dict[str, str]
563
        self.deferred_tasks = []    # type: List[Callable]
564
        self.root_symbol = ""       # type: str
565
566
567
        self.directives = EBNFDirectives()   # type: EBNFDirectives
        self.defined_directives = set()      # type: Set[str]
        self.consumed_custom_errors = set()  # type: Set[str]
568
        self.consumed_skip_rules = set()     # type: Set[str]
569
570
        self.grammar_id += 1

571

Eckhart Arnold's avatar
Eckhart Arnold committed
572
    @property
573
    def result(self) -> str:
Eckhart Arnold's avatar
Eckhart Arnold committed
574
575
        return self._result

eckhart's avatar
eckhart committed
576
577
578
579
580
581
582
583
584
585
586
587

    def set_grammar_name(self, grammar_name: str = "", grammar_source: str = ""):
        """
        Changes the grammar name and source.

        The grammar name and the source text are metadata that do not affect the
        compilation process. It is used to name and annotate the output.
        Returns `self`.
        """
        assert grammar_name == "" or re.match(r'\w+\Z', grammar_name)
        if not grammar_name and re.fullmatch(r'[\w/:\\]+', grammar_source):
            grammar_name = os.path.splitext(os.path.basename(grammar_source))[0]
Eckhart Arnold's avatar
Eckhart Arnold committed
588
        self.grammar_name = grammar_name or "NameUnknown"
eckhart's avatar
eckhart committed
589
590
591
592
        self.grammar_source = load_if_file(grammar_source)
        return self


593
    # methods for generating skeleton code for preprocessor, transformer, and compiler
594

595
    def gen_preprocessor_skeleton(self) -> str:
596
597
598
599
        """
        Returns Python-skeleton-code for a preprocessor-function for
        the previously compiled formal language.
        """
600
        name = self.grammar_name + "Preprocessor"
601
        return "def %s(text):\n    return text, lambda i: i\n" % name \
602
               + PREPROCESSOR_FACTORY.format(NAME=self.grammar_name)
603

604

605
    def gen_transformer_skeleton(self) -> str:
606
607
608
609
        """
        Returns Python-skeleton-code for the AST-transformation for the
        previously compiled formal language.
        """
610
        if not self.rules:
Eckhart Arnold's avatar
Eckhart Arnold committed
611
612
            raise EBNFCompilerError('Compiler must be run before calling '
                                    '"gen_transformer_Skeleton()"!')
613
        tt_name = self.grammar_name + '_AST_transformation_table'
di68kap's avatar
di68kap committed
614
        transtable = [tt_name + ' = {',
Eckhart Arnold's avatar
Eckhart Arnold committed
615
                      '    # AST Transformations for the ' + self.grammar_name + '-grammar']
Eckhart Arnold's avatar
Eckhart Arnold committed
616
        transtable.append('    "<": flatten,')
617
        for name in self.rules:
eckhart's avatar
eckhart committed
618
            transformations = '[]'
619
620
621
622
623
            # rule = self.definitions[name]
            # if rule.startswith('Alternative'):
            #     transformations = '[replace_or_reduce]'
            # elif rule.startswith('Synonym'):
            #     transformations = '[reduce_single_child]'
eckhart's avatar
eckhart committed
624
            transtable.append('    "' + name + '": %s,' % transformations)
625
        # transtable.append('    ":Token": reduce_single_child,')
eckhart's avatar
eckhart committed
626
        transtable += ['    "*": replace_by_single_child', '}', '']
627
        transtable += [TRANSFORMER_FACTORY.format(NAME=self.grammar_name, ID=self.grammar_id)]
628
629
        return '\n'.join(transtable)

630

631
    def gen_compiler_skeleton(self) -> str:
632
633
634
635
        """
        Returns Python-skeleton-code for a Compiler-class for the
        previously compiled formal language.
        """
636
        if not self.rules:
637
638
            raise EBNFCompilerError('Compiler has not been run before calling '
                                    '"gen_Compiler_Skeleton()"!')
639
        compiler = ['class ' + self.grammar_name + 'Compiler(Compiler):',
eckhart's avatar
eckhart committed
640
641
                    '    """Compiler for the abstract-syntax-tree of a '
                    + self.grammar_name + ' source file.',
642
                    '    """', '',
eckhart's avatar
eckhart committed
643
644
645
                    '    def __init__(self):',
                    '        super(' + self.grammar_name + 'Compiler, self).__init__()',
                    '',
646
647
                    '    def _reset(self):',
                    '        super()._reset()',
eckhart's avatar
eckhart committed
648
649
                    '        # initialize your variables here, not in the constructor!',
                    '']
650
        for name in self.rules:
eckhart's avatar
eckhart committed
651
            method_name = visitor_name(name)
652
            if name == self.root_symbol:
653
                compiler += ['    def ' + method_name + '(self, node):',
654
                             '        return self.fallback_compiler(node)', '']
655
            else:
di68kap's avatar
di68kap committed
656
                compiler += ['    # def ' + method_name + '(self, node):',
eckhart's avatar
eckhart committed
657
                             '    #     return node', '']
658
        compiler += [COMPILER_FACTORY.format(NAME=self.grammar_name, ID=self.grammar_id)]
659
        return '\n'.join(compiler)
660

661
    def verify_transformation_table(self, transtable):
662
663
664
665
666
667
        """
        Checks for symbols that occur in the transformation-table but have
        never been defined in the grammar. Usually, this kind of
        inconsistency results from an error like a typo in the transformation
        table.
        """
668
        assert self._dirty_flag
669
        table_entries = set(expand_table(transtable).keys()) - {'*', '<', '>', '~'}
670
671
672
673
674
675
        symbols = self.rules.keys()
        messages = []
        for entry in table_entries:
            if entry not in symbols and not entry.startswith(":"):
                messages.append(Error(('Symbol "%s" is not defined in grammar %s but appears in '
                                       'the transformation table!') % (entry, self.grammar_name),
676
                                      0, Error.UNDEFINED_SYMBOL_IN_TRANSTABLE_WARNING))
677
678
        return messages

679
680
681
682
683
684
685
    def verify_compiler(self, compiler):
        """
        Checks for on_XXXX()-methods that occur in the compiler, although XXXX
        has never been defined in the grammar. Usually, this kind of
        inconsistency results from an error like a typo in the compiler-code.
        """
        pass  # TODO: add verification code here
686

687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709

    def _check_rx(self, node: Node, rx: str) -> str:
        """
        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.
        """
        flags = self.re_flags | {'x'} if rx.find('\n') >= 0 else self.re_flags
        if flags:
            rx = "(?%s)%s" % ("".join(flags), rx)
        try:
            re.compile(rx)
        except Exception as re_error:
            self.tree.new_error(node, "malformed regular expression %s: %s" %
                                (repr(rx), str(re_error)))
        return rx


    def _extract_regex(self, node: Node) -> str:
        """Extracts regular expression string from regexp-Node."""
        value = node.content.strip("~")
        if value[0] + value[-1] in {'""', "''"}:
            value = escape_re(value[1:-1])
710
        elif value[0] + value[-1] == '//' and value != '//':
711
712
713
714
            value = self._check_rx(node, value[1:-1])
        return value


eckhart's avatar
eckhart committed
715
    def _gen_search_rule(self, nd: Node) -> ReprType:
716
717
718
        """Generates a search rule, which can be either a string for simple
        string search or a regular expression from the nodes content. Returns
        an empty string in case the node is neither regexp nor literal.
719
        """
720
        if nd.tag_name == 'regexp':
721
            return unrepr("re.compile(r'%s')" % self._extract_regex(nd))
722
        elif nd.tag_name == 'literal':
723
724
725
726
            s = nd.content.strip()
            return s.strip('"') if s[0] == '"' else s.strip("'")
        return ''

727
728
729
730
731
732
733
    def _gen_search_list(self, nodes: Sequence[Node]) -> List[Union[unrepr, str]]:
        search_list = []  # type: List[Union[unrepr, str]]
        for child in nodes:
            rule = self._gen_search_rule(child)
            search_list.append(rule if rule else unrepr(child.content.strip()))
        return search_list

734

735
736
737
738
739
    def assemble_parser(self, definitions: List[Tuple[str, str]], root_node: Node) -> str:
        """
        Creates the Python code for the parser after compilation of
        the EBNF-Grammar
        """
740
741
742
743
744
745
746
747
748
749

        # execute deferred tasks, for example semantic checks that cannot
        # be done before the symbol table is complete

        for task in self.deferred_tasks:
            task()

        # provide for capturing of symbols that are variables, i.e. the
        # value of will be retrieved at some point during the parsing process

750
751
752
        if self.variables:
            for i in range(len(definitions)):
                if definitions[i][0] in self.variables:
753
                    definitions[i] = (definitions[i][0], 'Capture(%s)' % definitions[i][1])
754

755
756
        # add special fields for Grammar class

757
758
759
        if DROP_WSPC in self.directives.drop:
            definitions.append((self.DROP_WHITESPACE_PARSER_KEYWORD,
                                'DropWhitespace(%s)' % self.WHITESPACE_KEYWORD))
760
761
762
        else:
            definitions.append((self.WHITESPACE_PARSER_KEYWORD,
                                'Whitespace(%s)' % self.WHITESPACE_KEYWORD))
763
        definitions.append((self.WHITESPACE_KEYWORD,
eckhart's avatar
eckhart committed
764
765
                            ("mixin_comment(whitespace=" + self.RAW_WS_KEYWORD
                             + ", comment=" + self.COMMENT_KEYWORD + ")")))
766
767
        definitions.append((self.RAW_WS_KEYWORD, "r'{}'".format(self.directives.whitespace)))
        definitions.append((self.COMMENT_KEYWORD, "r'{}'".format(self.directives.comment)))
768
769
770

        # prepare and add resume-rules

eckhart's avatar
eckhart committed
771
        resume_rules = dict()  # type: Dict[str, List[ReprType]]
772
        for symbol, raw_rules in self.directives.resume.items():
773
774
775
776
777
            refined_rules = []
            for rule in raw_rules:
                if isinstance(rule, unrepr) and rule.s.isidentifier():
                    try:
                        nd = self.rules[rule.s][0].children[1]
778
                        refined = self._gen_search_rule(nd)
779
780
781
782
783
784
785
786
787
788
789
                    except IndexError:
                        refined = ""
                    if refined:
                        refined_rules.append(refined)
                    else:
                        self.tree.new_error(nd, 'Symbol "%s" cannot be used in resume rule, since'
                                                ' it represents neither literal nor regexp!')
                else:
                    refined_rules.append(rule)
            resume_rules[symbol] = refined_rules
        definitions.append((self.RESUME_RULES_KEYWORD, repr(resume_rules)))
790

eckhart's avatar
eckhart committed
791
792
        # prepare and add customized error-messages

793
        for symbol, err_msgs in self.directives.error.items():
eckhart's avatar
eckhart committed
794
            custom_errors = []  # type: List[Tuple[ReprType, ReprType]]
eckhart's avatar
eckhart committed
795
796
797
798
799
800
801
802
803
804
            for search, message in err_msgs:
                if isinstance(search, unrepr) and search.s.isidentifier():
                    try:
                        nd = self.rules[search.s][0].children[1]
                        search = self._gen_search_rule(nd)
                    except IndexError:
                        search = ''
                custom_errors.append((search, message))
            definitions.append((symbol + self.ERR_MSG_SUFFIX, repr(custom_errors)))

805
806
807
808
809
810
        for symbol in self.directives.error.keys():
            if symbol not in self.consumed_custom_errors:
                def_node = self.rules[symbol][0]
                self.tree.new_error(
                    def_node, 'Customized error message for symbol "{}" will never be used, '
                    'because the mandatory marker "§" appears nowhere in its definiendum!'
811
812
813
814
815
                    .format(symbol), Error.UNUSED_ERROR_HANDLING_WARNING)

        # prepare and add skip-rules

        for symbol, skip in self.directives.skip.items():
Eckhart Arnold's avatar
Eckhart Arnold committed
816
            skip_rules = []  # type: List[ReprType]
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
            for search in skip:
                if isinstance(search, unrepr) and search.s.isidentifier():
                    try:
                        nd = self.rules[search.s][0].children[1]
                        search = self._gen_search_rule(nd)
                    except IndexError:
                        search = ''
                skip_rules.append(search)
            definitions.append((symbol + self.SKIP_RULES_SUFFIX, repr(skip_rules)))

        for symbol in self.directives.error.keys():
            if symbol not in self.consumed_skip_rules:
                def_node = self.rules[symbol][0]
                self.tree.new_error(
                    def_node, '"Skip-rules" for symbol "{}" will never be used, '
                    'because the mandatory marker "§" appears nowhere in its definiendum!'
                    .format(symbol), Error.UNUSED_ERROR_HANDLING_WARNING)
834

835
836
        # prepare parser class header and docstring and
        # add EBNF grammar to the doc string of the parser class
837

838
        article = 'an ' if self.grammar_name[0:1] in "AaEeIiOoUu" else 'a '  # what about 'hour', 'universe' etc.?
839
        show_source = get_config_value('add_grammar_source_to_parser_docstring')
eckhart's avatar
eckhart committed
840
841
842
843
        declarations = ['class ' + self.grammar_name
                        + 'Grammar(Grammar):',
                        'r"""Parser for ' + article + self.grammar_name
                        + ' source file'
844
                        + ('. Grammar:' if self.grammar_source and show_source else '.')]
eckhart's avatar
eckhart committed
845
        definitions.append(('parser_initialization__', '["upon instantiation"]'))
846
        definitions.append(('static_analysis_pending__', '[True]'))
847
        if self.grammar_source:
848
            definitions.append(('source_hash__',
849
                                '"%s"' % md5(self.grammar_source, __version__)))
850
            declarations.append('')
851
852
            if show_source:
                declarations += [line for line in self.grammar_source.split('\n')]
853
854
855
856
857
            while declarations[-1].strip() == '':
                declarations = declarations[:-1]
        declarations.append('"""')

        # turn definitions into declarations in reverse order
858

859
        self.root_symbol = definitions[0][0] if definitions else ""
860
861
862
863
864
865
866
867
        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]
868
869
870
871
872
873

        # check for symbols used but never defined

        defined_symbols = set(self.rules.keys()) | self.RESERVED_SYMBOLS
        for symbol in self.symbols:
            if symbol not in defined_symbols:
eckhart's avatar
eckhart committed
874
                self.tree.new_error(self.symbols[symbol],
eckhart's avatar
eckhart committed
875
                                    "Missing definition for symbol '%s'" % symbol)
876
                # root_node.error_flag = True
877
878
879

        # check for unconnected rules

Eckhart Arnold's avatar
Eckhart Arnold committed
880
881
882
        defined_symbols.difference_update(self.RESERVED_SYMBOLS)

        def remove_connections(symbol):
883
            """Recursively removes all symbols which appear in the
eckhart's avatar
eckhart committed
884
            definiens of a particular symbol."""
Eckhart Arnold's avatar
Eckhart Arnold committed
885
886
887
888
889
890
891
            if symbol in defined_symbols:
                defined_symbols.remove(symbol)
                for related in self.rules[symbol][1:]:
                    remove_connections(str(related))

        remove_connections(self.root_symbol)
        for leftover in defined_symbols:
eckhart's avatar
eckhart committed
892
893
894
            self.tree.new_error(self.rules[leftover][0],
                                ('Rule "%s" is not connected to parser root "%s" !') %
                                (leftover, self.root_symbol), Error.WARNING)
895

896
        # set root_symbol parser and assemble python grammar definition
897

898
899
        if self.root_symbol and 'root__' not in self.rules:
            declarations.append('root__ = ' + self.root_symbol)
900
        declarations.append('')
Eckhart Arnold's avatar
Eckhart Arnold committed
901
        self._result = '\n    '.join(declarations) \
902
                       + GRAMMAR_FACTORY.format(NAME=self.grammar_name, ID=self.grammar_id)
Eckhart Arnold's avatar
Eckhart Arnold committed
903
        return self._result
904

905
906
907

    ## compilation methods

908
    def on_syntax(self, node: Node) -> str:
909
        definitions = []  # type: List[Tuple[str, str]]
910
911

        # drop the wrapping sequence node
912
        if len(node.children) == 1 and node.children[0].is_anonymous():
913
            node = node.children[0]
914
915

        # compile definitions and directives and collect definitions
916
        for nd in node.children:
917
            if nd.tag_name == "definition":
918
                definitions.append(self.compile(nd))
919
            else:
920
                assert nd.tag_name == "directive", nd.as_sxpr()
921
                self.compile(nd)
922
            # node.error_flag = max(node.error_flag, nd.error_flag)
923
        self.definitions.update(definitions)
924

925
        grammar_python_src = self.assemble_parser(definitions, node)
926
927
928
929
930
931
932
933
934
935
936
937
938
939
        if get_config_value('static_analysis') == 'early':
            try:
                grammar_class = compile_python_object(DHPARSER_IMPORTS + grammar_python_src,
                                                      self.grammar_name)
                _ = grammar_class()
                grammar_python_src = grammar_python_src.replace(
                    'static_analysis_pending__ = [True]', 'static_analysis_pending__ = []', 1)
            except NameError:
                pass  # undefined name in the grammar are already caught and reported
            except GrammarError as error:
                for sym, prs, err in error.errors:
                    symdef_node = self.rules[sym][0]
                    err.pos = self.rules[sym][0].pos
                    self.tree.add_error(symdef_node, err)
940
        return grammar_python_src
941

942

943
    def on_definition(self, node: Node) -> Tuple[str, str]:
944
        rule = node.children[0].content
945
        if rule in self.rules:
Eckhart Arnold's avatar
Eckhart Arnold committed
946
            first = self.rules[rule][0]
947
            if not id(first) in self.tree.error_nodes:
eckhart's avatar
eckhart committed
948
                self.tree.new_error(first, 'First definition of rule "%s" '
eckhart's avatar
eckhart committed
949
                                    'followed by illegal redefinitions.' % rule)
eckhart's avatar
eckhart committed
950
            self.tree.new_error(node, 'A rule "%s" has already been defined earlier.' % rule)
951
        elif rule in EBNFCompiler.RESERVED_SYMBOLS:
eckhart's avatar
eckhart committed
952
            self.tree.new_error(node, 'Symbol "%s" is a reserved symbol.' % rule)
953
        elif not sane_parser_name(rule):
eckhart's avatar
eckhart committed
954
            self.tree.new_error(node, 'Illegal symbol "%s". Symbols must not start or '
eckhart's avatar
eckhart committed
955
                                ' end with a doube underscore "__".' % rule)
956
        elif rule in self.directives.tokens:
eckhart's avatar
eckhart committed
957
            self.tree.new_error(node, 'Symbol "%s" has already been defined as '
eckhart's avatar
eckhart committed
958
                                'a preprocessor token.' % rule)
959
        elif keyword.iskeyword(rule):
eckhart's avatar
eckhart committed
960
            self.tree.new_error(node, 'Python keyword "%s" may not be used as a symbol. '
eckhart's avatar
eckhart committed
961
                                % rule + '(This may change in the future.)')
962
        try:
963
964
            self.current_symbols = [node]
            self.rules[rule] = self.current_symbols
965
            defn = self.compile(node.children[1])
966
            if rule in self.variables:
967
                defn = 'Capture(%s)' % defn
968
                self.variables.remove(rule)
969
970
971
            elif defn.find("(") < 0:
                # assume it's a synonym, like 'page = REGEX_PAGE_NR'
                defn = 'Synonym(%s)' % defn
972
        except TypeError as error:
973
974