syntaxtree.py 22.3 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
"""syntaxtree.py - syntax tree classes and transformation functions for 
converting the concrete into the abstract syntax tree 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.
"""

20
import copy
21
import itertools
22
23
import os
from functools import partial
24
25
26
27
try:
    import regex as re
except ImportError:
    import re
28
29
from typing import NamedTuple

Eckhart Arnold's avatar
Eckhart Arnold committed
30
from .toolkit import is_logging, log_dir, expand_table, line_col, smart_list
31

Eckhart Arnold's avatar
Eckhart Arnold committed
32
33
34
35
36
37

__all__ = ['WHITESPACE_KEYWORD',
           'TOKEN_KEYWORD',
           'ZOMBIE_PARSER',
           'Error',
           'Node',
38
           'mock_syntax_tree',
39
           'traverse',
di68kap's avatar
di68kap committed
40
           'no_operation',
Eckhart Arnold's avatar
Eckhart Arnold committed
41
42
43
44
45
46
47
48
49
50
51
           'replace_by_single_child',
           'reduce_single_child',
           'is_whitespace',
           'is_empty',
           'is_expendable',
           'is_token',
           'remove_children_if',
           'remove_whitespace',
           'remove_expendables',
           'remove_tokens',
           'flatten',
52
53
54
55
           'remove_enclosing_delimiters',
           'forbid',
           'require',
           'assert_content']
Eckhart Arnold's avatar
Eckhart Arnold committed
56
57


58
class MockParser:
59
60
61
62
63
64
65
66
67
68
    """
    MockParser objects can be used to reconstruct syntax trees from a
    serialized form like S-expressions or XML. Mock objects are needed,
    because Node objects require a parser object for instantiation.
    Mock objects have just enough properties to serve that purpose. 
    
    Mock objects should not be used for anything other than 
    syntax tree (re-)construction. In all other cases where a parser
    object substitute is needed, chose the singleton ZOMBIE_PARSER.
    """
69
70
71
72
73
74
75
76
    def __init__(self, name=''):
        self.name = name

    def __str__(self):
        return self.name or self.__class__.__name__


class ZombieParser(MockParser):
77
78
79
80
81
82
83
84
85
86
87
88
    """
    Serves as a substitute for a Parser instance.

    ``ZombieParser`` is the class of the singelton object
    ``ZOMBIE_PARSER``. The  ``ZOMBIE_PARSER`` has a name and can be
    called, but it never matches. It serves as a substitute where only
    these (or one of these properties) is needed, but no real Parser-
    object is instantiated.
    """
    alive = False

    def __init__(self):
89
        super(ZombieParser, self).__init__("ZOMBIE")
90
91
92
93
        assert not self.__class__.alive, "There can be only one!"
        assert self.__class__ == ZombieParser, "No derivatives, please!"
        self.__class__.alive = True

Eckhart Arnold's avatar
Eckhart Arnold committed
94
95
96
97
98
99
    def __copy__(self):
        return self

    def __deepcopy__(self, memo):
        return self

100
101
102
103
    def __call__(self, text):
        """Better call Saul ;-)"""
        return None, text

104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

ZOMBIE_PARSER = ZombieParser()


class Error(NamedTuple):
    pos: int
    msg: str


class Node:
    """
    Represents a node in the concrete or abstract syntax tree.

    Attributes:
        tag_name (str):  The name of the node, which is either its
            parser's name or, if that is empty, the parser's class name
        result (str or tuple):  The result of the parser which
            generated this node, which can be either a string or a
            tuple of child nodes.
        children (tuple):  The tuple of child nodes or an empty tuple
            if there are no child nodes. READ ONLY!
        parser (Parser):  The parser which generated this node.
        errors (list):  A list of parser- or compiler-errors:
            tuple(position, string) attached to this node
        len (int):  The full length of the node's string result if the
            node is a leaf node or, otherwise, the concatenated string
            result's of its descendants. The figure always represents
            the length before AST-transformation ans will never change
            through AST-transformation. READ ONLY!
        pos (int):  the position of the node within the parsed text.

            The value of ``pos`` is -1 meaning invalid by default. 
            Setting this value will set the positions of all child
            nodes relative to this value.  

            To set the pos values of all nodes in a syntax tree, the
            pos value of the root node should be set to 0 right 
            after parsing.

            Other than that, this value should be considered READ ONLY. 
            At any rate, it should only be reassigned only during
            parsing stage and never during or after the
            AST-transformation.
    """

    def __init__(self, parser, result):
        """Initializes the ``Node``-object with the ``Parser``-Instance
        that generated the node and the parser's result.
        """
        self.result = result
        self.parser = parser or ZOMBIE_PARSER
        self._errors = []
        self.error_flag = any(r.error_flag for r in self.result) if self.children else False
        self._len = len(self.result) if not self.children else \
            sum(child._len for child in self.children)
        # self.pos = 0  # coninuous updating of pos values
        self._pos = -1

    def __str__(self):
        if self.children:
164
            return "".join(str(child) for child in self.result)
165
166
        return str(self.result)

167
168
169
    def __eq__(self, other):
        return str(self.parser) == str(other.parser) and self.result == other.result

170
171
172
173
174
175
176
177
178
    def __hash__(self):
        return hash((str(self.parser), ))

    def __deepcopy__(self, memodict={}):
        result = copy.deepcopy(self.result)
        other = Node(self.parser, result)
        other._pos = self._pos
        return other

179
180
    @property
    def tag_name(self):
181
        return self.parser.name or self.parser.__class__.__name__
182
        # ONLY FOR DEBUGGING: return self.parser.name + ':' + self.parser.__class__.__name__
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211

    @property
    def result(self):
        return self._result

    @result.setter
    def result(self, result):
        assert ((isinstance(result, tuple) and all(isinstance(child, Node) for child in result))
                or isinstance(result, Node)
                or isinstance(result, str)), str(result)
        self._result = (result,) if isinstance(result, Node) else result or ''
        self._children = self._result if isinstance(self._result, tuple) else ()

    @property
    def children(self):
        return self._children

    @property
    def len(self):
        # DEBUGGING:  print(str(self.parser), str(self.pos), str(self._len), str(self)[:10].replace('\n','.'))
        return self._len

    @property
    def pos(self):
        assert self._pos >= 0, "position value not initialized!"
        return self._pos

    @pos.setter
    def pos(self, pos):
212
        assert isinstance(pos, int)
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
        self._pos = pos
        offset = 0
        for child in self.children:
            child.pos = pos + offset
            offset += child.len

    @property
    def errors(self):
        return [Error(self.pos, err) for err in self._errors]

    def _tree_repr(self, tab, openF, closeF, dataF=lambda s: s):
        """
        Generates a tree representation of this node and its children
        in string from.

        The kind ot tree-representation that is determined by several
        function parameters. This could be an XML-representation or a
        lisp-like S-expression.

232
        Args:
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
            tab (str):  The indentation string, e.g. '\t' or '    '
            openF:  (Node->str) A function that returns an opening
                string (e.g. an XML-tag_name) for a given node
            closeF:  (Node->str) A function that returns a closeF
                string (e.g. an XML-tag_name) for a given node.
            dataF:  (str->str) A function that filters the data string
                before printing, e.g. to add quotation marks

        Returns (str):
            A string that contains a (serialized) tree representation
            of the node and its children.
        """
        head = openF(self)
        tail = closeF(self)

        if not self.result:
            return head + tail

        head = head + '\n'  # place the head, tail and content
        tail = '\n' + tail  # of the node on different lines

        if self.children:
            content = []
            for child in self.result:
                subtree = child._tree_repr(tab, openF, closeF, dataF).split('\n')
                content.append('\n'.join((tab + s) for s in subtree))
            return head + '\n'.join(content) + tail

        return head + '\n'.join([tab + dataF(s)
                                 for s in str(self.result).split('\n')]) + tail

264
    def as_sexpr(self, src=None):
265
266
267
        """
        Returns content as S-expression, i.e. in lisp-like form.

268
        Args:
269
270
271
            src:  The source text or `None`. In case the source text is
                given the position of the element in the text will be
                reported as line and column.
272
273
            prettyprint(bool):  True (default), if pretty printing 
                of leaf nodes shall be applied for better readability.
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
        """

        def opening(node):
            s = '(' + node.tag_name
            # s += " '(pos %i)" % node.pos
            if src:
                s += " '(pos %i  %i %i)" % (node.pos, *line_col(src, node.pos))
            if node.errors:
                s += " '(err '(%s))" % ' '.join(str(err).replace('"', r'\"')
                                                for err in node.errors)
            return s

        def pretty(s):
            return '"%s"' % s if s.find('"') < 0 \
                else "'%s'" % s if s.find("'") < 0 \
                else '"%s"' % s.replace('"', r'\"')

291
        return self._tree_repr('    ', opening, lambda node: ')', pretty)  # pretty if prettyprint else lambda s: s)
292
293
294
295
296

    def as_xml(self, src=None):
        """
        Returns content as XML-tree.

297
        Args:
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
            src:  The source text or `None`. In case the source text is
                given the position will also be reported as line and
                column.
        """

        def opening(node):
            s = '<' + node.tag_name
            # s += ' pos="%i"' % node.pos
            if src:
                s += ' line="%i" col="%i"' % line_col(src, node.pos)
            if node.errors:
                s += ' err="%s"' % ''.join(str(err).replace('"', r'\"') for err in node.errors)
            s += ">"
            return s

        def closing(node):
            s = '</' + node.tag_name + '>'
            return s

        return self._tree_repr('    ', opening, closing)

    def add_error(self, error_str):
        self._errors.append(error_str)
        self.error_flag = True
        return self

    def collect_errors(self, clear_errors=False):
        """
        Returns all errors of this node or any child node in the form
        of a set of tuples (position, error_message), where position
        is always relative to this node.
        """
330
        errors = []
331
332
333
334
335
336
337
338
        if self.error_flag:
            errors = self.errors
            if clear_errors:
                self._errors = []
                self.error_flag = False
            if self.children:
                for child in self.result:
                    errors.extend(child.collect_errors(clear_errors))
339
        return errors
340
341

    def log(self, log_file_name, ext):
Eckhart Arnold's avatar
Eckhart Arnold committed
342
        if is_logging():
343
            st_file_name = log_file_name + ext
Eckhart Arnold's avatar
Eckhart Arnold committed
344
            with open(os.path.join(log_dir(), st_file_name), "w", encoding="utf-8") as f:
345
346
                f.write(self.as_sexpr())

347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
    def find(self, match_function):
        """Finds nodes in the tree that match a specific criterion.
        
        ``find`` is a generator that yields all nodes for which the
        given ``match_function`` evaluates to True. The tree is 
        traversed pre-order.
        
        Args:
            match_function (function): A function  that takes as Node
                object as argument and returns True or False
        Yields:
            Node: all nodes of the tree for which 
            ``match_function(node)`` returns True
        """
        if match_function(self):
            yield self
        else:
            for child in self.children:
                for nd in child.find(match_function):
                    yield nd

368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
    # def range(self, match_first, match_last):
    #     """Iterates over the range of nodes, starting from the first
    #     node for which ``match_first`` becomes True until the first node
    #     after this one for which ``match_last`` becomes true or until
    #     the end if it never does.
    #
    #     Args:
    #         match_first (function): A function  that takes as Node
    #             object as argument and returns True or False
    #         match_last (function): A function  that takes as Node
    #             object as argument and returns True or False
    #     Yields:
    #         Node: all nodes of the tree for which
    #         ``match_function(node)`` returns True
    #     """


385
    def navigate(self, path):
386
387
388
389
390
        """Yields the results of all descendant elements matched by
        ``path``, e.g.
        'd/s' yields 'l' from (d (s l)(e (r x1) (r x2))
        'e/r' yields 'x1', then 'x2'
        'e'   yields (r x1)(r x2)
391

392
        Args:
393
394
            path (str):  The path of the object, e.g. 'a/b/c'. The
                components of ``path`` can be regular expressions
395
396
397
398
399

        Returns:
            The object at the path, either a string or a Node or
            ``None``, if the path did not match.
        """
400
401
402
403
        def nav(node, pl):
            if pl:
                return itertools.chain(nav(child, pl[1:]) for child in node.children
                                       if re.match(pl[0], child.tag_name))
404
            else:
405
406
                return self.result,
        return nav(path.split('/'))
407
408


409
410
411
412
413
414
415
def mock_syntax_tree(sexpr):
    """Generates a tree of nodes from an S-expression.

    Example: 
    >>> mock_syntax_tree("(a (b c))").as_sexpr()
    (a 
        (b 
416
            "c" 
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
        )
    )
    """
    def next_block(s):
        s = s.strip()
        while s[0] != ')':
            assert s[0] == '(', s
            level = 1;
            i = 1
            while level > 0:
                if s[i] == '(':
                    level += 1
                elif s[i] == ')':
                    level -= 1
                i += 1
            yield s[:i]
            s = s[i:].strip()

    sexpr = sexpr.strip()
    assert sexpr[0] == '(', sexpr
    sexpr = sexpr[1:].strip()
    m = re.match('\w+', sexpr)
    name = sexpr[:m.end()]
    sexpr = sexpr[m.end():].strip()
    if sexpr[0] == '(':
        result = tuple(mock_syntax_tree(block) for block in next_block(sexpr))
    else:
444
445
446
447
448
449
450
451
452
453
454
455
456
457
        lines = []
        while sexpr and sexpr[0] != ')':
            for qm in ['"""', "'''", '"', "'"]:
                m = re.match(qm + r'.*?' + qm, sexpr)
                if m:
                    i = len(qm)
                    lines.append(sexpr[i:m.end() - i])
                    sexpr = sexpr[m.end():].strip()
                    break
            else:
                m = re.match(r'(?:(?!\)).)*', sexpr)
                lines.append(sexpr[:m.end()])
                sexpr = sexpr[m.end():]
        result = "\n".join(lines)
458
459
460
    return Node(MockParser(name), result)


461
462
463
464
465
466
467
########################################################################
#
# syntax tree transformation functions
#
########################################################################


468
469
470
471
WHITESPACE_KEYWORD = 'WSP__'
TOKEN_KEYWORD = 'TOKEN__'


di68kap's avatar
di68kap committed
472
def traverse(root_node, processing_table):
473
474
475
476
477
478
479
480
    """Traverses the snytax tree starting with the given ``node`` depth
    first and applies the sequences of callback functions registered
    in the ``calltable``-dictionary.
    
    Possible use cases are the transformation of a concrete syntax tree
    into an abstract tree (AST) or the semantic analysis of the AST.
    
    Args:
di68kap's avatar
di68kap committed
481
482
483
484
        root_node (Node): The root-node of the syntax tree to be traversed 
        processing_table (dict): parser.name -> sequence of functions that
            will be applied to matching nodes in order. This dictionary
            is interpreted as a ``compact_table``. See 
485
486
487
488
489
490
            ``toolkit.expand_table`` or ``EBNFCompiler.EBNFTransTable``
            
    Example:
        table = { "term": [replace_by_single_child, flatten], 
            "factor, flowmarker, retrieveop": replace_by_single_child }
        traverse(node, table)
491
    """
di68kap's avatar
di68kap committed
492
    # normalize processing_table entries by turning single values into lists
493
    # with a single value
494
    table = {name: smart_list(call) for name, call in list(processing_table.items())}
495
496
    table = expand_table(table)

di68kap's avatar
di68kap committed
497
498
499
    def traverse_recursive(node):
        if node.children:
            for child in node.result:
500
                traverse_recursive(child)
501
                node.error_flag |= child.error_flag  # propagate error flag
502
503
504
505
506
507
        sequence = table.get('*', []) + \
                   table.get(node.parser.name, table.get('?', [])) + \
                   table.get('~', [])
        # '*' always called (before any other processing function)
        # '?' called for those nodes for which no (other) processing functions is in the table
        # '~' always called (after any other processing function)
508
        for call in sequence:
di68kap's avatar
di68kap committed
509
            call(node)
510

di68kap's avatar
di68kap committed
511
    traverse_recursive(root_node)
512
513


di68kap's avatar
di68kap committed
514
def no_operation(node):
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
    pass


# ------------------------------------------------
#
# rearranging transformations:
#     - tree may be rearranged (flattened)
#     - order is preserved
#     - all leaves are kept
#
# ------------------------------------------------


def replace_by_single_child(node):
    """Remove single branch node, replacing it by its immediate descendant.
    (In case the descendant's name is empty (i.e. anonymous) the
    name of this node's parser is kept.)
    """
    if node.children and len(node.result) == 1:
        if not node.result[0].parser.name:
            node.result[0].parser.name = node.parser.name
        node.parser = node.result[0].parser
        node._errors.extend(node.result[0].errors)
        node.result = node.result[0].result


def reduce_single_child(node):
    """Reduce a single branch node, by transferring the result of its
    immediate descendant to this node, but keeping this node's parser entry.
    """
    if node.children and len(node.result) == 1:
        node._errors.extend(node.result[0].errors)
        node.result = node.result[0].result


# ------------------------------------------------
#
# destructive transformations:
#     - tree may be rearranged (flattened),
#     - order is preserved
#     - but (irrelevant) leaves may be dropped
#     - errors of dropped leaves will be lost
#
# ------------------------------------------------


def is_whitespace(node):
    """Removes whitespace and comments defined with the
    ``@comment``-directive."""
    return node.parser.name == WHITESPACE_KEYWORD


# def is_scanner_token(node):
#     return isinstance(node.parser, ScannerToken)


def is_empty(node):
    return not node.result


def is_expendable(node):
    return is_empty(node) or is_whitespace(node)  # or is_scanner_token(node)


Eckhart Arnold's avatar
Eckhart Arnold committed
579
def is_token(node, token_set=frozenset()):
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
    return node.parser.name == TOKEN_KEYWORD and (not token_set or node.result in token_set)


def remove_children_if(node, condition):
    """Removes all nodes from the result field if the function 
    ``condition(child_node)`` evaluates to ``True``."""
    if node.children:
        node.result = tuple(c for c in node.children if not condition(c))


remove_whitespace = partial(remove_children_if, condition=is_whitespace)
# remove_scanner_tokens = partial(remove_children_if, condition=is_scanner_token)
remove_expendables = partial(remove_children_if, condition=is_expendable)


Eckhart Arnold's avatar
Eckhart Arnold committed
595
def remove_tokens(node, tokens=frozenset()):
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
    """Reomoves any among a particular set of tokens from the immediate
    descendants of a node. If ``tokens`` is the empty set, all tokens
    are removed.
    """
    remove_children_if(node, partial(is_token, token_set=tokens))


def flatten(node):
    """Recursively flattens all unnamed sub-nodes, in case there is more
    than one sub-node present. Flattening means that
    wherever a node has child nodes, the child nodes are inserted in place
    of the node. In other words, all leaves of this node and its child nodes
    are collected in-order as direct children of this node.
    This is meant to achieve these kinds of structural transformation:
        (1 (+ 2) (+ 3)     ->   (1 + 2 + 3)
        (1 (+ (2 + (3))))  ->   (1 + 2 + 3)

    Warning: Use with care. Du tue its recursive nature, flattening can
    have unexpected side-effects.
    """
    if node.children:
        new_result = []
        for child in node.children:
            if not child.parser.name and child.children:
                assert child.children, node.as_sexpr()
                flatten(child)
                new_result.extend(child.result)
            else:
                new_result.append(child)
        node.result = tuple(new_result)


628
def remove_enclosing_delimiters(node):
629
630
631
632
633
634
635
636
    """Removes any enclosing delimiters from a structure (e.g. quotation marks
    from a literal or braces from a group).
    """
    if len(node.children) >= 3:
        assert not node.children[0].children and not node.children[-1].children, node.as_sexpr()
        node.result = node.result[1:-1]


637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
########################################################################
#
# syntax tree validation functions
#
########################################################################


def require(node, child_tags):
    for child in node.children:
        if child.tag_name not in child_tags:
            node.add_error('Element "%s" is not allowed inside "%s".' %
                           (child.tag_name, node.tag_name))


def forbid(node, child_tags):
    for child in node.children:
        if child.tag_name in child_tags:
            node.add_error('Element "%s" cannot be nested inside "%s".' %
                           (child.tag_name, node.tag_name))


def assert_content(node, regex):
    content = str(node)
    if not re.match(regex, content):
        node.add_error('Element "%s" violates %s on %s' %
                       (node.tag_name, str(regex), content))