transform.py 40.6 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
# transform.py - transformation functions for converting the
#                concrete into the abstract syntax tree
#
# 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.
18
19


20
21
22
"""
Module ``transform`` contains the functions for transforming the
concrete syntax tree (CST) into an abstract syntax tree (AST).
23

24
25
26
As these functions are very generic, they can in principle be
used for any kind of tree transformations, not necessarily only
for CST -> AST transformations.
27
28
"""

29

30
import collections.abc
31
import inspect
eckhart's avatar
eckhart committed
32
from functools import partial, singledispatch
33

34
from DHParser.error import Error, ErrorCode
35
from DHParser.syntaxtree import Node, WHITESPACE_PTYPE, TOKEN_PTYPE, PLACEHOLDER, RootNode, parse_sxpr, flatten_sxpr
36
from DHParser.toolkit import issubtype, isgenerictype, expand_table, smart_list, re, typing
37
from typing import AbstractSet, Any, ByteString, Callable, cast, Container, Dict, \
38
    Tuple, List, Sequence, Union, Text, Generic
39

40
41
__all__ = ('TransformationDict',
           'TransformationProc',
42
           'TransformationFunc',
43
44
45
           'ConditionFunc',
           'KeyFunc',
           'transformation_factory',
46
47
           'key_tag_name',
           'traverse',
48
           'is_named',
49
           'update_attr',
50
           'flatten_anonymous_nodes',
51
           'replace_by_single_child',
Eckhart Arnold's avatar
Eckhart Arnold committed
52
           'reduce_single_child',
53
           'replace_or_reduce',
54
55
           'replace_parser',
           'collapse',
56
           'collapse_if',
57
           # 'merge_children',
58
           'replace_content',
59
           'replace_content_by',
60
           'normalize_whitespace',
61
           'move_adjacent',
62
           'apply_if',
eckhart's avatar
eckhart committed
63
           'apply_unless',
64
           'traverse_locally',
65
           'is_anonymous',
66
67
68
           'is_insignificant_whitespace',
           'contains_only_whitespace',
           'is_any_kind_of_whitespace',
69
70
71
           'is_empty',
           'is_expendable',
           'is_token',
72
           'is_one_of',
73
           'not_one_of',
Eckhart Arnold's avatar
Eckhart Arnold committed
74
           'matches_re',
75
           'has_content',
di68kap's avatar
di68kap committed
76
           'has_parent',
77
78
79
80
81
82
83
84
           'lstrip',
           'rstrip',
           'strip',
           'keep_children',
           'keep_children_if',
           'keep_tokens',
           'keep_nodes',
           'keep_content',
85
           'remove_children_if',
eckhart's avatar
eckhart committed
86
           'remove_nodes',
87
88
89
90
91
           'remove_content',
           'remove_first',
           'remove_last',
           'remove_whitespace',
           'remove_empty',
di68kap's avatar
di68kap committed
92
           'remove_anonymous_empty',
93
94
           'remove_anonymous_expendables',
           'remove_anonymous_tokens',
95
96
           'remove_expendables',
           'remove_brackets',
97
98
           'remove_infix_operator',
           'remove_single_child',
99
100
101
102
           'remove_tokens',
           'flatten',
           'forbid',
           'require',
103
           'assert_content',
104
           'error_on',
di68kap's avatar
di68kap committed
105
106
           'assert_has_children',
           'peek')
107
108


109
TransformationProc = Callable[[List[Node]], None]
Eckhart Arnold's avatar
Eckhart Arnold committed
110
TransformationDict = Dict[str, Sequence[Callable]]
111
TransformationFunc = Union[Callable[[Node], Any], partial]
Eckhart Arnold's avatar
Eckhart Arnold committed
112
ProcessingTableType = Dict[str, Union[Sequence[Callable], TransformationDict]]
113
114
ConditionFunc = Callable  # Callable[[List[Node]], bool]
KeyFunc = Callable[[Node], str]
eckhart's avatar
eckhart committed
115
CriteriaType = Union[int, str, Callable]
116
117


118
def transformation_factory(t1=None, t2=None, t3=None, t4=None, t5=None):
119
120
    """
    Creates factory functions from transformation-functions that
121
    dispatch on the first parameter after the context parameter.
122
123

    Decorating a transformation-function that has more than merely the
Eckhart Arnold's avatar
Eckhart Arnold committed
124
    ``context``-parameter with ``transformation_factory`` creates a
125
    function with the same name, which returns a partial-function that
126
    takes just the context-parameter.
127
128
129
130
131
132
133
134
135

    Additionally, there is some some syntactic sugar for
    transformation-functions that receive a collection as their second
    parameter and do not have any further parameters. In this case a
    list of parameters passed to the factory function will be converted
    into a collection.

    Main benefit is readability of processing tables.

136
137
    Usage::

eckhart's avatar
eckhart committed
138
        @transformation_factory(AbstractSet[str])
139
        def remove_tokens(context, tokens):
140
            ...
141
142
143

    or, alternatively::

144
        @transformation_factory
145
        def remove_tokens(context, tokens: AbstractSet[str]):
146
147
            ...

148
149
    Example::

150
        trans_table = { 'expression': remove_tokens('+', '-') }
151
152
153

    instead of::

154
        trans_table = { 'expression': partial(remove_tokens, tokens={'+', '-'}) }
155
156

    Parameters:
157
        t1:  type of the second argument of the transformation function,
158
159
            only necessary if the transformation functions' parameter list
            does not have type annotations.
160
161
    """

162
163
164
165
    def type_guard(t):
        """Raises an error if type `t` is a generic type or could be mistaken
        for the type of the canonical first parameter "List[Node] of
        transformation functions. Returns `t`."""
166
167
168
169
        # if isinstance(t, GenericMeta):
        #     raise TypeError("Generic Type %s not permitted\n in transformation_factory "
        #                     "decorator. Use the equivalent non-generic type instead!"
        #                     % str(t))
Eckhart Arnold's avatar
Eckhart Arnold committed
170
171
        if isinstance(t, str):          # ensure compatibility with python versions
            t = eval(t.replace('unicode', 'str'))  # with alternative type handling.
172
        if isgenerictype(t):
173
174
175
            raise TypeError("Generic Type %s not permitted\n in transformation_factory "
                            "decorator. Use the equivalent non-generic type instead!"
                            % str(t))
176
        if issubtype(List[Node], t):
177
178
            raise TypeError("Sequence type %s not permitted\nin transformation_factory "
                            "decorator, because it could be mistaken for a base class "
179
180
181
                            "of List[Node]\nwhich is the type of the canonical first "
                            "argument of transformation functions. Try 'tuple' instead!"
                            % str(t))
182
183
        return t

184
    def decorator(f):
185
        nonlocal t1
186
187
188
189
        sig = inspect.signature(f)
        params = list(sig.parameters.values())[1:]
        if len(params) == 0:
            return f  # '@transformer' not needed w/o free parameters
190
        assert t1 or params[0].annotation != params[0].empty, \
191
            "No type information on second parameter found! Please, use type " \
eckhart's avatar
eckhart committed
192
            "annotation or provide the type information via transformer-decorator."
193
        f = singledispatch(f)
194
195
196
        p1type = params[0].annotation
        if t1 is None:
            t1 = type_guard(p1type)
197
        elif issubtype(p1type, type_guard(t1)):
198
            try:
199
                if len(params) == 1 and issubtype(p1type, Container) \
200
                        and not (issubtype(p1type, Text) or issubtype(p1type, ByteString)):
201
                    def gen_special(*args):
202
203
                        c = set(args) if issubtype(p1type, AbstractSet) else \
                            tuple(args) if issubtype(p1type, Sequence) else args
204
205
206
207
208
209
210
211
                        d = {params[0].name: c}
                        return partial(f, **d)
                    f.register(type_guard(p1type.__args__[0]), gen_special)
            except AttributeError:
                pass  # Union Type does not allow subclassing, but is not needed here
        else:
            raise TypeError("Annotated type %s is not a subclass of decorated type %s !"
                            % (str(p1type), str(t1)))
212
213
214
215
216
217

        def gen_partial(*args, **kwargs):
            d = {p.name: arg for p, arg in zip(params, args)}
            d.update(kwargs)
            return partial(f, **d)

218
        for t in (t1, t2, t3, t4, t5):
219
            if t:
220
                f.register(type_guard(t), gen_partial)
221
222
            else:
                break
223
224
        return f

225
    if isinstance(t1, type(lambda: 1)):
226
227
228
        # Provide for the case that transformation_factory has been
        # written as plain decorator and not as a function call that
        # returns the decorator proper.
229
230
        func = t1
        t1 = None
231
232
233
234
235
        return decorator(func)
    else:
        return decorator


236
237
# def key_parser_name(node: Node) -> str:
#     return node.parser.name
238
239


240
def key_tag_name(node: Node) -> str:
241
242
243
    return node.tag_name


244
def traverse(root_node: Node,
Eckhart Arnold's avatar
Eckhart Arnold committed
245
             processing_table: ProcessingTableType,
eckhart's avatar
eckhart committed
246
             key_func: KeyFunc = key_tag_name) -> None:
247
248
    """
    Traverses the snytax tree starting with the given ``node`` depth
249
    first and applies the sequences of callback-functions registered
250
    in the ``processing_table``-dictionary.
251
252
253
254
255
256
257
258
259

    The most important use case is the transformation of a concrete
    syntax tree into an abstract tree (AST). But it is also imaginable
    to employ tree-traversal for the semantic analysis of the AST.

    In order to assign sequences of callback-functions to nodes, a
    dictionary ("processing table") is used. The keys usually represent
    tag names, but any other key function is possible. There exist
    three special keys:
260

261
    - '<': always called (before any other processing function)
262
263
    - '*': called for those nodes for which no (other) processing
      function appears in the table
264
    - '>': always called (after any other processing function)
265
266
267
268
269

    Args:
        root_node (Node): The root-node of the syntax tree to be traversed
        processing_table (dict): node key -> sequence of functions that
            will be applied to matching nodes in order. This dictionary
270
271
            is interpreted as a ``compact_table``. See
            :func:`expand_table` or :func:`EBNFCompiler.EBNFTransTable`
272
        key_func (function): A mapping key_func(node) -> keystr. The default
273
            key_func yields node.tag_name.
274

275
276
    Example::

277
        table = { "term": [replace_by_single_child, flatten],
278
                  "factor, flowmarker, retrieveop": replace_by_single_child }
279
        traverse(node, table)
280

281
    """
282

283
284
285
    # Is this optimazation really needed?
    if '__cache__' in processing_table:
        # assume that processing table has already been expanded
eckhart's avatar
eckhart committed
286
        table = processing_table               # type: ProcessingTableType
eckhart's avatar
eckhart committed
287
        cache = cast(TransformationDict, processing_table['__cache__'])  # type: TransformationDict
288
    else:
289
290
        # normalize processing_table entries by turning single values
        # into lists with a single value
291
292
        table = {name: cast(Sequence[Callable], smart_list(call))
                 for name, call in list(processing_table.items())}
293
        table = expand_table(table)
294
        # substitute key for insiginificant whitespace
295
        assert '+' not in table, 'Symbol "+" in processing table is obsolete, use "<" instead'
296
297
        if '~' in table:
            if ':Whitespace' in table:
eckhart's avatar
eckhart committed
298
299
300
301
                raise AssertionError(
                    '"~" is a synonym for ":Whitespace" in the processing table. '
                    'To avoid confusion, choose either of the two, but do not use '
                    'both at the same time!')
302
303
304
305
            whitespace_transformation = table['~']
            del table['~']
            table[':Whitespace'] = whitespace_transformation
        # cache expanded table
eckhart's avatar
eckhart committed
306
307
        cache = cast(TransformationDict,
                     table.setdefault('__cache__', cast(TransformationDict, dict())))
308
309
        # change processing table in place, so its already expanded and cache filled next time
        processing_table.clear()
310
311
        processing_table.update(table)

312
    def traverse_recursive(context):
eckhart's avatar
eckhart committed
313
        nonlocal cache
314
        node = context[-1]
315
        if node.children:
316
            context.append(PLACEHOLDER)
di68kap's avatar
di68kap committed
317
            for child in node.children:
eckhart's avatar
eckhart committed
318
                context[-1] = child
319
                traverse_recursive(context)  # depth first
eckhart's avatar
eckhart committed
320
            context.pop()
321
322

        key = key_func(node)
323
324
325
        try:
            sequence = cache[key]
        except KeyError:
326
            sequence = table.get('<', []) \
327
                + table.get(key, table.get('*', [])) \
328
                + table.get('>', [])
329
330
331
            cache[key] = sequence

        for call in sequence:
332
            call(context)
333

334
    traverse_recursive([root_node])
335
336
    # assert processing_table['__cache__']

337

338
#######################################################################
339
#
340
341
# meta transformations, i.e. transformations that call other
# transformations
342
#
343
#######################################################################
344
345


eckhart's avatar
eckhart committed
346
@transformation_factory(dict)
347
def traverse_locally(context: List[Node],
eckhart's avatar
eckhart committed
348
349
                     processing_table: Dict,              # actually: ProcessingTableType
                     key_func: Callable = key_tag_name):  # actually: KeyFunc
350
351
    """
    Transforms the syntax tree starting from the last node in the context
352
353
354
355
356
357
358
    according to the given processing table. The purpose of this function is
    to apply certain transformations locally, i.e. only for those nodes that
    have the last node in the context as their parent node.
    """
    traverse(context[-1], processing_table, key_func)


359
@transformation_factory(collections.abc.Callable)
360
def apply_if(context: List[Node], transformation: Callable, condition: Callable):
361
362
363
    """
    Applies a transformation only if a certain condition is met.
    """
364
365
366
367
    if condition(context):
        transformation(context)


368
@transformation_factory(collections.abc.Callable)
eckhart's avatar
eckhart committed
369
def apply_unless(context: List[Node], transformation: Callable, condition: Callable):
370
371
372
    """
    Applies a transformation if a certain condition is *not* met.
    """
eckhart's avatar
eckhart committed
373
374
375
376
    if not condition(context):
        transformation(context)


377
378
379
380
381
382
383
384
385
386
387
388
389
390
#######################################################################
#
# conditionals that determine whether the context (or the last node in
# the context for that matter) fulfill a specific condition.
# ---------------------------------------------------------------------
#
# The context of a node is understood as a list of all parent nodes
# leading up to and including the node itself. If represented as list,
# the last element of the list is the node itself.
#
#######################################################################


def is_single_child(context: List[Node]) -> bool:
eckhart's avatar
eckhart committed
391
    """Returns ``True`` if the current node does not have any siblings."""
392
393
394
395
    return len(context[-2].children) == 1


def is_named(context: List[Node]) -> bool:
eckhart's avatar
eckhart committed
396
    """Returns ``True`` if the current node's parser is a named parser."""
397
    return not context[-1].is_anonymous()
398
399
400


def is_anonymous(context: List[Node]) -> bool:
eckhart's avatar
eckhart committed
401
    """Returns ``True`` if the current node's parser is an anonymous parser."""
402
    return context[-1].is_anonymous()
403
404


405
def is_insignificant_whitespace(context: List[Node]) -> bool:
di68kap's avatar
di68kap committed
406
    """Returns ``True`` for whitespace and comments defined with the
407
    ``@comment``-directive."""
408
    return context[-1].tag_name == WHITESPACE_PTYPE
409
410


411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
RX_WHITESPACE = re.compile(r'\s*')


def contains_only_whitespace(context: List[Node]) -> bool:
    """Returns ``True`` for nodes that contain only whitespace regardless
    of the tag_name, i.e. nodes the content of which matches the regular
    expression /\s*/, including empty nodes. Note, that this is not true
    for anonymous whitespace nodes that contain comments."""
    return bool(RX_WHITESPACE.match(context[-1].content))


def is_any_kind_of_whitespace(context: List[Node]) -> bool:
    """Returns ``True`` for nodes that either contain only whitespace or
    are insignificant whitespace nodes, i.e. nodes with the ``tag_name``
    ``PTYPE_WHITESPACE``, including those that contain comment-text."""
    node = context[-1]
    return node.tag_name == WHITESPACE_PTYPE or RX_WHITESPACE.match(node.content)


430
def is_empty(context: List[Node]) -> bool:
eckhart's avatar
eckhart committed
431
    """Returns ``True`` if the current node's content is empty."""
432
433
434
435
    return not context[-1].result


def is_expendable(context: List[Node]) -> bool:
eckhart's avatar
eckhart committed
436
437
    """Returns ``True`` if the current node either is a node containing
    whitespace or an empty node."""
438
    return is_empty(context) or is_insignificant_whitespace(context)
439
440


441
@transformation_factory(collections.abc.Set)
442
def is_token(context: List[Node], tokens: AbstractSet[str] = frozenset()) -> bool:
443
444
    """
    Checks whether the last node in the context has `ptype == TOKEN_PTYPE`
445
446
    and it's content matches one of the given tokens. Leading and trailing
    whitespace-tokens will be ignored. In case an empty set of tokens is passed,
eckhart's avatar
eckhart committed
447
    any token is a match.
448
449
    """
    node = context[-1]
450
    return node.tag_name == TOKEN_PTYPE and (not tokens or node.content in tokens)
451
452


453
@transformation_factory(collections.abc.Set)
454
455
456
457
458
def is_one_of(context: List[Node], tag_name_set: AbstractSet[str]) -> bool:
    """Returns true, if the node's tag_name is one of the given tag names."""
    return context[-1].tag_name in tag_name_set


459
460
461
462
463
464
@transformation_factory(collections.abc.Set)
def not_one_of(context: List[Node], tag_name_set: AbstractSet[str]) -> bool:
    """Returns true, if the node's tag_name is not one of the given tag names."""
    return context[-1].tag_name not in tag_name_set


Eckhart Arnold's avatar
Eckhart Arnold committed
465
466
@transformation_factory(collections.abc.Set)
def matches_re(context: List[Node], patterns: AbstractSet[str]) -> bool:
467
468
    """
    Returns true, if the node's tag_name matches one of the regular
Eckhart Arnold's avatar
Eckhart Arnold committed
469
470
471
472
473
474
475
476
477
    expressions in `patterns`. For example, ':.*' matches all anonymous nodes.
    """
    tn = context[-1].tag_name
    for pattern in patterns:
        if re.match(pattern, tn):
            return True
    return False


eckhart's avatar
eckhart committed
478
@transformation_factory
479
def has_content(context: List[Node], regexp: str) -> bool:
480
481
482
483
484
485
486
487
    """
    Checks a node's content against a regular expression.

    In contrast to ``re.match`` the regular expression must match the complete
    string and not just the beginning of the string to succeed!
    """
    if not regexp.endswith('$'):
        regexp += "$"
488
489
490
    return bool(re.match(regexp, context[-1].content))


491
@transformation_factory(collections.abc.Set)
492
def has_parent(context: List[Node], tag_name_set: AbstractSet[str]) -> bool:
493
494
495
496
    """
    Checks whether a node with one of the given tag names appears somewhere
     in the context before the last node in the context.
     """
497
    for i in range(2, len(context) + 1):
498
499
500
501
502
503
504
505
506
507
508
509
        if context[-i].tag_name in tag_name_set:
            return True
    return False


#######################################################################
#
# utility functions (private)
#
#######################################################################


510
511
512
513
514
515
516
517
518
519
def update_attr(node: Node, child: Node):
    if hasattr(child, '_xml_attr'):
        for k, v in child.attr:
            if k in node.attr and v != node.attr[k]:
                raise ValueError('Conflicting attribute values %s and %s for key %s '
                                 'when reducing %s to %s ! Tree transformation stopped.'
                                 % (v, node.attr[k], k, str(child), str(node)))
            node.attr[k] = v


520
def _replace_by(node: Node, child: Node):
521
522
523
524
    if node.is_anonymous() or not child.is_anonymous():
        node.tag_name = child.tag_name
        # name, ptype = (node.tag_name.split(':') + [''])[:2]
        # child.parser = MockParser(name, ptype)
525
526
        # parser names must not be overwritten, else: child.parser.name = node.parser.name
    node.result = child.result
527
    update_attr(node, child)
528
529


530
def _reduce_child(node: Node, child: Node):
531
    node.result = child.result
532
    update_attr(node, child)
533
534


535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
#######################################################################
#
# rearranging transformations
#
# - tree may be rearranged (e.g.flattened)
# - nodes that are not leaves may be dropped
# - order is preserved
# - leave content is preserved (though not necessarily the leaves
#   themselves)
#
#######################################################################


# @transformation_factory(int, str, Callable)
# def replace_by_child(context: List[Node], criteria: CriteriaType=is_single_child):
#     """
#     Replaces a node by the first of its immediate descendants
#     that meets the `criteria`. The criteria can either be the
#     index of the child (counting from zero), or the tag name or
#     a boolean-valued function on the context of the child.
#     If no child matching the criteria is found, the node will
#     not be replaced.
#     With the default value for `criteria` the same semantics is
#     the same that of `replace_by_single_child`.
#     """
#     child = _pick_child(context, criteria)
#     if child:
#         _replace_by(context[-1], child)
#
#
# @transformation_factory(int, str, Callable)
# def content_from_child(context: List[Node], criteria: CriteriaType = is_single_child):
#     """
#     Reduces a node, by transferring the result of the first of its
#     immediate descendants that meets the `criteria` to this node,
#     but keeping this node's parser entry. The criteria can either
#     be the index of the child (counting from zero), or the tag
#     name or a boolean-valued function on the context of the child.
#     If no child matching the criteria is found, the node will
#     not be replaced.
#     With the default value for `criteria` this has the same semantics
#     as `content_from_single_child`.
#     """
#     child = _pick_child(context, criteria)
#     if child:
#         _reduce_child(context[-1], child)
581
582


583
def flatten_anonymous_nodes(context: List[Node]):
Eckhart Arnold's avatar
Eckhart Arnold committed
584
    """
585
586
587
588
589
    Flattens non-recursively all anonymous non-leaf children by adding
    their result to the result of the parent node. Empty anonymous children
    will be dropped altogether. If the parent node (i.e. `context[-1]) is
    anonymous itself and has only one child node, it will be replaced by
    its single child node.
Eckhart Arnold's avatar
Eckhart Arnold committed
590
    """
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
    node = context[-1]
    if node.children:
        new_result = []
        for child in node.children:
            if child.is_anonymous():
                if child.children:
                    new_result.extend(child.children)
                    update_attr(node, child)
                elif child.result:
                    new_result.append(child)
            else:
                new_result.append(child)
        if len(new_result) == 1:
            child = new_result[0]
            if node.is_anonymous():
                node.tag_name = child.tag_name
Eckhart Arnold's avatar
Eckhart Arnold committed
607
                node.result = child.result
608
                update_attr(node, child)
Eckhart Arnold's avatar
Eckhart Arnold committed
609
                return
610
            elif child.is_anonymous():
Eckhart Arnold's avatar
Eckhart Arnold committed
611
                node.result = child.result
612
                update_attr(node, child)
Eckhart Arnold's avatar
Eckhart Arnold committed
613
                return
614
615
616
        node.result = tuple(new_result)


617
618
def replace_by_single_child(context: List[Node]):
    """
619
620
621
    Removes single branch node, replacing it by its immediate descendant.
    Replacement only takes place, if the last node in the context has
    exactly one child.
622
623
624
    """
    node = context[-1]
    if len(node.children) == 1:
625
        _replace_by(node, node.children[0])
626
627


Eckhart Arnold's avatar
Eckhart Arnold committed
628
def reduce_single_child(context: List[Node]):
629
    """
630
    Reduces a single branch node by transferring the result of its
631
    immediate descendant to this node, but keeping this node's parser entry.
632
633
    Reduction only takes place if the last node in the context has
    exactly one child.
634
635
636
    """
    node = context[-1]
    if len(node.children) == 1:
637
        _reduce_child(node, node.children[0])
638
639


640
@transformation_factory(collections.abc.Callable)
eckhart's avatar
eckhart committed
641
def replace_or_reduce(context: List[Node], condition: Callable = is_named):
642
643
    """
    Replaces node by a single child, if condition is met on child,
644
645
    otherwise (i.e. if the child is anonymous) reduces the child.
    """
646
    node = context[-1]
647
    if len(node.children) == 1:
di68kap's avatar
di68kap committed
648
        child = node.children[0]
649
        if condition(context):   # TODO: bug here?
650
            _replace_by(node, child)
651
        else:
652
            _reduce_child(node, child)
653
654
655


@transformation_factory
656
657
658
def replace_parser(context: List[Node], name: str):
    """
    Replaces the parser of a Node with a mock parser with the given
659
660
661
    name.

    Parameters:
662
        context: the context where the parser shall be replaced
eckhart's avatar
eckhart committed
663
        name: "NAME:PTYPE" of the surrogate. The ptype is optional
664
    """
665
    node = context[-1]
666
    node.tag_name = name
667
668


669
@transformation_factory(collections.abc.Callable)
eckhart's avatar
eckhart committed
670
def flatten(context: List[Node], condition: Callable = is_anonymous, recursive: bool = True):
671
    """
eckhart's avatar
eckhart committed
672
    Flattens all children, that fulfill the given ``condition``
673
674
675
    (default: all unnamed children). Flattening means that wherever a
    node has child nodes, the child nodes are inserted in place of the
    node.
676
677

    If the parameter ``recursive`` is ``True`` the same will recursively be
678
679
680
    done with the child-nodes, first. In other words, all leaves of
    this node and its child nodes are collected in-order as direct
    children of this node.
681
682
683
684

    Applying flatten recursively will result in these kinds of
    structural transformation::

di68kap's avatar
di68kap committed
685
        (1 (+ 2) (+ 3))    ->   (1 + 2 + 3)
686
687
        (1 (+ (2 + (3))))  ->   (1 + 2 + 3)
    """
688

689
    node = context[-1]
690
    if node.children:
Eckhart Arnold's avatar
Eckhart Arnold committed
691
        new_result = []     # type: List[Node]
692
        context.append(PLACEHOLDER)
693
        for child in node.children:
eckhart's avatar
eckhart committed
694
            context[-1] = child
695
            if child.children and condition(context):
696
                if recursive:
697
                    flatten(context, condition, recursive)
698
                new_result.extend(child.children)
699
                update_attr(node, child)
700
701
            else:
                new_result.append(child)
eckhart's avatar
eckhart committed
702
        context.pop()
703
704
705
        node.result = tuple(new_result)


706
def collapse(context: List[Node]):
707
708
709
710
    """
    Collapses all sub-nodes of a node by replacing them with the
    string representation of the node. USE WITH CARE!
    """
711
    node = context[-1]
712
    node.result = node.content
713
714


715
@transformation_factory(collections.abc.Callable)
716
def collapse_if(context: List[Node], condition: Callable, target_tag: str):
717
718
    """
    (Recursively) merges the content of all adjacent child nodes that
719
720
721
722
723
    fulfil the given `condition` into a single leaf node with parser
    `target_tag`. Nodes that do not fulfil the condition will be preserved.

    >>> sxpr = '(place (abbreviation "p.") (page "26") (superscript "b") (mark ",") (page "18"))'
    >>> tree = parse_sxpr(sxpr)
724
    >>> collapse_if([tree], not_one_of({'superscript', 'subscript'}), 'text')
725
    >>> print(flatten_sxpr(tree.as_sxpr()))
726
    (place (text "p.26") (superscript "b") (text ",18"))
727
728
729

    See `test_transform.TestComplexTransformations` for examples.
    """
730

731
732
    assert isinstance(target_tag, str)  # TODO: Delete this when safe

733
    node = context[-1]
eckhart's avatar
eckhart committed
734
735
    package = []  # type: List[Node]
    result = []  # type: List[Node]
736
737
738
739

    def close_package():
        nonlocal package
        if package:
740
            s = "".join(nd.content for nd in package)
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
            result.append(Node(target_tag, s))
            package = []

    for child in node.children:
        if condition([child]):
            if child.children:
                collapse_if([child], condition, target_tag)
                for c in child.children:
                    if condition([c]):
                        package.append(c)
                    else:
                        close_package()
                        result.append(c)
                close_package()
            else:
                package.append(child)
        else:
            close_package()
            result.append(child)
    close_package()
    node.result = tuple(result)


764
@transformation_factory(collections.abc.Callable)
765
def replace_content(context: List[Node], func: Callable):  # Callable[[Node], ResultType]
766
767
    """
    Replaces the content of the node. ``func`` takes the node's result
768
769
    as an argument an returns the mapped result.
    """
770
    node = context[-1]
771
772
773
    node.result = func(node.result)


774
@transformation_factory  # (str)
775
def replace_content_by(context: List[Node], content: str):  # Callable[[Node], ResultType]
776
777
    """
    Replaces the content of the node with the given text content.
778
779
780
781
782
    """
    node = context[-1]
    node.result = content


783
def normalize_whitespace(context):
di68kap's avatar
di68kap committed
784
785
    """
    Normalizes Whitespace inside a leaf node, i.e. any sequence of
786
787
    whitespaces, tabs and linefeeds will be replaced by a single
    whitespace. Empty (i.e. zero-length) Whitespace remains empty,
di68kap's avatar
di68kap committed
788
789
    however.
    """
790
791
    node = context[-1]
    assert not node.children
792
    if is_insignificant_whitespace(context):
793
794
795
        if node.result:
            node.result = ' '
    else:
eckhart's avatar
eckhart committed
796
        node.result = re.sub(r'\s+', ' ', node.result)
797
798


di68kap's avatar
di68kap committed
799
800
801
802
803
804
805
806
807
808
def merge_whitespace(context):
    """
    Merges adjacent whitespace. UNTESTED!
    """
    node = context[-1]
    children = node.children
    new_result = []
    i = 0
    L = len(children)
    while i < L:
809
        if children[i].tag_name == WHITESPACE_PTYPE:
di68kap's avatar
di68kap committed
810
            k = i
811
            while i < L and children[k].tag_name == WHITESPACE_PTYPE:
di68kap's avatar
di68kap committed
812
813
814
815
816
817
818
819
                i += 1
            if i > k:
                children[k].result = sum(children[n].result for n in range(k, i + 1))
            new_result.append(children[k])
        i += 1
    node.result = tuple(new_result)


820
821
@transformation_factory(collections.abc.Callable)
def move_adjacent(context, condition: Callable = is_insignificant_whitespace):
di68kap's avatar
di68kap committed
822
    """
823
    Moves adjacent nodes that fulfill the given condition to the parent node.
824
825
826
827
828
829
    """
    node = context[-1]
    if len(context) <= 1 or not node.children:
        return
    parent = context[-2]
    children = node.children
830
    if condition([children[0]]):
831
832
833
834
        before = (children[0],)
        children = children[1:]
    else:
        before = ()
835
    if children and condition([children[-1]]):
836
837
838
839
840
841
842
843
        after = (children[-1],)
        children = children[:-1]
    else:
        after = tuple()

    if before or after:
        node.result = children
        for i, child in enumerate(parent.children):
844
            if id(child) == id(node):
845
846
847
                break

        # merge adjacent whitespace
eckhart's avatar
eckhart committed
848
849
        prevN = parent.children[i - 1] if i > 0 else None
        nextN = parent.children[i + 1] if i < len(parent.children) - 1 else None
850
        if before and prevN and condition([prevN]):
851
852
            prevN.result = prevN.result + before[0].result
            before = ()
853
        if after and nextN and condition([nextN]):
854
855
856
            nextN.result = after[0].result + nextN.result
            after = ()

857
        parent.result = parent.children[:i] + before + (node,) + after + parent.children[i+1:]
858
859


860
861
862
863
864
#######################################################################
#
# destructive transformations:
#
# - leaves may be dropped (e.g. if deemed irrelevant)
865
# - errors of dropped leaves may be be lost
866
867
868
# - no promise that order will be preserved
#
#######################################################################
869
870


871
@transformation_factory(collections.abc.Callable)
872
873
874
875
876
877
878
879
880
881
882
883
884
def lstrip(context: List[Node], condition: Callable = is_expendable):
    """Recursively removes all leading child-nodes that fulfill a given condition."""
    node = context[-1]
    i = 1
    while i > 0 and node.children:
        lstrip(context + [node.children[0]], condition)
        i, L = 0, len(node.children)
        while i < L and condition(context + [node.children[i]]):
            i += 1
        if i > 0:
            node.result = node.children[i:]


885
@transformation_factory(collections.abc.Callable)
886
887
888
889
890
891
892
893
def rstrip(context: List[Node], condition: Callable = is_expendable):
    """Recursively removes all leading nodes that fulfill a given condition."""
    node = context[-1]
    i, L = 0, len(node.children)
    while i < L and node.children:
        rstrip(context + [node.children[-1]], condition)
        L = len(node.children)
        i = L
eckhart's avatar
eckhart committed
894
        while i > 0 and condition(context + [node.children[i - 1]]):
895
896
897
898
899
            i -= 1
        if i < L:
            node.result = node.children[:i]


900
@transformation_factory(collections.abc.Callable)
eckhart's avatar
eckhart committed
901
def strip(context: List[Node], condition: Callable = is_expendable):
902
903
904
905
906
    """Removes leading and trailing child-nodes that fulfill a given condition."""
    lstrip(context, condition)
    rstrip(context, condition)


907
@transformation_factory  # (slice)
908
def keep_children(context: List[Node], section: slice = slice(None)):
909
    """Keeps only child-nodes which fall into a slice of the result field."""
910
    node = context[-1]
911
    if node.children:
912
        node.result = node.children[section]
913
914


915
@transformation_factory(collections.abc.Callable)
916
917
918
919
920
921
922
def keep_children_if(context: List[Node], condition: Callable):
    """Removes all children for which `condition()` returns `True`."""
    node = context[-1]
    if node.children:
        node.result = tuple(c for c in node.children if condition(context + [c]))


923
@transformation_factory(collections.abc.Set)
eckhart's avatar
eckhart committed
924
def keep_tokens(context: List[Node], tokens: AbstractSet[str] = frozenset()):
925
926
927
928
929
930
    """Removes any among a particular set of tokens from the immediate
    descendants of a node. If ``tokens`` is the empty set, all tokens
    are removed."""
    keep_children_if(context, partial(is_token, tokens=tokens))


931
@transformation_factory(collections.abc.Set)
932
933
934
935
936
937
938
939
940
941
942
def keep_nodes(context: List[Node], tag_names: AbstractSet[str]):
    """Removes children by tag name."""
    keep_children_if(context, partial(is_one_of, tag_name_set=tag_names))


@transformation_factory
def keep_content(context: List[Node], regexp: str):
    """Removes children depending on their string value."""
    keep_children_if(context, partial(has_content, regexp=regexp))


943
@transformation_factory(collections.abc.Callable)
944
def remove_children_if(context: List[Node], condition: Callable):
945
946
947
948
    """Removes all children for which `condition()` returns `True`."""
    node = context[-1]
    if node.children:
        node.result = tuple(c for c in node.children if not condition(context + [c]))
eckhart's avatar
eckhart committed
949
    pass
950

eckhart's avatar
eckhart committed
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
# @transformation_factory(Callable)
# def remove_children(context: List[Node],
#                     condition: Callable = TRUE_CONDITION,
#                     section: slice = slice(None)):
#     """Removes all nodes from a slice of the result field if the function
#     `condition(child_node)` evaluates to `True`."""
#     node = context[-1]
#     if node.children:
#         c = node.children
#         N = len(c)
#         rng = range(*section.indices(N))
#         node.result = tuple(c[i] for i in range(N)
#                             if i not in rng or not condition(context + [c[i]]))
#         # selection = []
#         # for i in range(N):
#         #     context.append(c[i])
#         #     if not i in rng or not condition(context):
#         #         selection.append(c[i])
#         #     context.pop()
#         # if len(selection) != c:
#         #     node.result = tuple(selection)
972
973


974
remove_whitespace = remove_children_if(is_insignificant_whitespace)
975
# partial(remove_children_if, condition=is_whitespace)
976
remove_empty = remove_children_if(is_empty)
di68kap's avatar
di68kap committed
977
remove_anonymous_empty = remove_children_if(lambda ctx: is_empty(ctx) and is_anonymous(ctx))
978
979
980
981
remove_expendables = remove_children_if(is_expendable)
# partial(remove_children_if, condition=is_expendable)
remove_anonymous_expendables = remove_children_if(lambda ctx: is_anonymous(ctx)
                                                  and is_expendable(ctx))
982
remove_anonymous_tokens = remove_children_if(lambda ctx: is_token(ctx) and is_anonymous(ctx))
983
984
985
# remove_first = apply_if(keep_children(slice(1, None)), lambda ctx: len(ctx[-1].children) > 1)
# remove_last = apply_if(keep_children(slice(None, -1)), lambda ctx: len(ctx[-1].children) > 1)
# remove_brackets = apply_if(keep_children(slice(1, -1)), lambda ctx: len(ctx[-1].children) >= 2)
986
remove_infix_operator = keep_children(slice(0, None, 2))
987
remove_single_child = apply_if(keep_children(slice(0)), lambda ctx: len(ctx[-1].children) == 1)
988
989


990
991
992
993
994
def remove_first(context: List[Node]):
    """Removes the first non-whitespace child."""
    node = context[-1]
    if node.children:
        for i, child in enumerate(node.children):
995
            if child.tag_name != WHITESPACE_PTYPE:
996
997
998
                break
        else:
            return
eckhart's avatar
eckhart committed
999
        node.result = node.children[:i] + node.children[i + 1:]