syntaxtree.py 50.6 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
# syntaxtree.py - syntax tree classes 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
Module ``syntaxtree`` defines the ``Node``-class for syntax trees as well
as an abstract base class for parser-objects. The latter is defined
eckhart's avatar
eckhart committed
22
here, because node-objects refer to parser-objects. All concrete
23 24 25
parser classes are defined in the ``parse`` module.
"""

26
from collections import OrderedDict
eckhart's avatar
eckhart committed
27
import copy
28
import json
29
from typing import Callable, cast, Iterator, List, AbstractSet, Set, Union, Tuple, Optional, Dict
30

eckhart's avatar
eckhart committed
31
from DHParser.error import Error, ErrorCode, linebreaks, line_col
32
from DHParser.stringview import StringView
33
from DHParser.toolkit import get_config_value, re
di68kap's avatar
di68kap committed
34

35

di68kap's avatar
di68kap committed
36
__all__ = ('WHITESPACE_PTYPE',
37
           'TOKEN_PTYPE',
38 39
           'ZOMBIE_TAG',
           'PLACEHOLDER',
eckhart's avatar
eckhart committed
40 41 42
           'ResultType',
           'StrictResultType',
           'ChildrenType',
43
           'Node',
44
           'serialize',
45
           'FrozenNode',
46
           'tree_sanity_check',
di68kap's avatar
di68kap committed
47
           'RootNode',
48
           'parse_sxpr',
49
           'parse_xml',
50
           'parse_json_syntaxtree',
eckhart's avatar
eckhart committed
51
           'parse_tree',
52 53
           'flatten_sxpr',
           'flatten_xml')
Eckhart Arnold's avatar
Eckhart Arnold committed
54 55


56 57 58 59 60 61 62 63
#######################################################################
#
# parser base and mock parsers
#
#######################################################################


WHITESPACE_PTYPE = ':Whitespace'
64
TOKEN_PTYPE = ':Token'
65

66
ZOMBIE_TAG = "__ZOMBIE__"
67

68 69 70 71 72 73 74
#######################################################################
#
# syntaxtree nodes
#
#######################################################################


eckhart's avatar
eckhart committed
75 76
RX_IS_SXPR = re.compile(r'\s*\(')
RX_IS_XML = re.compile(r'\s*<')
77
RX_ATTR_NAME = re.compile(r'[\w.:-]')
eckhart's avatar
eckhart committed
78 79


80
def flatten_sxpr(sxpr: str, threshold: int = -1) -> str:
81 82
    """
    Returns S-expression ``sxpr`` as a one-liner without unnecessary
Eckhart Arnold's avatar
Eckhart Arnold committed
83 84
    whitespace.

85 86 87 88 89 90 91
    The ``threshold`` value is a maximum number of
    characters allowed in the flattened expression. If this number
    is exceeded the the unflattened S-expression is returned. A
    negative number means that the S-expression will always be
    flattened. Zero or (any postive integer <= 3) essentially means
    that the expression will not be flattened.

Eckhart Arnold's avatar
Eckhart Arnold committed
92
    Example:
Eckhart Arnold's avatar
Eckhart Arnold committed
93
    >>> flatten_sxpr('(a\\n    (b\\n        c\\n    )\\n)\\n')
Eckhart Arnold's avatar
Eckhart Arnold committed
94 95
    '(a (b c))'
    """
eckhart's avatar
eckhart committed
96 97 98
    assert RX_IS_SXPR.match(sxpr)
    if threshold == 0:
        return sxpr
99
    flat = re.sub(r'\s(?=\))', '', re.sub(r'\s+', ' ', sxpr)).strip()
eckhart's avatar
eckhart committed
100
    if len(flat) > threshold >= 0:
101 102
        return sxpr.strip()
    return flat
Eckhart Arnold's avatar
Eckhart Arnold committed
103 104


105
def flatten_xml(xml: str) -> str:
106 107
    """
    Returns an XML-tree as a one liner without unnecessary whitespace,
108
    i.e. only whitespace within leaf-nodes is preserved.
109 110
    A more precise alternative to `flatten_xml` is to use Node.as_xml()
    ans passing a set containing the top level tag to parameter `inline_tags`.
111
    """
112 113
    # works only with regex
    # return re.sub(r'\s+(?=<\w)', '', re.sub(r'(?<=</\w+>)\s+', '', xml))
eckhart's avatar
eckhart committed
114
    assert RX_IS_XML.match(xml)
eckhart's avatar
eckhart committed
115

116 117
    def tag_only(m):
        return m.groupdict()['closing_tag']
118
    return re.sub(r'\s+(?=<[\w:])', '', re.sub(r'(?P<closing_tag></:?\w+>)\s+', tag_only, xml))
119 120


121 122 123 124 125
ChildrenType = Tuple['Node', ...]
NoChildren = cast(ChildrenType, ())  # type: ChildrenType
StrictResultType = Union[ChildrenType, StringView, str]
ResultType = Union[ChildrenType, 'Node', StringView, str, None]

eckhart's avatar
eckhart committed
126
RX_AMP = re.compile(r'&(?!\w+;)')
127 128


Eckhart Arnold's avatar
Eckhart Arnold committed
129
class Node:  # (collections.abc.Sized): Base class omitted for cython-compatibility
130 131 132
    """
    Represents a node in the concrete or abstract syntax tree.

133 134
    TODO: Add some documentation and doc-tests here...

eckhart's avatar
eckhart committed
135
    Attributes and Properties:
136 137
        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
138

139 140 141
        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.
142

143 144
        children (tuple):  The tuple of child nodes or an empty tuple
            if there are no child nodes. READ ONLY!
145

eckhart's avatar
eckhart committed
146 147 148 149
        content (str):  Yields the contents of the tree as string. The
            difference to ``str(node)`` is that ``node.content`` does
            not add the error messages to the returned string.

150 151 152
        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
153
            the length before AST-transformation and will never change
154
            through AST-transformation. READ ONLY!
155

156 157
        pos (int):  the position of the node within the parsed text.

Eckhart Arnold's avatar
Eckhart Arnold committed
158
            The value of ``pos`` is -1 meaning invalid by default.
159
            Setting this value will set the positions of all child
Eckhart Arnold's avatar
Eckhart Arnold committed
160
            nodes relative to this value.
161 162

            To set the pos values of all nodes in a syntax tree, the
Eckhart Arnold's avatar
Eckhart Arnold committed
163
            pos value of the root node should be set to 0 right
164 165
            after parsing.

Eckhart Arnold's avatar
Eckhart Arnold committed
166
            Other than that, this value should be considered READ ONLY.
167 168
            At any rate, it should only be reassigned during the parsing
            stage and never during or after the AST-transformation.
169

170 171
        attr (dict): An optional dictionary of XML-attr. This
            dictionary is created lazily upon first usage. The attr
172 173
            will only be shown in the XML-Representation, not in the
            S-Expression-output.
174
    """
175

176
    __slots__ = '_result', 'children', '_pos', 'tag_name', '_xml_attr'
177

178
    def __init__(self, tag_name: str, result: ResultType, leafhint: bool = False) -> None:
179 180
        """
        Initializes the ``Node``-object with the ``Parser``-Instance
181 182
        that generated the node and the parser's result.
        """
eckhart's avatar
eckhart committed
183
        self._pos = -1                  # type: int
184
        # Assignment to self.result initializes the attr _result, children and _len
di68kap's avatar
di68kap committed
185
        # The following if-clause is merely an optimization, i.e. a fast-path for leaf-Nodes
186
        if leafhint:
eckhart's avatar
eckhart committed
187
            self._result = result       # type: StrictResultType  # cast(StrictResultType, result)
188 189 190
            self.children = NoChildren  # type: ChildrenType
        else:
            self.result = result
191
        self.tag_name = tag_name        # type: str
192

eckhart's avatar
eckhart committed
193

eckhart's avatar
eckhart committed
194 195
    def __deepcopy__(self, memo):
        if self.children:
196
            duplicate = self.__class__(self.tag_name, copy.deepcopy(self.children), False)
eckhart's avatar
eckhart committed
197
        else:
198
            duplicate = self.__class__(self.tag_name, self.result, True)
eckhart's avatar
eckhart committed
199
        duplicate._pos = self._pos
eckhart's avatar
eckhart committed
200
        if self.attr_active():
di68kap's avatar
di68kap committed
201 202
            duplicate.attr.update(copy.deepcopy(self._xml_attr))
            # duplicate._xml_attr = copy.deepcopy(self._xml_attr)  # this is not cython compatible
eckhart's avatar
eckhart committed
203
        return duplicate
Eckhart Arnold's avatar
Eckhart Arnold committed
204

eckhart's avatar
eckhart committed
205

206
    def __str__(self):
207 208
        if isinstance(self, RootNode):
            root = cast(RootNode, self)
209
            errors = root.errors_sorted
210 211
            if errors:
                e_pos = errors[0].pos
Eckhart Arnold's avatar
Eckhart Arnold committed
212
                content = self.content
eckhart's avatar
eckhart committed
213 214
                return content[:e_pos] + ' <<< Error on "%s" | %s >>> ' % \
                    (content[e_pos - self.pos:], '; '.join(e.message for e in errors))
215
        return self.content
Eckhart Arnold's avatar
Eckhart Arnold committed
216

eckhart's avatar
eckhart committed
217

218
    def __repr__(self):
219
        # mpargs = {'name': self.parser.name, 'ptype': self.parser.ptype}
220 221
        # name, ptype = (self._tag_name.split(':') + [''])[:2]
        # parg = "MockParser({name}, {ptype})".format(name=name, ptype=ptype)
222
        rarg = str(self) if not self.children else \
223
            "(" + ", ".join(child.__repr__() for child in self.children) + ")"
224
        return "Node(%s, %s)" % (self.tag_name, rarg)
225

Eckhart Arnold's avatar
Eckhart Arnold committed
226

227
    def __len__(self):
228 229
        return (sum(len(child) for child in self.children)
                if self.children else len(self._result))
230 231 232


    def __bool__(self):
233 234 235 236
        """Returns the bool value of a node, which is always True. The reason
        for this is that a boolean test on a variable that can contain a node
        or None will only yield `False` in case of None.
        """
237 238 239
        return True


240
    def __hash__(self):
241
        return hash(self.tag_name)
242

Eckhart Arnold's avatar
Eckhart Arnold committed
243

244 245 246
    def __getitem__(self, index_or_tagname: Union[int, str]) -> Union['Node', Iterator['Node']]:
        """
        Returns the child node with the given index if ``index_or_tagname`` is
247
        an integer or the first child node with the given tag name. Examples::
248

249
            >>> tree = parse_sxpr('(a (b "X") (X (c "d")) (e (X "F")))')
250 251
            >>> flatten_sxpr(tree[0].as_sxpr())
            '(b "X")'
252 253
            >>> flatten_sxpr(tree["X"].as_sxpr())
            '(X (c "d"))'
254 255 256 257

        Args:
            index_or_tagname(str): Either an index of a child node or a
                tag name.
258
        Returns:
259 260
            Node: All nodes which have a given tag name.
        """
261 262 263
        if self.children:
            if isinstance(index_or_tagname, int):
                return self.children[index_or_tagname]
264
            else:
265 266 267 268 269
                for child in self.children:
                    if child.tag_name == index_or_tagname:
                        return child
                raise KeyError(index_or_tagname)
        raise ValueError('Leave nodes have no children that can be indexed!')
270 271 272 273


    def __contains__(self, tag_name: str) -> bool:
        """
274
        Returns true if a child with the given tag name exists.
275
        Args:
276 277
            tag_name (str): tag_name which will be searched among to immediate
                descendants of this node.
278 279 280 281
        Returns:
            bool:  True, if at least one descendant node with the given tag
                name exists, False otherwise
        """
282 283 284 285 286
        # assert isinstance(tag_name, str)
        if self.children:
            for child in self.children:
                if child.tag_name == tag_name:
                    return True
287
            return False
288
        raise ValueError('Leave node cannot contain other nodes')
289 290


291
    def equals(self, other: 'Node') -> bool:
292
        """
293 294 295 296 297 298
        Equality of value: Two nodes are considered as having the same value,
        if their tag name is the same, if their results are equal and
        if their attributes and attribute values are the same.

        Returns True, if the tree originating in node `self` is equal by
        value to the tree originating in node `other`.
299 300 301 302 303 304 305 306 307 308
        """
        if self.tag_name == other.tag_name and self.compare_attr(other):
            if self.children:
                return (len(self.children) == len(other.children)
                        and all(a.equals(b) for a, b in zip(self.children, other.children)))
            else:
                return self.result == other.result
        return False


309 310 311 312 313 314 315 316 317 318 319 320 321 322
    def get(self, index_or_tagname: Union[int, str],
            surrogate: Union['Node', Iterator['Node']]) -> Union['Node', Iterator['Node']]:
        """Returns the child node with the given index if ``index_or_tagname``
        is an integer or the first child node with the given tag name. If no
        child with the given index or tag_name exists, the ``surrogate`` is
        returned instead. This mimics the behaviour of Python's dictionary's
        get-method.
        """
        try:
            return self[index_or_tagname]
        except KeyError:
            return surrogate


323
    def is_anonymous(self) -> bool:
Eckhart Arnold's avatar
Eckhart Arnold committed
324
        return not self.tag_name or self.tag_name[0] == ':'
325

Eckhart Arnold's avatar
Eckhart Arnold committed
326

327
    @property
Eckhart Arnold's avatar
Eckhart Arnold committed
328
    def result(self) -> StrictResultType:
329 330 331 332 333
        """
        Returns the result from the parser that created the node.
        Error messages are not included in the result. Use `self.content()`
        if the result plus any error messages is needed.
        """
334 335
        return self._result

336

337
    @result.setter
Eckhart Arnold's avatar
Eckhart Arnold committed
338
    def result(self, result: ResultType):
Eckhart Arnold's avatar
Eckhart Arnold committed
339
        # # made obsolete by static type checking with mypy
eckhart's avatar
eckhart committed
340 341 342 343
        # assert ((isinstance(result, tuple) and all(isinstance(child, Node) for child in result))
        #         or isinstance(result, Node)
        #         or isinstance(result, str)
        #         or isinstance(result, StringView)), "%s (%s)" % (str(result), str(type(result)))
Eckhart Arnold's avatar
Eckhart Arnold committed
344 345
        # Possible optimization: Do not allow single nodes as argument:
        # assert not isinstance(result, Node)
346
        # self._content = None
347 348 349 350 351 352 353 354 355
        if isinstance(result, Node):
            self.children = (result,)
            self._result = self.children
        else:
            if isinstance(result, tuple):
                self.children = result
                self._result = result or ''
            else:
                self.children = NoChildren
eckhart's avatar
eckhart committed
356
                self._result = result  # cast(StrictResultType, result)
357

358

359 360 361 362 363 364 365 366 367 368 369 370
    def _content(self) -> List[str]:
        """
        Returns string content as list of string fragments
        that are gathered from all child nodes in order.
        """
        if self.children:
            fragments = []
            for child in self.children:
                fragments.extend(child._content())
            return fragments
        self._result = str(self._result)
        return [self._result]
371

372

373
    @property
eckhart's avatar
eckhart committed
374
    def content(self) -> str:
375
        """
376 377 378
        Returns content as string. If the node has child-nodes, the
        string content of the child-nodes is recursively read and then
        concatenated.
379
        """
380 381 382 383 384 385 386 387
        if self.children:
            fragments = []
            for child in self.children:
                fragments.extend(child._content())
            return ''.join(fragments)
        self._result = str(self._result)
        return self._result
        # unoptimized
Eckhart Arnold's avatar
Eckhart Arnold committed
388 389
        # return "".join(child.content for child in self.children) if self.children \
        #     else str(self._result)
di68kap's avatar
di68kap committed
390 391


392
    @property
393
    def pos(self) -> int:
eckhart's avatar
eckhart committed
394 395
        """Returns the position of the Node's content in the source text."""
        if self._pos < 0:
Eckhart Arnold's avatar
Eckhart Arnold committed
396
            raise AssertionError("Position value not initialized! Use Node.with_pos()")
397 398
        return self._pos

eckhart's avatar
eckhart committed
399

Eckhart Arnold's avatar
Eckhart Arnold committed
400
    def with_pos(self, pos: int) -> 'Node':
eckhart's avatar
eckhart committed
401
        """
Eckhart Arnold's avatar
Eckhart Arnold committed
402
        Initialize position value. Usually, the parser guard
eckhart's avatar
eckhart committed
403 404
        (`parsers.add_parser_guard()`) takes care of assigning the
        position in the document to newly created nodes. However,
Eckhart Arnold's avatar
Eckhart Arnold committed
405
        when Nodes are created outside the reach of the parser
eckhart's avatar
eckhart committed
406
        guard, their document-position must be assigned manually.
Eckhart Arnold's avatar
Eckhart Arnold committed
407 408
        Position values of the child nodes are assigned recursively, too.
        Returns the node itself for convenience.
eckhart's avatar
eckhart committed
409
        """
410 411 412 413
        # condition self.pos == pos cannot be assumed when tokens or whitespace
        # are dropped early!
        # assert self._pos < 0 or self.pos == pos, ("pos mismatch %i != %i at Node: %s"
        #                                           % (self._pos, pos, repr(self)))
Eckhart Arnold's avatar
Eckhart Arnold committed
414 415 416 417 418 419 420 421 422 423
        if pos != self._pos >= 0:
            raise AssertionError("Position value cannot be reassigned to a different value!")
        if self._pos < 0:
            self._pos = pos
            # recursively adjust pos-values of all children
            offset = self.pos
            for child in self.children:
                if child._pos < 0:
                    child.with_pos(offset)
                offset = child.pos + len(child)
eckhart's avatar
eckhart committed
424 425
        return self

426

427 428 429 430 431 432 433 434 435 436 437 438 439
    @property
    def attr(self):
        """
        Returns a dictionary of XML-attr attached to the node.
        """
        try:
            if self._xml_attr is None:          # cython compatibility
                self._xml_attr = OrderedDict()
        except AttributeError:
            self._xml_attr = OrderedDict()
        return self._xml_attr


eckhart's avatar
eckhart committed
440 441 442 443 444 445 446 447 448 449 450 451 452
    def attr_active(self) -> bool:
        """
        Returns True, if XML-Attributes of this node have ever been set
        or queried, even if unsuccessfully.
        """
        try:
            if self._xml_attr is not None:
                return True
        except AttributeError:
            pass
        return False


453
    def compare_attr(self, other: 'Node') -> bool:
454
        """
455 456
        Returns True, if `self` and `other` have the same attributes with the
        same attribute values.
457
        """
458 459 460 461 462 463 464 465 466
        if self.attr_active():
            if other.attr_active():
                return self.attr == other.attr
            return len(self.attr) == 0
            # self has empty dictionary and other has no attributes
        elif other.attr_active():
            return len(other.attr) == 0
            # other has empty attribute dictionary and self as no attributes
        return True  # neither self nor other have any attributes
467

Eckhart Arnold's avatar
Eckhart Arnold committed
468

469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523
    def select(self, match_function: Callable, include_root: bool = False, reverse: bool = False) \
            -> Iterator['Node']:
        """
        Finds nodes in the tree that fulfill a given criterion.

        `select` is a generator that yields all nodes for which the
        given `match_function` evaluates to True. The tree is
        traversed pre-order.

        See function `Node.select_by_tag` for some examples.

        Args:
            match_function (function): A function  that takes as Node
                object as argument and returns True or False
            include_root (bool): If False, only descendant nodes will be
                checked for a match.
            reverse (bool): If True, the tree will be walked in reverse
                order, i.e. last children first.
        Yields:
            Node: All nodes of the tree for which
            ``match_function(node)`` returns True
        """
        if include_root and match_function(self):
            yield self
        child_iterator = reversed(self.children) if reverse else self.children
        for child in child_iterator:
            if match_function(child):
                yield child
            yield from child.select(match_function, False, reverse)
        # The above variant is slightly faster
        # for child in child_iterator:
        #     yield from child.select(match_function, True, reverse)


    def select_by_tag(self, tag_names: Union[str, AbstractSet[str]],
                      include_root: bool = False) -> Iterator['Node']:
        """
        Returns an iterator that runs through all descendants that have one
        of the given tag names.

        Examples::

            >>> tree = parse_sxpr('(a (b "X") (X (c "d")) (e (X "F")))')
            >>> list(flatten_sxpr(item.as_sxpr()) for item in tree.select_by_tag("X", False))
            ['(X (c "d"))', '(X "F")']
            >>> list(flatten_sxpr(item.as_sxpr()) for item in tree.select_by_tag({"X", "b"}, False))
            ['(b "X")', '(X (c "d"))', '(X "F")']
            >>> any(tree.select_by_tag('a', False))
            False
            >>> list(flatten_sxpr(item.as_sxpr()) for item in tree.select_by_tag('a', True))
            ['(a (b "X") (X (c "d")) (e (X "F")))']
            >>> flatten_sxpr(next(tree.select_by_tag("X", False)).as_sxpr())
            '(X (c "d"))'

        Args:
eckhart's avatar
eckhart committed
524
            tag_names(set): A tag name or set of tag names that is being
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
                searched for
            include_root (bool): If False, only descendant nodes will be
                checked for a match.
        Yields:
            Node: All nodes which have a given tag name.
        """
        if isinstance(tag_names, str):
            tag_names = frozenset({tag_names})
        return self.select(lambda node: node.tag_name in tag_names, include_root)


    def pick(self, tag_names: Union[str, Set[str]]) -> Optional['Node']:
        """
        Picks the first descendant with one of the given tag_names.

        This function is mostly just syntactic sugar for
        ``next(node.select_by_tag(tag_names, False))``. However, rather than
        raising a StopIterationError if no descendant with the given tag-name
        exists, it returns None.
        """
        try:
            return next(self.select_by_tag(tag_names, False))
        except StopIteration:
            return None


    def tree_size(self) -> int:
        """
        Recursively counts the number of nodes in the tree including the root node.
        """
        return sum(child.tree_size() for child in self.children) + 1

    #
    # serialization methods
    #

561
    def _tree_repr(self, tab, open_fn, close_fn, data_fn=lambda i: i,
562
                   density=0, inline=False, inline_fn=lambda node: False) -> str:
563 564 565 566 567 568 569 570
        """
        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.

571
        Args:
572
            tab (str):  The indentation string, e.g. '\t' or '    '
eckhart's avatar
eckhart committed
573
            open_fn:   (Node->str) A function that returns an opening
574
                string (e.g. an XML-tag_name) for a given node
eckhart's avatar
eckhart committed
575
            close_fn:  (Node->str) A function that returns a closeF
576
                string (e.g. an XML-tag_name) for a given node.
eckhart's avatar
eckhart committed
577
            data_fn:   (str->str) A function that filters the data string
578 579 580 581 582 583
                before printing, e.g. to add quotation marks

        Returns (str):
            A string that contains a (serialized) tree representation
            of the node and its children.
        """
eckhart's avatar
eckhart committed
584 585
        head = open_fn(self)
        tail = close_fn(self)
586 587

        if not self.result:
588
            return head.rstrip() + tail.lstrip()
589

eckhart's avatar
eckhart committed
590
        tail = tail.lstrip(None if density & 2 else '')
591

592
        inline = inline or inline_fn(self)
593 594 595 596 597
        if inline:
            head = head.rstrip()
            tail = tail.lstrip()
            usetab, sep = '', ''
        else:
eckhart's avatar
eckhart committed
598 599
            usetab = tab if head else ''    # no indentation if tag is already omitted
            sep = '\n'
600

601 602
        if self.children:
            content = []
603
            for child in self.children:
604
                subtree = child._tree_repr(tab, open_fn, close_fn, data_fn,
605
                                           density, inline, inline_fn)
eckhart's avatar
eckhart committed
606
                if subtree:
eckhart's avatar
eckhart committed
607 608
                    st = [subtree] if inline else subtree.split('\n')
                    content.append((sep + usetab).join(s for s in st))
609
            return head + usetab + (sep + usetab).join(content) + tail
610

eckhart's avatar
eckhart committed
611
        res = self.content
eckhart's avatar
eckhart committed
612
        if not inline and not head:
eckhart's avatar
eckhart committed
613
            # strip whitespace for omitted non inline node, e.g. CharData in mixed elements
eckhart's avatar
eckhart committed
614
            res = res.strip()
615 616
        if density & 1 and res.find('\n') < 0:  # and head[0] == "<":
            # except for XML, add a gap between opening statement and content
617
            gap = ' ' if not inline and head and head.rstrip()[-1:] != '>' else ''
eckhart's avatar
eckhart committed
618
            return head.rstrip() + gap + data_fn(res) + tail.lstrip()
619
        else:
620
            return head + '\n'.join([usetab + data_fn(s) for s in res.split('\n')]) + tail
621

Eckhart Arnold's avatar
Eckhart Arnold committed
622

623
    def as_sxpr(self, src: Optional[str] = None,
624
                indentation: int = 2,
625
                compact: bool = False,
eckhart's avatar
eckhart committed
626
                flatten_threshold: int = 92) -> str:
627
        """
628
        Returns content as S-expression, i.e. in lisp-like form. If this
eckhart's avatar
eckhart committed
629
        method is called on a RootNode-object,
630

631
        Args:
632 633
            src:  The source text or `None`. In case the source text is
                given the position of the element in the text will be
634 635 636
                reported as position, line, column. In case the empty string is
                given rather than None, only the position value will be
                reported in case it has been initialized, i.e. pos >= 0.
637 638
            indentation: The number of whitespaces for indentation
            compact:  If True, a compact representation is returned where
639
                brackets are omitted and only the indentation indicates the
Eckhart Arnold's avatar
Eckhart Arnold committed
640
                tree structure.
641 642 643
            flatten_threshold:  Return the S-expression in flattened form if
                the flattened expression does not exceed the threshold length.
                A negative number means that it will always be flattened.
644 645
        """

eckhart's avatar
eckhart committed
646
        left_bracket, right_bracket, density = ('', '', 1) if compact else ('(', '\n)', 0)
eckhart's avatar
eckhart committed
647
        lbreaks = linebreaks(src) if src else []  # type: List[int]
648
        root = cast(RootNode, self) if isinstance(self, RootNode) else None  # type: Optional[RootNode]
649

650
        def opening(node: Node) -> str:
eckhart's avatar
eckhart committed
651
            """Returns the opening string for the representation of `node`."""
eckhart's avatar
eckhart committed
652
            txt = [left_bracket, node.tag_name]
653
            # s += " '(pos %i)" % node.add_pos
654
            # txt.append(str(id(node)))  # for debugging
eckhart's avatar
eckhart committed
655
            if node.attr_active():
656
                txt.extend(' `(%s "%s")' % (k, v) for k, v in node.attr.items())
657
            if src:
658
                line, col = line_col(lbreaks, node.pos)
659 660 661
                txt.append(' `(pos %i %i %i)' % (node.pos, line, col))
            elif src is not None and node._pos >= 0:
                txt.append(' `(pos %i)' % node.pos)
662 663
            if root and id(node) in root.error_nodes:
                txt.append(" `(err `%s)" % ' '.join(str(err) for err in root.get_errors(node)))
664
            return "".join(txt) + '\n'
665

666
        def closing(node: Node) -> str:
eckhart's avatar
eckhart committed
667 668
            """Returns the closing string for the representation of `node`."""
            return right_bracket
669

670
        def pretty(strg: str) -> str:
eckhart's avatar
eckhart committed
671 672 673 674
            """Encloses `strg` with the right kind of quotation marks."""
            return '"%s"' % strg if strg.find('"') < 0 \
                else "'%s'" % strg if strg.find("'") < 0 \
                else '"%s"' % strg.replace('"', r'\"')
675

676
        sxpr = self._tree_repr(' ' * indentation, opening, closing, pretty, density=density)
eckhart's avatar
eckhart committed
677
        return sxpr if compact else flatten_sxpr(sxpr, flatten_threshold)
Eckhart Arnold's avatar
Eckhart Arnold committed
678

eckhart's avatar
eckhart committed
679

680 681
    def as_xml(self, src: str = None,
               indentation: int = 2,
eckhart's avatar
eckhart committed
682 683 684
               inline_tags: Set[str] = set(),
               omit_tags: Set[str] = set(),
               empty_tags: Set[str] = set()) -> str:
685 686 687
        """
        Returns content as XML-tree.

688
        Args:
689 690
            src:  The source text or `None`. In case the source text is given,
                the position will also be reported as line and column.
691
            indentation: The number of whitespaces for indentation
692 693 694
            inline_tags:  A set of tag names, the content of which will always be written
                on a single line, unless it contains explicit line feeds ('\n').
            omit_tags:  A set of tags from which only the content will be printed, but
695
                neither the opening tag nor its attr nor the closing tag. This
696 697 698
                allows producing a mix of plain text and child tags in the output,
                which otherwise is not supported by the Node object, because it
                requires its content to be either a tuple of children or string content.
699 700
            empty_tags:  A set of tags which shall be rendered as empty elements, e.g.
                "<empty/>" instead of "<empty><empty>".
701
        """
702
        root = cast(RootNode, self) if isinstance(self, RootNode) else None  # type: Optional[RootNode]
703

704
        def opening(node: Node) -> str:
705 706 707
            """Returns the opening string for the representation of `node`."""
            if node.tag_name in omit_tags:
                return ''
eckhart's avatar
eckhart committed
708
            txt = ['<', node.tag_name]
eckhart's avatar
eckhart committed
709
            has_reserved_attrs = node.attr_active() \
eckhart's avatar
eckhart committed
710
                and any(r in node.attr for r in {'err', 'line', 'col'})
eckhart's avatar
eckhart committed
711
            if node.attr_active():
712
                txt.extend(' %s="%s"' % (k, v) for k, v in node.attr.items())
713
            if src and not has_reserved_attrs:
eckhart's avatar
eckhart committed
714
                txt.append(' line="%i" col="%i"' % line_col(line_breaks, node.pos))
715 716
            if src == '' and not (node.attr_active() and '_pos' in node.attr) and node.pos >= 0:
                txt.append(' _pos="%i"' % node.pos)
717
            if root and id(node) in root.error_nodes and not has_reserved_attrs:
eckhart's avatar
eckhart committed
718
                txt.append(' err="%s"' % ''.join(str(err).replace('"', r'\"')
eckhart's avatar
eckhart committed
719
                                                 for err in root.get_errors(node)))
720 721 722
            if node.tag_name in empty_tags:
                assert not node.result, ("Node %s with content %s is not an empty element!" %
                                         (node.tag_name, str(node)))
eckhart's avatar
eckhart committed
723
                ending = "/>\n" if not node.tag_name[0] == '?' else "?>\n"
724 725 726
            else:
                ending = ">\n"
            return "".join(txt + [ending])
727

728
        def closing(node: Node):
729
            """Returns the closing string for the representation of `node`."""
730
            if node.tag_name in omit_tags or node.tag_name in empty_tags:
731
                return ''
eckhart's avatar
eckhart committed
732
            return '\n</' + node.tag_name + '>'
733

734 735 736 737 738 739
        def sanitizer(content: str) -> str:
            """Substitute "&", "<", ">" in XML-content by the respective entities."""
            content = RX_AMP.sub('&amp;', content)
            content = content.replace('<', '&lt;').replace('>', '&gt;')
            return content

740
        def inlining(node: Node):
741 742 743 744
            """Returns True, if `node`'s tag name is contained in `inline_tags`,
            thereby signalling that the children of this node shall not be
            printed on several lines to avoid unwanted gaps in the output.
            """
eckhart's avatar
eckhart committed
745
            return node.tag_name in inline_tags \
eckhart's avatar
eckhart committed
746
                or (node.attr_active()
eckhart's avatar
eckhart committed
747
                    and node.attr.get('xml:space', 'default') == 'preserve')
748

749
        line_breaks = linebreaks(src) if src else []
750
        return self._tree_repr(' ' * indentation, opening, closing, sanitizer,
751
                               density=1, inline_fn=inlining)
752

Eckhart Arnold's avatar
Eckhart Arnold committed
753

754
    def to_json_obj(self) -> Dict:
eckhart's avatar
eckhart committed
755
        """Serialize a node or tree as json-object"""
Eckhart Arnold's avatar
Eckhart Arnold committed
756 757 758
        data = [self.tag_name,
                [child.to_json_obj() for child in self.children]
                if self.children else str(self._result)]
759 760 761 762 763 764
        has_attr = self.attr_active()
        if self._pos >= 0 or has_attr:
            data.append(self._pos)
        if has_attr:
            data.append(dict(self._xml_attr))
        return { '__class__': 'DHParser.Node', 'data': data }
765 766


767 768
    @staticmethod
    def from_json_obj(json_obj: Dict) -> 'Node':
769 770 771 772 773 774
        """Convert a json object representing a node (or tree) back into a
        Node object. Raises a ValueError, if `json_obj` does not represent
        a node."""
        if json_obj.get('__class__', '') != 'DHParser.Node':
            raise ValueError('JSON object: ' + str(json_obj) +
                             ' does not represent a Node object.')
775
        tag_name, result, pos, attr = (json_obj['data'] + [-1, None])[:4]
776
        if isinstance(result, str):
777 778 779 780 781 782 783
            leafhint = True
        else:
            leafhint = False
            result = tuple(Node.from_json_obj(child) for child in result)
        node = Node(tag_name, result, leafhint)
        node._pos = pos
        if attr:
784
            node.attr.update(attr)
785
        return node
786

787 788 789 790
    def as_json(self, indent: Optional[int] = 2, ensure_ascii=False) -> str:
        return json.dumps(self.to_json_obj(), indent=indent, ensure_ascii=ensure_ascii,
                          separators=(', ', ': ') if indent is not None else (',', ':'))

791

eckhart's avatar
eckhart committed
792
def serialize(node: Node, how: str = 'default') -> str:
793
    """
794
    Serializes the tree starting with `node` either as S-expression, XML, JSON,
795
    or in compact form. Possible values for `how` are 'S-expression',
796
    'XML', 'JSON', 'compact' accordingly, or 'AST', 'CST', 'default' in which case
797 798 799 800 801 802 803 804 805 806 807 808 809
    the value of respective configuration variable determines the
    serialization format. (See module `configuration.py`.)
    """
    switch = how.lower()

    if switch == 'ast':
        switch = get_config_value('ast_serialization').lower()
    elif switch == 'cst':
        switch = get_config_value('cst_serialization').lower()
    elif switch == 'default':
        switch = get_config_value('default_serialization').lower()

    if switch == 's-expression':
810
        return node.as_sxpr(flatten_threshold=get_config_value('flatten_sxpr_threshold'))
811 812
    elif switch == 'xml':
        return node.as_xml()
813 814
    elif switch == 'json':
        return node.as_json()
815 816 817 818 819 820
    elif switch == 'compact':
        return node.as_sxpr(compact=True)
    else:
        raise ValueError('Unknown serialization %s, %s' % (how, switch))


821
class FrozenNode(Node):
822 823 824 825 826 827 828 829 830 831
    """
    FrozenNode is an immutable kind of Node, i.e. it must not be changed
    after initialization. The purpose is mainly to allow certain kinds of
    optimization, like not having to instantiate empty nodes (because they
    are always the same and will be dropped while parsing, anyway).

    Frozen nodes must be used only temporarily during parsing or
    tree-transformation and should not occur in the product of the
    transformation any more. This can be verified with `tree_sanity_check()`.
    """
832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848

    def __init__(self, tag_name: str, result: ResultType) -> None:
        if isinstance(result, str) or isinstance(result, StringView):
            result = str(result)
        else:
            raise TypeError('FrozenNode only accepts string as results. '
                            '(Only leaf-nodes can be frozen nodes.)')
        super(FrozenNode, self).__init__(tag_name, result, True)

    @property
    def result(self) -> StrictResultType:
        return self._result

    @result.setter
    def result(self, result: ResultType):
        raise TypeError('FrozenNode does not allow re-assignment of results.')

eckhart's avatar
eckhart committed
849 850 851 852
    @property
    def attr(self):
        raise AssertionError("Attributes cannot be accessed on a frozen node")

Eckhart Arnold's avatar
Eckhart Arnold committed
853
    def with_pos(self, pos: int) -> 'Node':
854 855 856
        pass


857
PLACEHOLDER = FrozenNode('__PLACEHOLDER__', '')
di68kap's avatar
di68kap committed
858 859


860
def tree_sanity_check(tree: Node) -> bool:
861 862 863 864 865 866 867 868 869
    """
    Sanity check for syntax trees: One and the same node must never appear
    twice in the syntax tree. Frozen Nodes (EMTPY_NODE, PLACEHOLDER)
    should only exist temporarily and must have been dropped or eliminated
    before any kind of tree generation (i.e. parsing) or transformation
    is finished.
    :param tree: the root of the tree to be checked
    :return: True, if the tree is `sane`, False otherwise.
    """
870
    node_set = set()  # type: Set[Node]
871
    for node in tree.select(lambda nd: True, include_root=True):
872
        if node in node_set or isinstance(Node, FrozenNode):
873 874 875 876 877
            return False
        node_set.add(node)
    return True


di68kap's avatar
di68kap committed
878
class RootNode(Node):
879 880 881 882 883 884 885 886 887 888 889 890
    """The root node for the syntax tree is a special kind of node that keeps
    and manages global properties of the tree as a whole. These are first and
    foremost the list off errors that occurred during tree generation
    (i.e. parsing) or any transformation of the tree. Other properties concern
    the customization of the XML-serialization.

    The root node can be instantiated before the tree is fully parsed. This is
    necessary, because the root node is needed for managing error messages
    during the parsing process, already. In order to connect the root node to
    the tree, when parsing is finished, the swallow()-method must be called.

        errors (list):  A list of all errors that have occurred so far during
891 892
                processing (i.e. parsing, AST-transformation, compiling)
                of this tree.
di68kap's avatar
di68kap committed
893

894 895 896 897 898 899
        error_nodes (dict): A mapping of node-ids to a list of errors that
                occurred on the node with the respective id.

        error_positions (dict): A mapping of locations to a set of ids of
                nodes that contain an error at that particular location

900 901
        error_flag (int):  the highest warning or error level of all errors
                that occurred.
902 903 904 905 906 907

        inline_tags (set of strings): see `Node.as_xml()` for an explanation.

        omit_tags (set of strings): see `Node.as_xml()` for an explanation.

        empty_tags (set oif strings): see `Node.as_xml()` for an explanation.
di68kap's avatar
di68kap committed
908
    """
909

eckhart's avatar
eckhart committed
910
    def __init__(self, node: Optional[Node] = None):
911
        super().__init__('__not_yet_ready__', '')
912
        self.errors = []               # type: List[Error]
913 914
        self.error_nodes = dict()      # type: Dict[int, List[Error]]  # id(node) -> error list
        self.error_positions = dict()  # type: Dict[int, Set[int]]  # pos -> set of id(node)
di68kap's avatar
di68kap committed
915
        self.error_flag = 0
eckhart's avatar
eckhart committed
916 917
        if node is not None:
            self.swallow(node)
918
        # customization for XML-Representation
eckhart's avatar
eckhart committed
919
        self.inline_tags = set()  # type: Set[str]
920