syntaxtree.py 47 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
from typing import Callable, cast, Iterator, List, AbstractSet, Set, Union, Tuple, Optional, Dict
29

eckhart's avatar
eckhart committed
30
from DHParser.error import Error, ErrorCode, linebreaks, line_col
31
from DHParser.stringview import StringView
32
from DHParser.toolkit import get_config_value, re
di68kap's avatar
di68kap committed
33

34

di68kap's avatar
di68kap committed
35
__all__ = ('WHITESPACE_PTYPE',
36
           'TOKEN_PTYPE',
37 38
           'ZOMBIE_TAG',
           'PLACEHOLDER',
eckhart's avatar
eckhart committed
39 40 41
           'ResultType',
           'StrictResultType',
           'ChildrenType',
42
           'Node',
43
           'serialize',
44
           'FrozenNode',
45
           'tree_sanity_check',
di68kap's avatar
di68kap committed
46
           'RootNode',
47
           'parse_sxpr',
48
           'parse_xml',
eckhart's avatar
eckhart committed
49
           'parse_tree',
50 51
           'flatten_sxpr',
           'flatten_xml')
Eckhart Arnold's avatar
Eckhart Arnold committed
52 53


54 55 56 57 58 59 60 61
#######################################################################
#
# parser base and mock parsers
#
#######################################################################


WHITESPACE_PTYPE = ':Whitespace'
62
TOKEN_PTYPE = ':Token'
63

64
ZOMBIE_TAG = "__ZOMBIE__"
65

66 67 68 69 70 71 72
#######################################################################
#
# syntaxtree nodes
#
#######################################################################


73
ChildrenType = Tuple['Node', ...]
Eckhart Arnold's avatar
Eckhart Arnold committed
74
NoChildren = cast(ChildrenType, ())  # type: ChildrenType
eckhart's avatar
eckhart committed
75
StrictResultType = Union[ChildrenType, StringView, str]
76
ResultType = Union[ChildrenType, 'Node', StringView, str, None]
77 78


Eckhart Arnold's avatar
Eckhart Arnold committed
79
def flatten_sxpr(sxpr: str) -> str:
80 81
    """
    Returns S-expression ``sxpr`` as a one-liner without unnecessary
Eckhart Arnold's avatar
Eckhart Arnold committed
82 83 84
    whitespace.

    Example:
Eckhart Arnold's avatar
Eckhart Arnold committed
85
    >>> flatten_sxpr('(a\\n    (b\\n        c\\n    )\\n)\\n')
Eckhart Arnold's avatar
Eckhart Arnold committed
86 87
    '(a (b c))'
    """
88

89
    return re.sub(r'\s(?=\))', '', re.sub(r'\s+', ' ', sxpr)).strip()
Eckhart Arnold's avatar
Eckhart Arnold committed
90 91


92
def flatten_xml(xml: str) -> str:
93 94
    """
    Returns an XML-tree as a one liner without unnecessary whitespace,
95
    i.e. only whitespace within leaf-nodes is preserved.
96 97
    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`.
98
    """
99

100 101 102 103
    # works only with regex
    # return re.sub(r'\s+(?=<\w)', '', re.sub(r'(?<=</\w+>)\s+', '', xml))
    def tag_only(m):
        return m.groupdict()['closing_tag']
104
    return re.sub(r'\s+(?=<[\w:])', '', re.sub(r'(?P<closing_tag></:?\w+>)\s+', tag_only, xml))
105 106


eckhart's avatar
eckhart committed
107
RX_AMP = re.compile(r'&(?!\w+;)')
108 109


Eckhart Arnold's avatar
Eckhart Arnold committed
110
class Node:  # (collections.abc.Sized): Base class omitted for cython-compatibility
111 112 113
    """
    Represents a node in the concrete or abstract syntax tree.

114 115
    TODO: Add some documentation and doc-tests here...

116
    Attributes:
117 118
        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
119

120 121 122
        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.
123

124 125
        children (tuple):  The tuple of child nodes or an empty tuple
            if there are no child nodes. READ ONLY!
126

eckhart's avatar
eckhart committed
127 128 129 130
        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.

Eckhart Arnold's avatar
Eckhart Arnold committed
131
        parser (Parser):  The parser which generated this node.
132 133
            WARNING: In case you use mock syntax trees for testing or
            parser replacement during the AST-transformation: DO NOT
Eckhart Arnold's avatar
Eckhart Arnold committed
134 135
            rely on this being a real parser object in any phase after
            parsing (i.e. AST-transformation and compiling), for
136
            example by calling ``isinstance(node.parer, ...)``.
137

138 139 140
        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
141
            the length before AST-transformation and will never change
142
            through AST-transformation. READ ONLY!
143

144 145
        pos (int):  the position of the node within the parsed text.

Eckhart Arnold's avatar
Eckhart Arnold committed
146
            The value of ``pos`` is -1 meaning invalid by default.
147
            Setting this value will set the positions of all child
Eckhart Arnold's avatar
Eckhart Arnold committed
148
            nodes relative to this value.
149 150

            To set the pos values of all nodes in a syntax tree, the
Eckhart Arnold's avatar
Eckhart Arnold committed
151
            pos value of the root node should be set to 0 right
152 153
            after parsing.

Eckhart Arnold's avatar
Eckhart Arnold committed
154
            Other than that, this value should be considered READ ONLY.
155 156
            At any rate, it should only be reassigned during the parsing
            stage and never during or after the AST-transformation.
157

158 159
        attr (dict): An optional dictionary of XML-attr. This
            dictionary is created lazily upon first usage. The attr
160 161
            will only be shown in the XML-Representation, not in the
            S-Expression-output.
162
    """
163

164
    __slots__ = '_result', 'children', '_len', '_pos', 'tag_name', '_xml_attr'
165

166
    def __init__(self, tag_name: str, result: ResultType, leafhint: bool = False) -> None:
167 168
        """
        Initializes the ``Node``-object with the ``Parser``-Instance
169 170
        that generated the node and the parser's result.
        """
eckhart's avatar
eckhart committed
171
        self._pos = -1                  # type: int
172
        # Assignment to self.result initializes the attr _result, children and _len
di68kap's avatar
di68kap committed
173
        # The following if-clause is merely an optimization, i.e. a fast-path for leaf-Nodes
174
        if leafhint:
eckhart's avatar
eckhart committed
175
            self._result = result       # type: StrictResultType  # cast(StrictResultType, result)
176
            # self._content = None        # type: Optional[str]
177
            self.children = NoChildren  # type: ChildrenType
178
            self._len = -1              # type: int  # lazy evaluation
179 180
        else:
            self.result = result
181
        self.tag_name = tag_name        # type: str
182

eckhart's avatar
eckhart committed
183 184
    def __deepcopy__(self, memo):
        if self.children:
185
            duplicate = self.__class__(self.tag_name, copy.deepcopy(self.children), False)
eckhart's avatar
eckhart committed
186
        else:
187
            duplicate = self.__class__(self.tag_name, self.result, True)
eckhart's avatar
eckhart committed
188 189
        duplicate._pos = self._pos
        duplicate._len = self._len
eckhart's avatar
eckhart committed
190
        if self.attr_active():
di68kap's avatar
di68kap committed
191 192
            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
193
        return duplicate
Eckhart Arnold's avatar
Eckhart Arnold committed
194

195
    def __str__(self):
196 197
        if isinstance(self, RootNode):
            root = cast(RootNode, self)
198
            errors = root.errors_sorted
199 200
            if errors:
                e_pos = errors[0].pos
Eckhart Arnold's avatar
Eckhart Arnold committed
201 202
                content = self.content
                return content[:e_pos] + \
203
                   ' <<< Error on "%s" | %s >>> ' % \
Eckhart Arnold's avatar
Eckhart Arnold committed
204
                   (content[e_pos - self.pos:], '; '.join(e.message for e in errors))
205
        return self.content
Eckhart Arnold's avatar
Eckhart Arnold committed
206

207
    def __repr__(self):
208
        # mpargs = {'name': self.parser.name, 'ptype': self.parser.ptype}
209 210
        # name, ptype = (self._tag_name.split(':') + [''])[:2]
        # parg = "MockParser({name}, {ptype})".format(name=name, ptype=ptype)
211
        rarg = str(self) if not self.children else \
212
            "(" + ", ".join(child.__repr__() for child in self.children) + ")"
213
        return "Node(%s, %s)" % (self.tag_name, rarg)
214

Eckhart Arnold's avatar
Eckhart Arnold committed
215

216
    def __len__(self):
217
        if self._len < 0:
di68kap's avatar
di68kap committed
218
            self._len = sum(len(child) for child in self.children) \
219
                if self.children else len(self._result)
220 221 222 223 224 225 226 227
        return self._len


    def __bool__(self):
        # A node that is not None is always True, even if it's empty
        return True


228 229 230 231 232 233 234 235 236
    # can lead to obscure mistakes, where default object comparison behaviour is expected
    # def __eq__(self, other):
    #     """
    #     Equality of nodes: Two nodes are considered as equal, if their tag
    #     name is the same, if their results are equal and if their attributes
    #     and attribute values are the same.
    #     """
    #     return self.tag_name == other.tag_name and self.result == other.result \
    #         and self.compare_attr(other)
237

Eckhart Arnold's avatar
Eckhart Arnold committed
238

239
    def __hash__(self):
240
        return hash(self.tag_name)
241

Eckhart Arnold's avatar
Eckhart Arnold committed
242

243 244 245
    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
246
        an integer or the first child node with the given tag name. Examples::
247

248
            >>> tree = parse_sxpr('(a (b "X") (X (c "d")) (e (X "F")))')
249 250
            >>> flatten_sxpr(tree[0].as_sxpr())
            '(b "X")'
251 252
            >>> flatten_sxpr(tree["X"].as_sxpr())
            '(X (c "d"))'
253 254 255 256

        Args:
            index_or_tagname(str): Either an index of a child node or a
                tag name.
257
        Returns:
258 259
            Node: All nodes which have a given tag name.
        """
260 261 262
        if self.children:
            if isinstance(index_or_tagname, int):
                return self.children[index_or_tagname]
263
            else:
264 265 266 267 268
                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!')
269 270 271 272


    def __contains__(self, tag_name: str) -> bool:
        """
273
        Returns true if a child with the given tag name exists.
274
        Args:
275 276
            tag_name (str): tag_name which will be searched among to immediate
                descendants of this node.
277 278 279 280
        Returns:
            bool:  True, if at least one descendant node with the given tag
                name exists, False otherwise
        """
281 282 283 284 285
        # assert isinstance(tag_name, str)
        if self.children:
            for child in self.children:
                if child.tag_name == tag_name:
                    return True
286
            return False
287
        raise ValueError('Leave node cannot contain other nodes')
288 289


290
    def equals(self, other: 'Node') -> bool:
291
        """
292 293 294 295 296 297
        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`.
298 299 300 301 302 303 304 305 306 307
        """
        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


308 309 310 311 312 313 314 315 316 317 318 319 320 321
    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


322
    def is_anonymous(self) -> bool:
Eckhart Arnold's avatar
Eckhart Arnold committed
323
        return not self.tag_name or self.tag_name[0] == ':'
324

Eckhart Arnold's avatar
Eckhart Arnold committed
325

326
    @property
Eckhart Arnold's avatar
Eckhart Arnold committed
327
    def result(self) -> StrictResultType:
328 329 330 331 332
        """
        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.
        """
333 334
        return self._result

335

336
    @result.setter
Eckhart Arnold's avatar
Eckhart Arnold committed
337
    def result(self, result: ResultType):
Eckhart Arnold's avatar
Eckhart Arnold committed
338
        # # made obsolete by static type checking with mypy
Eckhart Arnold's avatar
Eckhart Arnold committed
339 340 341 342
        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
343 344
        # Possible optimization: Do not allow single nodes as argument:
        # assert not isinstance(result, Node)
345
        self._len = -1        # lazy evaluation
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
    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]
370 371

    @property
eckhart's avatar
eckhart committed
372
    def content(self) -> str:
373
        """
374 375 376
        Returns content as string. If the node has child-nodes, the
        string content of the child-nodes is recursively read and then
        concatenated.
377
        """
378 379 380 381 382 383 384 385
        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
386 387
        # return "".join(child.content for child in self.children) if self.children \
        #     else str(self._result)
di68kap's avatar
di68kap committed
388 389


390 391 392 393 394 395
    @property
    def structure(self) -> str:
        """
        Return structure (and content) as S-expression on a single line
        without any line breaks.
        """
396
        return flatten_sxpr(self.as_sxpr())
397 398


399
    @property
400
    def pos(self) -> int:
eckhart's avatar
eckhart committed
401 402
        """Returns the position of the Node's content in the source text."""
        if self._pos < 0:
Eckhart Arnold's avatar
Eckhart Arnold committed
403
            raise AssertionError("Position value not initialized! Use Node.with_pos()")
404 405
        return self._pos

eckhart's avatar
eckhart committed
406

Eckhart Arnold's avatar
Eckhart Arnold committed
407
    def with_pos(self, pos: int) -> 'Node':
eckhart's avatar
eckhart committed
408
        """
Eckhart Arnold's avatar
Eckhart Arnold committed
409
        Initialize position value. Usually, the parser guard
eckhart's avatar
eckhart committed
410 411
        (`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
412
        when Nodes are created outside the reach of the parser
eckhart's avatar
eckhart committed
413
        guard, their document-position must be assigned manually.
Eckhart Arnold's avatar
Eckhart Arnold committed
414 415
        Position values of the child nodes are assigned recursively, too.
        Returns the node itself for convenience.
eckhart's avatar
eckhart committed
416
        """
417 418 419 420
        # 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
421 422 423 424 425 426 427 428 429 430
        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
431 432
        return self

433

434 435 436 437 438 439 440 441 442 443 444 445 446
    @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
447 448 449 450 451 452 453 454 455 456 457 458 459
    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


460
    def compare_attr(self, other: 'Node') -> bool:
461
        """
462 463
        Returns True, if `self` and `other` have the same attributes with the
        same attribute values.
464
        """
465 466 467 468 469 470 471 472 473
        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
474

Eckhart Arnold's avatar
Eckhart Arnold committed
475

476
    def _tree_repr(self, tab, open_fn, close_fn, data_fn=lambda i: i,
477
                   density=0, inline=False, inline_fn=lambda node: False) -> str:
478 479 480 481 482 483 484 485
        """
        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.

486
        Args:
487
            tab (str):  The indentation string, e.g. '\t' or '    '
eckhart's avatar
eckhart committed
488
            open_fn:   (Node->str) A function that returns an opening
489
                string (e.g. an XML-tag_name) for a given node
eckhart's avatar
eckhart committed
490
            close_fn:  (Node->str) A function that returns a closeF
491
                string (e.g. an XML-tag_name) for a given node.
eckhart's avatar
eckhart committed
492
            data_fn:   (str->str) A function that filters the data string
493 494 495 496 497 498
                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
499 500
        head = open_fn(self)
        tail = close_fn(self)
501 502

        if not self.result:
503
            return head.rstrip() + tail.lstrip()
504

eckhart's avatar
eckhart committed
505
        tail = tail.lstrip(None if density & 2 else '')
506

507
        inline = inline or inline_fn(self)
508 509 510 511 512
        if inline:
            head = head.rstrip()
            tail = tail.lstrip()
            usetab, sep = '', ''
        else:
eckhart's avatar
eckhart committed
513 514
            usetab = tab if head else ''    # no indentation if tag is already omitted
            sep = '\n'
515

516 517
        if self.children:
            content = []
518
            for child in self.children:
519
                subtree = child._tree_repr(tab, open_fn, close_fn, data_fn,
520
                                           density, inline, inline_fn)
eckhart's avatar
eckhart committed
521
                if subtree:
eckhart's avatar
eckhart committed
522 523
                    st = [subtree] if inline else subtree.split('\n')
                    content.append((sep + usetab).join(s for s in st))
524
            return head + usetab + (sep + usetab).join(content) + tail
525

eckhart's avatar
eckhart committed
526
        res = self.content
eckhart's avatar
eckhart committed
527
        if not inline and not head:
eckhart's avatar
eckhart committed
528
            # strip whitespace for omitted non inline node, e.g. CharData in mixed elements
eckhart's avatar
eckhart committed
529
            res = res.strip()
530 531
        if density & 1 and res.find('\n') < 0:  # and head[0] == "<":
            # except for XML, add a gap between opening statement and content
532
            gap = ' ' if not inline and head and head.rstrip()[-1:] != '>' else ''
eckhart's avatar
eckhart committed
533
            return head.rstrip() + gap + data_fn(res) + tail.lstrip()
534
        else:
535
            return head + '\n'.join([usetab + data_fn(s) for s in res.split('\n')]) + tail
536

Eckhart Arnold's avatar
Eckhart Arnold committed
537

538 539
    def as_sxpr(self, src: str = None,
                indentation: int = 2,
540
                compact: bool = False) -> str:
541
        """
542 543
        Returns content as S-expression, i.e. in lisp-like form. If this
        method is callad on a RootNode-object,
544

545
        Args:
546 547 548
            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.
549 550
            indentation: The number of whitespaces for indentation
            compact:  If True, a compact representation is returned where
551
                brackets are omitted and only the indentation indicates the
Eckhart Arnold's avatar
Eckhart Arnold committed
552
                tree structure.
553 554
        """

eckhart's avatar
eckhart committed
555
        left_bracket, right_bracket, density = ('', '', 1) if compact else ('(', '\n)', 0)
eckhart's avatar
eckhart committed
556
        lbreaks = linebreaks(src) if src else []  # type: List[int]
557
        root = cast(RootNode, self) if isinstance(self, RootNode) else None  # type: Optional[RootNode]
558

559
        def opening(node: Node) -> str:
eckhart's avatar
eckhart committed
560
            """Returns the opening string for the representation of `node`."""
eckhart's avatar
eckhart committed
561
            txt = [left_bracket, node.tag_name]
562
            # s += " '(pos %i)" % node.add_pos
563
            # txt.append(str(id(node)))  # for debugging
eckhart's avatar
eckhart committed
564
            if node.attr_active():
565
                txt.extend(' `(%s "%s")' % (k, v) for k, v in node.attr.items())
566
            if src:
567 568
                line, col = line_col(lbreaks, node.pos)
                txt.append(" `(pos %i %i %i)" % (node.pos, line, col))
569 570
            if root and id(node) in root.error_nodes:
                txt.append(" `(err `%s)" % ' '.join(str(err) for err in root.get_errors(node)))
571
            return "".join(txt) + '\n'
572

573
        def closing(node: Node) -> str:
eckhart's avatar
eckhart committed
574 575
            """Returns the closing string for the representation of `node`."""
            return right_bracket
576

577
        def pretty(strg: str) -> str:
eckhart's avatar
eckhart committed
578 579 580 581
            """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'\"')
582

583
        return self._tree_repr(' ' * indentation, opening, closing, pretty, density=density)
Eckhart Arnold's avatar
Eckhart Arnold committed
584

eckhart's avatar
eckhart committed
585

586 587
    def as_xml(self, src: str = None,
               indentation: int = 2,
eckhart's avatar
eckhart committed
588 589 590
               inline_tags: Set[str] = set(),
               omit_tags: Set[str] = set(),
               empty_tags: Set[str] = set()) -> str:
591 592 593
        """
        Returns content as XML-tree.

594
        Args:
595 596 597
            src:  The source text or `None`. In case the source text is
                given the position will also be reported as line and
                column.
598
            indentation: The number of whitespaces for indentation
599 600 601
            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
602
                neither the opening tag nor its attr nor the closing tag. This
603 604 605
                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.
606 607
            empty_tags:  A set of tags which shall be rendered as empty elements, e.g.
                "<empty/>" instead of "<empty><empty>".
608
        """
609
        root = cast(RootNode, self) if isinstance(self, RootNode) else None  # type: Optional[RootNode]
610

611
        def opening(node: Node) -> str:
612 613 614
            """Returns the opening string for the representation of `node`."""
            if node.tag_name in omit_tags:
                return ''
eckhart's avatar
eckhart committed
615
            txt = ['<', node.tag_name]
eckhart's avatar
eckhart committed
616
            has_reserved_attrs = node.attr_active() \
eckhart's avatar
eckhart committed
617
                and any(r in node.attr for r in {'err', 'line', 'col'})
eckhart's avatar
eckhart committed
618
            if node.attr_active():
619
                txt.extend(' %s="%s"' % (k, v) for k, v in node.attr.items())
620
            if src and not has_reserved_attrs:
eckhart's avatar
eckhart committed
621
                txt.append(' line="%i" col="%i"' % line_col(line_breaks, node.pos))
622
            if root and id(node) in root.error_nodes and not has_reserved_attrs:
eckhart's avatar
eckhart committed
623
                txt.append(' err="%s"' % ''.join(str(err).replace('"', r'\"')
eckhart's avatar
eckhart committed
624
                                                 for err in root.get_errors(node)))
625 626 627
            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
628
                ending = "/>\n" if not node.tag_name[0] == '?' else "?>\n"
629 630 631
            else:
                ending = ">\n"
            return "".join(txt + [ending])
632

633
        def closing(node: Node):
634
            """Returns the closing string for the representation of `node`."""
635
            if node.tag_name in omit_tags or node.tag_name in empty_tags:
636
                return ''
637
            return ('\n</') + node.tag_name + '>'
638

639 640 641 642 643 644
        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

645
        def inlining(node: Node):
646 647 648 649
            """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
650
            return node.tag_name in inline_tags \
eckhart's avatar
eckhart committed
651
                or (node.attr_active()
eckhart's avatar
eckhart committed
652
                    and node.attr.get('xml:space', 'default') == 'preserve')
653

654
        line_breaks = linebreaks(src) if src else []
655
        return self._tree_repr(' ' * indentation, opening, closing, sanitizer,
656
                               density=1, inline_fn=inlining)
657

Eckhart Arnold's avatar
Eckhart Arnold committed
658

eckhart's avatar
eckhart committed
659
    def select(self, match_function: Callable, include_root: bool = False, reverse: bool = False) \
660
            -> Iterator['Node']:
eckhart's avatar
eckhart committed
661
        """
662
        Finds nodes in the tree that fulfill a given criterion.
eckhart's avatar
eckhart committed
663

664
        `select` is a generator that yields all nodes for which the
di68kap's avatar
di68kap committed
665
        given `match_function` evaluates to True. The tree is
666 667 668
        traversed pre-order.

        See function `Node.select_by_tag` for some examples.
eckhart's avatar
eckhart committed
669

670 671 672
        Args:
            match_function (function): A function  that takes as Node
                object as argument and returns True or False
673 674
            include_root (bool): If False, only descendant nodes will be
                checked for a match.
675 676
            reverse (bool): If True, the tree will be walked in reverse
                order, i.e. last children first.
677
        Yields:
678
            Node: All nodes of the tree for which
679 680
            ``match_function(node)`` returns True
        """
681
        if include_root and match_function(self):
682
            yield self
683 684 685
        child_iterator = reversed(self.children) if reverse else self.children
        for child in child_iterator:
            for node in child.select(match_function, True, reverse):
eckhart's avatar
eckhart committed
686
                yield node
687

Eckhart Arnold's avatar
Eckhart Arnold committed
688

eckhart's avatar
eckhart committed
689
    def select_by_tag(self, tag_names: Union[str, AbstractSet[str]],
eckhart's avatar
eckhart committed
690
                      include_root: bool = False) -> Iterator['Node']:
691
        """
692 693 694 695
        Returns an iterator that runs through all descendants that have one
        of the given tag names.

        Examples::
696

697
            >>> tree = parse_sxpr('(a (b "X") (X (c "d")) (e (X "F")))')
698
            >>> list(flatten_sxpr(item.as_sxpr()) for item in tree.select_by_tag("X", False))
699
            ['(X (c "d"))', '(X "F")']
700
            >>> list(flatten_sxpr(item.as_sxpr()) for item in tree.select_by_tag({"X", "b"}, False))
701
            ['(b "X")', '(X (c "d"))', '(X "F")']
702
            >>> any(tree.select_by_tag('a', False))
703
            False
704
            >>> list(flatten_sxpr(item.as_sxpr()) for item in tree.select_by_tag('a', True))
705
            ['(a (b "X") (X (c "d")) (e (X "F")))']
706 707
            >>> flatten_sxpr(next(tree.select_by_tag("X", False)).as_sxpr())
            '(X (c "d"))'
708 709

        Args:
710 711 712 713
            tag_name(set): A tag name or set of tag names that is being
                searched for
            include_root (bool): If False, only descendant nodes will be
                checked for a match.
714 715 716
        Yields:
            Node: All nodes which have a given tag name.
        """
717
        if isinstance(tag_names, str):
eckhart's avatar
eckhart committed
718
            tag_names = frozenset({tag_names})
719
        return self.select(lambda node: node.tag_name in tag_names, include_root)
720 721


722 723 724 725
    def pick(self, tag_names: Union[str, Set[str]]) -> Optional['Node']:
        """
        Picks the first descendant with one of the given tag_names.

726
        This function is mostly just syntactic sugar for
727 728 729 730 731 732 733 734 735 736
        ``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


737
    def tree_size(self) -> int:
eckhart's avatar
eckhart committed
738 739 740
        """
        Recursively counts the number of nodes in the tree including the root node.
        """
741 742 743
        return sum(child.tree_size() for child in self.children) + 1


744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770
def serialize(node: Node, how: str='default') -> str:
    """
    Serializes the tree starting with `node` either as S-expression, XML
    or in compact form. Possible values for `how` are 'S-expression',
    'XML', 'compact' accordingly, or 'AST', 'CST', 'default' in which case
    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':
        return node.as_sxpr()
    elif switch == 'xml':
        return node.as_xml()
    elif switch == 'compact':
        return node.as_sxpr(compact=True)
    else:
        raise ValueError('Unknown serialization %s, %s' % (how, switch))


771
class FrozenNode(Node):
772 773 774 775 776 777 778 779 780 781
    """
    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()`.
    """
782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798

    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
799 800 801 802
    @property
    def attr(self):
        raise AssertionError("Attributes cannot be accessed on a frozen node")

Eckhart Arnold's avatar
Eckhart Arnold committed
803
    def with_pos(self, pos: int) -> 'Node':
804 805 806
        pass


807
PLACEHOLDER = FrozenNode('__PLACEHOLDER__', '')
di68kap's avatar
di68kap committed
808 809


810
def tree_sanity_check(tree: Node) -> bool:
811 812 813 814 815 816 817 818 819
    """
    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.
    """
820
    node_set = set()  # type: Set[Node]
821
    for node in tree.select(lambda nd: True, include_root=True):
822
        if node in node_set or isinstance(Node, FrozenNode):
823 824 825 826 827
            return False
        node_set.add(node)
    return True


di68kap's avatar
di68kap committed
828
class RootNode(Node):
829 830 831 832 833 834 835 836 837 838 839 840
    """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
841 842
                processing (i.e. parsing, AST-transformation, compiling)
                of this tree.
di68kap's avatar
di68kap committed
843

844 845 846 847 848 849
        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

850 851
        error_flag (int):  the highest warning or error level of all errors
                that occurred.
852 853 854 855 856 857

        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
858
    """
859

eckhart's avatar
eckhart committed
860
    def __init__(self, node: Optional[Node] = None):
861
        super().__init__('__not_yet_ready__', '')
862
        self.errors = []               # type: List[Error]
863 864
        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
865
        self.error_flag = 0
eckhart's avatar
eckhart committed
866 867
        if node is not None:
            self.swallow(node)
868
        # customization for XML-Representation
eckhart's avatar
eckhart committed
869
        self.inline_tags = set()  # type: Set[str]