2 # The following YAML grammar is LL(1) and is parsed by a recursive descent
5 # stream ::= STREAM-START implicit_document? explicit_document* STREAM-END
6 # implicit_document ::= block_node DOCUMENT-END*
7 # explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
8 # block_node_or_indentless_sequence ::=
10 # | properties (block_content | indentless_block_sequence)?
12 # | indentless_block_sequence
13 # block_node ::= ALIAS
14 # | properties block_content?
17 # | properties flow_content?
19 # properties ::= TAG ANCHOR? | ANCHOR TAG?
20 # block_content ::= block_collection | flow_collection | SCALAR
21 # flow_content ::= flow_collection | SCALAR
22 # block_collection ::= block_sequence | block_mapping
23 # flow_collection ::= flow_sequence | flow_mapping
24 # block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
25 # indentless_sequence ::= (BLOCK-ENTRY block_node?)+
26 # block_mapping ::= BLOCK-MAPPING_START
27 # ((KEY block_node_or_indentless_sequence?)?
28 # (VALUE block_node_or_indentless_sequence?)?)*
30 # flow_sequence ::= FLOW-SEQUENCE-START
31 # (flow_sequence_entry FLOW-ENTRY)*
32 # flow_sequence_entry?
34 # flow_sequence_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
35 # flow_mapping ::= FLOW-MAPPING-START
36 # (flow_mapping_entry FLOW-ENTRY)*
39 # flow_mapping_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
43 # stream: { STREAM-START }
44 # explicit_document: { DIRECTIVE DOCUMENT-START }
45 # implicit_document: FIRST(block_node)
46 # block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START }
47 # flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START }
48 # block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
49 # flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
50 # block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START }
51 # flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
52 # block_sequence: { BLOCK-SEQUENCE-START }
53 # block_mapping: { BLOCK-MAPPING-START }
54 # block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY }
55 # indentless_sequence: { ENTRY }
56 # flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
57 # flow_sequence: { FLOW-SEQUENCE-START }
58 # flow_mapping: { FLOW-MAPPING-START }
59 # flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
60 # flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
62 __all__
= ['Parser', 'ParserError']
64 from error
import MarkedYAMLError
69 class ParserError(MarkedYAMLError
):
73 # Since writing a recursive-descendant parser is a straightforward task, we
74 # do not give many comments here.
75 # Note that we use Python generators. If you rewrite the parser in another
76 # language, you may replace all 'yield'-s with event handler calls.
80 u
'!!': u
'tag:yaml.org,2002:',
84 self
.current_event
= None
85 self
.yaml_version
= None
89 self
.state
= self
.parse_stream_start
91 def check_event(self
, *choices
):
92 # Check the type of the next event.
93 if self
.current_event
is None:
95 self
.current_event
= self
.state()
96 if self
.current_event
is not None:
99 for choice
in choices
:
100 if isinstance(self
.current_event
, choice
):
104 def peek_event(self
):
105 # Get the next event.
106 if self
.current_event
is None:
108 self
.current_event
= self
.state()
109 return self
.current_event
112 # Get the next event and proceed further.
113 if self
.current_event
is None:
115 self
.current_event
= self
.state()
116 value
= self
.current_event
117 self
.current_event
= None
120 # stream ::= STREAM-START implicit_document? explicit_document* STREAM-END
121 # implicit_document ::= block_node DOCUMENT-END*
122 # explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
124 def parse_stream_start(self
):
126 # Parse the stream start.
127 token
= self
.get_token()
128 event
= StreamStartEvent(token
.start_mark
, token
.end_mark
,
129 encoding
=token
.encoding
)
131 # Prepare the next state.
132 self
.state
= self
.parse_implicit_document_start
136 def parse_implicit_document_start(self
):
138 # Parse an implicit document.
139 if not self
.check_token(DirectiveToken
, DocumentStartToken
,
141 self
.tag_handles
= self
.DEFAULT_TAGS
142 token
= self
.peek_token()
143 start_mark
= end_mark
= token
.start_mark
144 event
= DocumentStartEvent(start_mark
, end_mark
,
147 # Prepare the next state.
148 self
.states
.append(self
.parse_document_end
)
149 self
.state
= self
.parse_block_node
154 return self
.parse_document_start()
156 def parse_document_start(self
):
158 # Parse an explicit document.
159 if not self
.check_token(StreamEndToken
):
160 token
= self
.peek_token()
161 start_mark
= token
.start_mark
162 version
, tags
= self
.process_directives()
163 if not self
.check_token(DocumentStartToken
):
164 raise ParserError(None, None,
165 "expected '<document start>', but found %r"
166 % self
.peek_token().id,
167 self
.peek_token().start_mark
)
168 token
= self
.get_token()
169 end_mark
= token
.end_mark
170 event
= DocumentStartEvent(start_mark
, end_mark
,
171 explicit
=True, version
=version
, tags
=tags
)
172 self
.states
.append(self
.parse_document_end
)
173 self
.state
= self
.parse_document_content
175 # Parse the end of the stream.
176 token
= self
.get_token()
177 event
= StreamEndEvent(token
.start_mark
, token
.end_mark
)
178 assert not self
.states
179 assert not self
.marks
183 def parse_document_end(self
):
185 # Parse the document end.
186 token
= self
.peek_token()
187 start_mark
= end_mark
= token
.start_mark
189 while self
.check_token(DocumentEndToken
):
190 token
= self
.get_token()
191 end_mark
= token
.end_mark
193 event
= DocumentEndEvent(start_mark
, end_mark
,
196 # Prepare the next state.
197 self
.state
= self
.parse_document_start
201 def parse_document_content(self
):
202 if self
.check_token(DirectiveToken
,
203 DocumentStartToken
, DocumentEndToken
, StreamEndToken
):
204 event
= self
.process_empty_scalar(self
.peek_token().start_mark
)
205 self
.state
= self
.states
.pop()
208 return self
.parse_block_node()
210 def process_directives(self
):
211 self
.yaml_version
= None
212 self
.tag_handles
= {}
213 while self
.check_token(DirectiveToken
):
214 token
= self
.get_token()
215 if token
.name
== u
'YAML':
216 if self
.yaml_version
is not None:
217 raise ParserError(None, None,
218 "found duplicate YAML directive", token
.start_mark
)
219 major
, minor
= token
.value
221 raise ParserError(None, None,
222 "found incompatible YAML document (version 1.* is required)",
224 self
.yaml_version
= token
.value
225 elif token
.name
== u
'TAG':
226 handle
, prefix
= token
.value
227 if handle
in self
.tag_handles
:
228 raise ParserError(None, None,
229 "duplicate tag handle %r" % handle
.encode('utf-8'),
231 self
.tag_handles
[handle
] = prefix
233 value
= self
.yaml_version
, self
.tag_handles
.copy()
235 value
= self
.yaml_version
, None
236 for key
in self
.DEFAULT_TAGS
:
237 if key
not in self
.tag_handles
:
238 self
.tag_handles
[key
] = self
.DEFAULT_TAGS
[key
]
241 # block_node_or_indentless_sequence ::= ALIAS
242 # | properties (block_content | indentless_block_sequence)?
244 # | indentless_block_sequence
245 # block_node ::= ALIAS
246 # | properties block_content?
248 # flow_node ::= ALIAS
249 # | properties flow_content?
251 # properties ::= TAG ANCHOR? | ANCHOR TAG?
252 # block_content ::= block_collection | flow_collection | SCALAR
253 # flow_content ::= flow_collection | SCALAR
254 # block_collection ::= block_sequence | block_mapping
255 # flow_collection ::= flow_sequence | flow_mapping
257 def parse_block_node(self
):
258 return self
.parse_node(block
=True)
260 def parse_flow_node(self
):
261 return self
.parse_node()
263 def parse_block_node_or_indentless_sequence(self
):
264 return self
.parse_node(block
=True, indentless_sequence
=True)
266 def parse_node(self
, block
=False, indentless_sequence
=False):
267 if self
.check_token(AliasToken
):
268 token
= self
.get_token()
269 event
= AliasEvent(token
.value
, token
.start_mark
, token
.end_mark
)
270 self
.state
= self
.states
.pop()
274 start_mark
= end_mark
= tag_mark
= None
275 if self
.check_token(AnchorToken
):
276 token
= self
.get_token()
277 start_mark
= token
.start_mark
278 end_mark
= token
.end_mark
280 if self
.check_token(TagToken
):
281 token
= self
.get_token()
282 tag_mark
= token
.start_mark
283 end_mark
= token
.end_mark
285 elif self
.check_token(TagToken
):
286 token
= self
.get_token()
287 start_mark
= tag_mark
= token
.start_mark
288 end_mark
= token
.end_mark
290 if self
.check_token(AnchorToken
):
291 token
= self
.get_token()
292 end_mark
= token
.end_mark
294 if tag
is not None and tag
!= u
'!':
296 if handle
is not None:
297 if handle
not in self
.tag_handles
:
298 raise ParserError("while parsing a node", start_mark
,
299 "found undefined tag handle %r" % handle
.encode('utf-8'),
301 tag
= self
.tag_handles
[handle
]+suffix
305 # raise ParserError("while parsing a node", start_mark,
306 # "found non-specific tag '!'", tag_mark,
307 # "Please check 'http://pyyaml.org/wiki/YAMLNonSpecificTag' and share your opinion.")
308 if start_mark
is None:
309 start_mark
= end_mark
= self
.peek_token().start_mark
311 implicit
= (tag
is None or tag
== u
'!')
312 if indentless_sequence
and self
.check_token(BlockEntryToken
):
313 end_mark
= self
.peek_token().end_mark
314 event
= SequenceStartEvent(anchor
, tag
, implicit
,
315 start_mark
, end_mark
)
316 self
.state
= self
.parse_indentless_sequence_entry
318 if self
.check_token(ScalarToken
):
319 token
= self
.get_token()
320 end_mark
= token
.end_mark
321 if (token
.plain
and tag
is None) or tag
== u
'!':
322 implicit
= (True, False)
324 implicit
= (False, True)
326 implicit
= (False, False)
327 event
= ScalarEvent(anchor
, tag
, implicit
, token
.value
,
328 start_mark
, end_mark
, style
=token
.style
)
329 self
.state
= self
.states
.pop()
330 elif self
.check_token(FlowSequenceStartToken
):
331 end_mark
= self
.peek_token().end_mark
332 event
= SequenceStartEvent(anchor
, tag
, implicit
,
333 start_mark
, end_mark
, flow_style
=True)
334 self
.state
= self
.parse_flow_sequence_first_entry
335 elif self
.check_token(FlowMappingStartToken
):
336 end_mark
= self
.peek_token().end_mark
337 event
= MappingStartEvent(anchor
, tag
, implicit
,
338 start_mark
, end_mark
, flow_style
=True)
339 self
.state
= self
.parse_flow_mapping_first_key
340 elif block
and self
.check_token(BlockSequenceStartToken
):
341 end_mark
= self
.peek_token().start_mark
342 event
= SequenceStartEvent(anchor
, tag
, implicit
,
343 start_mark
, end_mark
, flow_style
=False)
344 self
.state
= self
.parse_block_sequence_first_entry
345 elif block
and self
.check_token(BlockMappingStartToken
):
346 end_mark
= self
.peek_token().start_mark
347 event
= MappingStartEvent(anchor
, tag
, implicit
,
348 start_mark
, end_mark
, flow_style
=False)
349 self
.state
= self
.parse_block_mapping_first_key
350 elif anchor
is not None or tag
is not None:
351 # Empty scalars are allowed even if a tag or an anchor is
353 event
= ScalarEvent(anchor
, tag
, (implicit
, False), u
'',
354 start_mark
, end_mark
)
355 self
.state
= self
.states
.pop()
361 token
= self
.peek_token()
362 raise ParserError("while parsing a %s node" % node
, start_mark
,
363 "expected the node content, but found %r" % token
.id,
367 # block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
369 def parse_block_sequence_first_entry(self
):
370 token
= self
.get_token()
371 self
.marks
.append(token
.start_mark
)
372 return self
.parse_block_sequence_entry()
374 def parse_block_sequence_entry(self
):
375 if self
.check_token(BlockEntryToken
):
376 token
= self
.get_token()
377 if not self
.check_token(BlockEntryToken
, BlockEndToken
):
378 self
.states
.append(self
.parse_block_sequence_entry
)
379 return self
.parse_block_node()
381 self
.state
= self
.parse_block_sequence_entry
382 return self
.process_empty_scalar(token
.end_mark
)
383 if not self
.check_token(BlockEndToken
):
384 token
= self
.peek_token()
385 raise ParserError("while parsing a block collection", self
.marks
[-1],
386 "expected <block end>, but found %r" % token
.id, token
.start_mark
)
387 token
= self
.get_token()
388 event
= SequenceEndEvent(token
.start_mark
, token
.end_mark
)
389 self
.state
= self
.states
.pop()
393 # indentless_sequence ::= (BLOCK-ENTRY block_node?)+
395 def parse_indentless_sequence_entry(self
):
396 if self
.check_token(BlockEntryToken
):
397 token
= self
.get_token()
398 if not self
.check_token(BlockEntryToken
,
399 KeyToken
, ValueToken
, BlockEndToken
):
400 self
.states
.append(self
.parse_indentless_sequence_entry
)
401 return self
.parse_block_node()
403 self
.state
= self
.parse_indentless_sequence_entry
404 return self
.process_empty_scalar(token
.end_mark
)
405 token
= self
.peek_token()
406 event
= SequenceEndEvent(token
.start_mark
, token
.start_mark
)
407 self
.state
= self
.states
.pop()
410 # block_mapping ::= BLOCK-MAPPING_START
411 # ((KEY block_node_or_indentless_sequence?)?
412 # (VALUE block_node_or_indentless_sequence?)?)*
415 def parse_block_mapping_first_key(self
):
416 token
= self
.get_token()
417 self
.marks
.append(token
.start_mark
)
418 return self
.parse_block_mapping_key()
420 def parse_block_mapping_key(self
):
421 if self
.check_token(KeyToken
):
422 token
= self
.get_token()
423 if not self
.check_token(KeyToken
, ValueToken
, BlockEndToken
):
424 self
.states
.append(self
.parse_block_mapping_value
)
425 return self
.parse_block_node_or_indentless_sequence()
427 self
.state
= self
.parse_block_mapping_value
428 return self
.process_empty_scalar(token
.end_mark
)
429 if not self
.check_token(BlockEndToken
):
430 token
= self
.peek_token()
431 raise ParserError("while parsing a block mapping", self
.marks
[-1],
432 "expected <block end>, but found %r" % token
.id, token
.start_mark
)
433 token
= self
.get_token()
434 event
= MappingEndEvent(token
.start_mark
, token
.end_mark
)
435 self
.state
= self
.states
.pop()
439 def parse_block_mapping_value(self
):
440 if self
.check_token(ValueToken
):
441 token
= self
.get_token()
442 if not self
.check_token(KeyToken
, ValueToken
, BlockEndToken
):
443 self
.states
.append(self
.parse_block_mapping_key
)
444 return self
.parse_block_node_or_indentless_sequence()
446 self
.state
= self
.parse_block_mapping_key
447 return self
.process_empty_scalar(token
.end_mark
)
449 self
.state
= self
.parse_block_mapping_key
450 token
= self
.peek_token()
451 return self
.process_empty_scalar(token
.start_mark
)
453 # flow_sequence ::= FLOW-SEQUENCE-START
454 # (flow_sequence_entry FLOW-ENTRY)*
455 # flow_sequence_entry?
457 # flow_sequence_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
459 # Note that while production rules for both flow_sequence_entry and
460 # flow_mapping_entry are equal, their interpretations are different.
461 # For `flow_sequence_entry`, the part `KEY flow_node? (VALUE flow_node?)?`
462 # generate an inline mapping (set syntax).
464 def parse_flow_sequence_first_entry(self
):
465 token
= self
.get_token()
466 self
.marks
.append(token
.start_mark
)
467 return self
.parse_flow_sequence_entry(first
=True)
469 def parse_flow_sequence_entry(self
, first
=False):
470 if not self
.check_token(FlowSequenceEndToken
):
472 if self
.check_token(FlowEntryToken
):
475 token
= self
.peek_token()
476 raise ParserError("while parsing a flow sequence", self
.marks
[-1],
477 "expected ',' or ']', but got %r" % token
.id, token
.start_mark
)
479 if self
.check_token(KeyToken
):
480 token
= self
.peek_token()
481 event
= MappingStartEvent(None, None, True,
482 token
.start_mark
, token
.end_mark
,
484 self
.state
= self
.parse_flow_sequence_entry_mapping_key
486 elif not self
.check_token(FlowSequenceEndToken
):
487 self
.states
.append(self
.parse_flow_sequence_entry
)
488 return self
.parse_flow_node()
489 token
= self
.get_token()
490 event
= SequenceEndEvent(token
.start_mark
, token
.end_mark
)
491 self
.state
= self
.states
.pop()
495 def parse_flow_sequence_entry_mapping_key(self
):
496 token
= self
.get_token()
497 if not self
.check_token(ValueToken
,
498 FlowEntryToken
, FlowSequenceEndToken
):
499 self
.states
.append(self
.parse_flow_sequence_entry_mapping_value
)
500 return self
.parse_flow_node()
502 self
.state
= self
.parse_flow_sequence_entry_mapping_value
503 return self
.process_empty_scalar(token
.end_mark
)
505 def parse_flow_sequence_entry_mapping_value(self
):
506 if self
.check_token(ValueToken
):
507 token
= self
.get_token()
508 if not self
.check_token(FlowEntryToken
, FlowSequenceEndToken
):
509 self
.states
.append(self
.parse_flow_sequence_entry_mapping_end
)
510 return self
.parse_flow_node()
512 self
.state
= self
.parse_flow_sequence_entry_mapping_end
513 return self
.process_empty_scalar(token
.end_mark
)
515 self
.state
= self
.parse_flow_sequence_entry_mapping_end
516 token
= self
.peek_token()
517 return self
.process_empty_scalar(token
.start_mark
)
519 def parse_flow_sequence_entry_mapping_end(self
):
520 self
.state
= self
.parse_flow_sequence_entry
521 token
= self
.peek_token()
522 return MappingEndEvent(token
.start_mark
, token
.start_mark
)
524 # flow_mapping ::= FLOW-MAPPING-START
525 # (flow_mapping_entry FLOW-ENTRY)*
526 # flow_mapping_entry?
528 # flow_mapping_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
530 def parse_flow_mapping_first_key(self
):
531 token
= self
.get_token()
532 self
.marks
.append(token
.start_mark
)
533 return self
.parse_flow_mapping_key(first
=True)
535 def parse_flow_mapping_key(self
, first
=False):
536 if not self
.check_token(FlowMappingEndToken
):
538 if self
.check_token(FlowEntryToken
):
541 token
= self
.peek_token()
542 raise ParserError("while parsing a flow mapping", self
.marks
[-1],
543 "expected ',' or '}', but got %r" % token
.id, token
.start_mark
)
544 if self
.check_token(KeyToken
):
545 token
= self
.get_token()
546 if not self
.check_token(ValueToken
,
547 FlowEntryToken
, FlowMappingEndToken
):
548 self
.states
.append(self
.parse_flow_mapping_value
)
549 return self
.parse_flow_node()
551 self
.state
= self
.parse_flow_mapping_value
552 return self
.process_empty_scalar(token
.end_mark
)
553 elif not self
.check_token(FlowMappingEndToken
):
554 self
.states
.append(self
.parse_flow_mapping_empty_value
)
555 return self
.parse_flow_node()
556 token
= self
.get_token()
557 event
= MappingEndEvent(token
.start_mark
, token
.end_mark
)
558 self
.state
= self
.states
.pop()
562 def parse_flow_mapping_value(self
):
563 if self
.check_token(ValueToken
):
564 token
= self
.get_token()
565 if not self
.check_token(FlowEntryToken
, FlowMappingEndToken
):
566 self
.states
.append(self
.parse_flow_mapping_key
)
567 return self
.parse_flow_node()
569 self
.state
= self
.parse_flow_mapping_key
570 return self
.process_empty_scalar(token
.end_mark
)
572 self
.state
= self
.parse_flow_mapping_key
573 token
= self
.peek_token()
574 return self
.process_empty_scalar(token
.start_mark
)
576 def parse_flow_mapping_empty_value(self
):
577 self
.state
= self
.parse_flow_mapping_key
578 return self
.process_empty_scalar(self
.peek_token().start_mark
)
580 def process_empty_scalar(self
, mark
):
581 return ScalarEvent(None, None, (True, False), u
'', mark
, mark
)