590 lines
25 KiB
Python
590 lines
25 KiB
Python
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# The following YAML grammar is LL(1) and is parsed by a recursive descent
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# parser.
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#
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# stream ::= STREAM-START implicit_document? explicit_document* STREAM-END
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# implicit_document ::= block_node DOCUMENT-END*
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# explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
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# block_node_or_indentless_sequence ::=
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# ALIAS
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# | properties (block_content | indentless_block_sequence)?
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# | block_content
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# | indentless_block_sequence
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# block_node ::= ALIAS
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# | properties block_content?
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# | block_content
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# flow_node ::= ALIAS
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# | properties flow_content?
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# | flow_content
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# properties ::= TAG ANCHOR? | ANCHOR TAG?
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# block_content ::= block_collection | flow_collection | SCALAR
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# flow_content ::= flow_collection | SCALAR
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# block_collection ::= block_sequence | block_mapping
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# flow_collection ::= flow_sequence | flow_mapping
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# block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
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# indentless_sequence ::= (BLOCK-ENTRY block_node?)+
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# block_mapping ::= BLOCK-MAPPING_START
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# ((KEY block_node_or_indentless_sequence?)?
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# (VALUE block_node_or_indentless_sequence?)?)*
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# BLOCK-END
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# flow_sequence ::= FLOW-SEQUENCE-START
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# (flow_sequence_entry FLOW-ENTRY)*
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# flow_sequence_entry?
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# FLOW-SEQUENCE-END
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# flow_sequence_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
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# flow_mapping ::= FLOW-MAPPING-START
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# (flow_mapping_entry FLOW-ENTRY)*
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# flow_mapping_entry?
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# FLOW-MAPPING-END
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# flow_mapping_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
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#
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# FIRST sets:
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#
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# stream: { STREAM-START }
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# explicit_document: { DIRECTIVE DOCUMENT-START }
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# implicit_document: FIRST(block_node)
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# block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START }
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# flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START }
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# block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
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# flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
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# block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START }
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# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
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# block_sequence: { BLOCK-SEQUENCE-START }
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# block_mapping: { BLOCK-MAPPING-START }
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# block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY }
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# indentless_sequence: { ENTRY }
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# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
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# flow_sequence: { FLOW-SEQUENCE-START }
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# flow_mapping: { FLOW-MAPPING-START }
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# flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
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# flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
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__all__ = ['Parser', 'ParserError']
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from .error import MarkedYAMLError
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from .tokens import *
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from .events import *
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from .scanner import *
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class ParserError(MarkedYAMLError):
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pass
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class Parser:
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# Since writing a recursive-descendant parser is a straightforward task, we
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# do not give many comments here.
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DEFAULT_TAGS = {
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'!': '!',
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'!!': 'tag:yaml.org,2002:',
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}
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def __init__(self):
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self.current_event = None
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self.yaml_version = None
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self.tag_handles = {}
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self.states = []
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self.marks = []
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self.state = self.parse_stream_start
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def dispose(self):
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# Reset the state attributes (to clear self-references)
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self.states = []
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self.state = None
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def check_event(self, *choices):
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# Check the type of the next event.
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if self.current_event is None:
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if self.state:
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self.current_event = self.state()
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if self.current_event is not None:
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if not choices:
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return True
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for choice in choices:
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if isinstance(self.current_event, choice):
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return True
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return False
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def peek_event(self):
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# Get the next event.
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if self.current_event is None:
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if self.state:
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self.current_event = self.state()
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return self.current_event
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def get_event(self):
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# Get the next event and proceed further.
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if self.current_event is None:
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if self.state:
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self.current_event = self.state()
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value = self.current_event
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self.current_event = None
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return value
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# stream ::= STREAM-START implicit_document? explicit_document* STREAM-END
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# implicit_document ::= block_node DOCUMENT-END*
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# explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
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def parse_stream_start(self):
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# Parse the stream start.
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token = self.get_token()
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event = StreamStartEvent(token.start_mark, token.end_mark,
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encoding=token.encoding)
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# Prepare the next state.
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self.state = self.parse_implicit_document_start
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return event
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def parse_implicit_document_start(self):
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# Parse an implicit document.
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if not self.check_token(DirectiveToken, DocumentStartToken,
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StreamEndToken):
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self.tag_handles = self.DEFAULT_TAGS
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token = self.peek_token()
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start_mark = end_mark = token.start_mark
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event = DocumentStartEvent(start_mark, end_mark,
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explicit=False)
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# Prepare the next state.
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self.states.append(self.parse_document_end)
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self.state = self.parse_block_node
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return event
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else:
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return self.parse_document_start()
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def parse_document_start(self):
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# Parse any extra document end indicators.
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while self.check_token(DocumentEndToken):
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self.get_token()
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# Parse an explicit document.
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if not self.check_token(StreamEndToken):
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token = self.peek_token()
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start_mark = token.start_mark
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version, tags = self.process_directives()
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if not self.check_token(DocumentStartToken):
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raise ParserError(None, None,
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"expected '<document start>', but found %r"
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% self.peek_token().id,
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self.peek_token().start_mark)
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token = self.get_token()
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end_mark = token.end_mark
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event = DocumentStartEvent(start_mark, end_mark,
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explicit=True, version=version, tags=tags)
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self.states.append(self.parse_document_end)
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self.state = self.parse_document_content
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else:
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# Parse the end of the stream.
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token = self.get_token()
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event = StreamEndEvent(token.start_mark, token.end_mark)
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assert not self.states
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assert not self.marks
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self.state = None
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return event
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def parse_document_end(self):
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# Parse the document end.
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token = self.peek_token()
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start_mark = end_mark = token.start_mark
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explicit = False
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if self.check_token(DocumentEndToken):
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token = self.get_token()
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end_mark = token.end_mark
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explicit = True
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event = DocumentEndEvent(start_mark, end_mark,
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explicit=explicit)
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# Prepare the next state.
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self.state = self.parse_document_start
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return event
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def parse_document_content(self):
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if self.check_token(DirectiveToken,
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DocumentStartToken, DocumentEndToken, StreamEndToken):
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event = self.process_empty_scalar(self.peek_token().start_mark)
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self.state = self.states.pop()
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return event
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else:
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return self.parse_block_node()
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def process_directives(self):
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self.yaml_version = None
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self.tag_handles = {}
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while self.check_token(DirectiveToken):
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token = self.get_token()
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if token.name == 'YAML':
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if self.yaml_version is not None:
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raise ParserError(None, None,
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"found duplicate YAML directive", token.start_mark)
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major, minor = token.value
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if major != 1:
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raise ParserError(None, None,
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"found incompatible YAML document (version 1.* is required)",
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token.start_mark)
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self.yaml_version = token.value
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elif token.name == 'TAG':
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handle, prefix = token.value
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if handle in self.tag_handles:
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raise ParserError(None, None,
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"duplicate tag handle %r" % handle,
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token.start_mark)
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self.tag_handles[handle] = prefix
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if self.tag_handles:
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value = self.yaml_version, self.tag_handles.copy()
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else:
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value = self.yaml_version, None
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for key in self.DEFAULT_TAGS:
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if key not in self.tag_handles:
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self.tag_handles[key] = self.DEFAULT_TAGS[key]
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return value
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# block_node_or_indentless_sequence ::= ALIAS
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# | properties (block_content | indentless_block_sequence)?
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# | block_content
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# | indentless_block_sequence
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# block_node ::= ALIAS
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# | properties block_content?
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# | block_content
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# flow_node ::= ALIAS
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# | properties flow_content?
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# | flow_content
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# properties ::= TAG ANCHOR? | ANCHOR TAG?
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# block_content ::= block_collection | flow_collection | SCALAR
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# flow_content ::= flow_collection | SCALAR
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# block_collection ::= block_sequence | block_mapping
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# flow_collection ::= flow_sequence | flow_mapping
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def parse_block_node(self):
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return self.parse_node(block=True)
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def parse_flow_node(self):
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return self.parse_node()
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def parse_block_node_or_indentless_sequence(self):
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return self.parse_node(block=True, indentless_sequence=True)
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def parse_node(self, block=False, indentless_sequence=False):
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if self.check_token(AliasToken):
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token = self.get_token()
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event = AliasEvent(token.value, token.start_mark, token.end_mark)
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self.state = self.states.pop()
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else:
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anchor = None
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tag = None
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start_mark = end_mark = tag_mark = None
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if self.check_token(AnchorToken):
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token = self.get_token()
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start_mark = token.start_mark
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end_mark = token.end_mark
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anchor = token.value
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if self.check_token(TagToken):
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token = self.get_token()
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tag_mark = token.start_mark
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end_mark = token.end_mark
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tag = token.value
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elif self.check_token(TagToken):
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token = self.get_token()
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start_mark = tag_mark = token.start_mark
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end_mark = token.end_mark
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tag = token.value
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if self.check_token(AnchorToken):
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token = self.get_token()
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end_mark = token.end_mark
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anchor = token.value
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if tag is not None:
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handle, suffix = tag
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if handle is not None:
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if handle not in self.tag_handles:
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raise ParserError("while parsing a node", start_mark,
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"found undefined tag handle %r" % handle,
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tag_mark)
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tag = self.tag_handles[handle]+suffix
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else:
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tag = suffix
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#if tag == '!':
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# raise ParserError("while parsing a node", start_mark,
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# "found non-specific tag '!'", tag_mark,
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# "Please check 'http://pyyaml.org/wiki/YAMLNonSpecificTag' and share your opinion.")
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if start_mark is None:
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start_mark = end_mark = self.peek_token().start_mark
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event = None
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implicit = (tag is None or tag == '!')
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if indentless_sequence and self.check_token(BlockEntryToken):
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end_mark = self.peek_token().end_mark
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event = SequenceStartEvent(anchor, tag, implicit,
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start_mark, end_mark)
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self.state = self.parse_indentless_sequence_entry
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else:
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if self.check_token(ScalarToken):
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token = self.get_token()
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end_mark = token.end_mark
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if (token.plain and tag is None) or tag == '!':
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implicit = (True, False)
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elif tag is None:
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implicit = (False, True)
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else:
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implicit = (False, False)
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event = ScalarEvent(anchor, tag, implicit, token.value,
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start_mark, end_mark, style=token.style)
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self.state = self.states.pop()
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elif self.check_token(FlowSequenceStartToken):
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end_mark = self.peek_token().end_mark
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event = SequenceStartEvent(anchor, tag, implicit,
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start_mark, end_mark, flow_style=True)
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self.state = self.parse_flow_sequence_first_entry
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elif self.check_token(FlowMappingStartToken):
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end_mark = self.peek_token().end_mark
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event = MappingStartEvent(anchor, tag, implicit,
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start_mark, end_mark, flow_style=True)
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self.state = self.parse_flow_mapping_first_key
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elif block and self.check_token(BlockSequenceStartToken):
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end_mark = self.peek_token().start_mark
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event = SequenceStartEvent(anchor, tag, implicit,
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start_mark, end_mark, flow_style=False)
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self.state = self.parse_block_sequence_first_entry
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elif block and self.check_token(BlockMappingStartToken):
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end_mark = self.peek_token().start_mark
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event = MappingStartEvent(anchor, tag, implicit,
|
||
|
|
start_mark, end_mark, flow_style=False)
|
||
|
|
self.state = self.parse_block_mapping_first_key
|
||
|
|
elif anchor is not None or tag is not None:
|
||
|
|
# Empty scalars are allowed even if a tag or an anchor is
|
||
|
|
# specified.
|
||
|
|
event = ScalarEvent(anchor, tag, (implicit, False), '',
|
||
|
|
start_mark, end_mark)
|
||
|
|
self.state = self.states.pop()
|
||
|
|
else:
|
||
|
|
if block:
|
||
|
|
node = 'block'
|
||
|
|
else:
|
||
|
|
node = 'flow'
|
||
|
|
token = self.peek_token()
|
||
|
|
raise ParserError("while parsing a %s node" % node, start_mark,
|
||
|
|
"expected the node content, but found %r" % token.id,
|
||
|
|
token.start_mark)
|
||
|
|
return event
|
||
|
|
|
||
|
|
# block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
|
||
|
|
|
||
|
|
def parse_block_sequence_first_entry(self):
|
||
|
|
token = self.get_token()
|
||
|
|
self.marks.append(token.start_mark)
|
||
|
|
return self.parse_block_sequence_entry()
|
||
|
|
|
||
|
|
def parse_block_sequence_entry(self):
|
||
|
|
if self.check_token(BlockEntryToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(BlockEntryToken, BlockEndToken):
|
||
|
|
self.states.append(self.parse_block_sequence_entry)
|
||
|
|
return self.parse_block_node()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_block_sequence_entry
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
if not self.check_token(BlockEndToken):
|
||
|
|
token = self.peek_token()
|
||
|
|
raise ParserError("while parsing a block collection", self.marks[-1],
|
||
|
|
"expected <block end>, but found %r" % token.id, token.start_mark)
|
||
|
|
token = self.get_token()
|
||
|
|
event = SequenceEndEvent(token.start_mark, token.end_mark)
|
||
|
|
self.state = self.states.pop()
|
||
|
|
self.marks.pop()
|
||
|
|
return event
|
||
|
|
|
||
|
|
# indentless_sequence ::= (BLOCK-ENTRY block_node?)+
|
||
|
|
|
||
|
|
def parse_indentless_sequence_entry(self):
|
||
|
|
if self.check_token(BlockEntryToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(BlockEntryToken,
|
||
|
|
KeyToken, ValueToken, BlockEndToken):
|
||
|
|
self.states.append(self.parse_indentless_sequence_entry)
|
||
|
|
return self.parse_block_node()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_indentless_sequence_entry
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
token = self.peek_token()
|
||
|
|
event = SequenceEndEvent(token.start_mark, token.start_mark)
|
||
|
|
self.state = self.states.pop()
|
||
|
|
return event
|
||
|
|
|
||
|
|
# block_mapping ::= BLOCK-MAPPING_START
|
||
|
|
# ((KEY block_node_or_indentless_sequence?)?
|
||
|
|
# (VALUE block_node_or_indentless_sequence?)?)*
|
||
|
|
# BLOCK-END
|
||
|
|
|
||
|
|
def parse_block_mapping_first_key(self):
|
||
|
|
token = self.get_token()
|
||
|
|
self.marks.append(token.start_mark)
|
||
|
|
return self.parse_block_mapping_key()
|
||
|
|
|
||
|
|
def parse_block_mapping_key(self):
|
||
|
|
if self.check_token(KeyToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(KeyToken, ValueToken, BlockEndToken):
|
||
|
|
self.states.append(self.parse_block_mapping_value)
|
||
|
|
return self.parse_block_node_or_indentless_sequence()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_block_mapping_value
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
if not self.check_token(BlockEndToken):
|
||
|
|
token = self.peek_token()
|
||
|
|
raise ParserError("while parsing a block mapping", self.marks[-1],
|
||
|
|
"expected <block end>, but found %r" % token.id, token.start_mark)
|
||
|
|
token = self.get_token()
|
||
|
|
event = MappingEndEvent(token.start_mark, token.end_mark)
|
||
|
|
self.state = self.states.pop()
|
||
|
|
self.marks.pop()
|
||
|
|
return event
|
||
|
|
|
||
|
|
def parse_block_mapping_value(self):
|
||
|
|
if self.check_token(ValueToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(KeyToken, ValueToken, BlockEndToken):
|
||
|
|
self.states.append(self.parse_block_mapping_key)
|
||
|
|
return self.parse_block_node_or_indentless_sequence()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_block_mapping_key
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
else:
|
||
|
|
self.state = self.parse_block_mapping_key
|
||
|
|
token = self.peek_token()
|
||
|
|
return self.process_empty_scalar(token.start_mark)
|
||
|
|
|
||
|
|
# flow_sequence ::= FLOW-SEQUENCE-START
|
||
|
|
# (flow_sequence_entry FLOW-ENTRY)*
|
||
|
|
# flow_sequence_entry?
|
||
|
|
# FLOW-SEQUENCE-END
|
||
|
|
# flow_sequence_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
|
||
|
|
#
|
||
|
|
# Note that while production rules for both flow_sequence_entry and
|
||
|
|
# flow_mapping_entry are equal, their interpretations are different.
|
||
|
|
# For `flow_sequence_entry`, the part `KEY flow_node? (VALUE flow_node?)?`
|
||
|
|
# generate an inline mapping (set syntax).
|
||
|
|
|
||
|
|
def parse_flow_sequence_first_entry(self):
|
||
|
|
token = self.get_token()
|
||
|
|
self.marks.append(token.start_mark)
|
||
|
|
return self.parse_flow_sequence_entry(first=True)
|
||
|
|
|
||
|
|
def parse_flow_sequence_entry(self, first=False):
|
||
|
|
if not self.check_token(FlowSequenceEndToken):
|
||
|
|
if not first:
|
||
|
|
if self.check_token(FlowEntryToken):
|
||
|
|
self.get_token()
|
||
|
|
else:
|
||
|
|
token = self.peek_token()
|
||
|
|
raise ParserError("while parsing a flow sequence", self.marks[-1],
|
||
|
|
"expected ',' or ']', but got %r" % token.id, token.start_mark)
|
||
|
|
|
||
|
|
if self.check_token(KeyToken):
|
||
|
|
token = self.peek_token()
|
||
|
|
event = MappingStartEvent(None, None, True,
|
||
|
|
token.start_mark, token.end_mark,
|
||
|
|
flow_style=True)
|
||
|
|
self.state = self.parse_flow_sequence_entry_mapping_key
|
||
|
|
return event
|
||
|
|
elif not self.check_token(FlowSequenceEndToken):
|
||
|
|
self.states.append(self.parse_flow_sequence_entry)
|
||
|
|
return self.parse_flow_node()
|
||
|
|
token = self.get_token()
|
||
|
|
event = SequenceEndEvent(token.start_mark, token.end_mark)
|
||
|
|
self.state = self.states.pop()
|
||
|
|
self.marks.pop()
|
||
|
|
return event
|
||
|
|
|
||
|
|
def parse_flow_sequence_entry_mapping_key(self):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(ValueToken,
|
||
|
|
FlowEntryToken, FlowSequenceEndToken):
|
||
|
|
self.states.append(self.parse_flow_sequence_entry_mapping_value)
|
||
|
|
return self.parse_flow_node()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_flow_sequence_entry_mapping_value
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
|
||
|
|
def parse_flow_sequence_entry_mapping_value(self):
|
||
|
|
if self.check_token(ValueToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(FlowEntryToken, FlowSequenceEndToken):
|
||
|
|
self.states.append(self.parse_flow_sequence_entry_mapping_end)
|
||
|
|
return self.parse_flow_node()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_flow_sequence_entry_mapping_end
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
else:
|
||
|
|
self.state = self.parse_flow_sequence_entry_mapping_end
|
||
|
|
token = self.peek_token()
|
||
|
|
return self.process_empty_scalar(token.start_mark)
|
||
|
|
|
||
|
|
def parse_flow_sequence_entry_mapping_end(self):
|
||
|
|
self.state = self.parse_flow_sequence_entry
|
||
|
|
token = self.peek_token()
|
||
|
|
return MappingEndEvent(token.start_mark, token.start_mark)
|
||
|
|
|
||
|
|
# flow_mapping ::= FLOW-MAPPING-START
|
||
|
|
# (flow_mapping_entry FLOW-ENTRY)*
|
||
|
|
# flow_mapping_entry?
|
||
|
|
# FLOW-MAPPING-END
|
||
|
|
# flow_mapping_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
|
||
|
|
|
||
|
|
def parse_flow_mapping_first_key(self):
|
||
|
|
token = self.get_token()
|
||
|
|
self.marks.append(token.start_mark)
|
||
|
|
return self.parse_flow_mapping_key(first=True)
|
||
|
|
|
||
|
|
def parse_flow_mapping_key(self, first=False):
|
||
|
|
if not self.check_token(FlowMappingEndToken):
|
||
|
|
if not first:
|
||
|
|
if self.check_token(FlowEntryToken):
|
||
|
|
self.get_token()
|
||
|
|
else:
|
||
|
|
token = self.peek_token()
|
||
|
|
raise ParserError("while parsing a flow mapping", self.marks[-1],
|
||
|
|
"expected ',' or '}', but got %r" % token.id, token.start_mark)
|
||
|
|
if self.check_token(KeyToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(ValueToken,
|
||
|
|
FlowEntryToken, FlowMappingEndToken):
|
||
|
|
self.states.append(self.parse_flow_mapping_value)
|
||
|
|
return self.parse_flow_node()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_flow_mapping_value
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
elif not self.check_token(FlowMappingEndToken):
|
||
|
|
self.states.append(self.parse_flow_mapping_empty_value)
|
||
|
|
return self.parse_flow_node()
|
||
|
|
token = self.get_token()
|
||
|
|
event = MappingEndEvent(token.start_mark, token.end_mark)
|
||
|
|
self.state = self.states.pop()
|
||
|
|
self.marks.pop()
|
||
|
|
return event
|
||
|
|
|
||
|
|
def parse_flow_mapping_value(self):
|
||
|
|
if self.check_token(ValueToken):
|
||
|
|
token = self.get_token()
|
||
|
|
if not self.check_token(FlowEntryToken, FlowMappingEndToken):
|
||
|
|
self.states.append(self.parse_flow_mapping_key)
|
||
|
|
return self.parse_flow_node()
|
||
|
|
else:
|
||
|
|
self.state = self.parse_flow_mapping_key
|
||
|
|
return self.process_empty_scalar(token.end_mark)
|
||
|
|
else:
|
||
|
|
self.state = self.parse_flow_mapping_key
|
||
|
|
token = self.peek_token()
|
||
|
|
return self.process_empty_scalar(token.start_mark)
|
||
|
|
|
||
|
|
def parse_flow_mapping_empty_value(self):
|
||
|
|
self.state = self.parse_flow_mapping_key
|
||
|
|
return self.process_empty_scalar(self.peek_token().start_mark)
|
||
|
|
|
||
|
|
def process_empty_scalar(self, mark):
|
||
|
|
return ScalarEvent(None, None, (True, False), '', mark, mark)
|
||
|
|
|