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__all__ = ['Composer', 'ComposerError']
from .error import MarkedYAMLError
from .events import *
from .nodes import *
class ComposerError(MarkedYAMLError):
pass
class Composer:
def __init__(self):
self.anchors = {}
def check_node(self):
# Drop the STREAM-START event.
if self.check_event(StreamStartEvent):
self.get_event()
# If there are more documents available?
return not self.check_event(StreamEndEvent)
def get_node(self):
# Get the root node of the next document.
if not self.check_event(StreamEndEvent):
return self.compose_document()
def get_single_node(self):
# Drop the STREAM-START event.
self.get_event()
# Compose a document if the stream is not empty.
document = None
if not self.check_event(StreamEndEvent):
document = self.compose_document()
# Ensure that the stream contains no more documents.
if not self.check_event(StreamEndEvent):
event = self.get_event()
raise ComposerError("expected a single document in the stream",
document.start_mark, "but found another document",
event.start_mark)
# Drop the STREAM-END event.
self.get_event()
return document
def compose_document(self):
# Drop the DOCUMENT-START event.
self.get_event()
# Compose the root node.
node = self.compose_node(None, None)
# Drop the DOCUMENT-END event.
self.get_event()
self.anchors = {}
return node
def compose_node(self, parent, index):
if self.check_event(AliasEvent):
event = self.get_event()
anchor = event.anchor
if anchor not in self.anchors:
raise ComposerError(None, None, "found undefined alias %r"
% anchor, event.start_mark)
return self.anchors[anchor]
event = self.peek_event()
anchor = event.anchor
if anchor is not None:
if anchor in self.anchors:
raise ComposerError("found duplicate anchor %r; first occurence"
% anchor, self.anchors[anchor].start_mark,
"second occurence", event.start_mark)
self.descend_resolver(parent, index)
if self.check_event(ScalarEvent):
node = self.compose_scalar_node(anchor)
elif self.check_event(SequenceStartEvent):
node = self.compose_sequence_node(anchor)
elif self.check_event(MappingStartEvent):
node = self.compose_mapping_node(anchor)
self.ascend_resolver()
return node
def compose_scalar_node(self, anchor):
event = self.get_event()
tag = event.tag
if tag is None or tag == '!':
tag = self.resolve(ScalarNode, event.value, event.implicit)
node = ScalarNode(tag, event.value,
event.start_mark, event.end_mark, style=event.style)
if anchor is not None:
self.anchors[anchor] = node
return node
def compose_sequence_node(self, anchor):
start_event = self.get_event()
tag = start_event.tag
if tag is None or tag == '!':
tag = self.resolve(SequenceNode, None, start_event.implicit)
node = SequenceNode(tag, [],
start_event.start_mark, None,
flow_style=start_event.flow_style)
if anchor is not None:
self.anchors[anchor] = node
index = 0
while not self.check_event(SequenceEndEvent):
node.value.append(self.compose_node(node, index))
index += 1
end_event = self.get_event()
node.end_mark = end_event.end_mark
return node
def compose_mapping_node(self, anchor):
start_event = self.get_event()
tag = start_event.tag
if tag is None or tag == '!':
tag = self.resolve(MappingNode, None, start_event.implicit)
node = MappingNode(tag, [],
start_event.start_mark, None,
flow_style=start_event.flow_style)
if anchor is not None:
self.anchors[anchor] = node
while not self.check_event(MappingEndEvent):
#key_event = self.peek_event()
item_key = self.compose_node(node, None)
#if item_key in node.value:
# raise ComposerError("while composing a mapping", start_event.start_mark,
# "found duplicate key", key_event.start_mark)
item_value = self.compose_node(node, item_key)
#node.value[item_key] = item_value
node.value.append((item_key, item_value))
end_event = self.get_event()
node.end_mark = end_event.end_mark
return node