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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):
# 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 __iter__(self):
# Iterator protocol.
while not self.check_event(StreamEndEvent):
yield self.compose_document()
def compose_document(self):
# Drop the STREAM-START event.
if self.check_event(StreamStartEvent):
self.get_event()
# 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.complete_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.encode('utf-8'), 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.encode('utf-8'), 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 == u'!':
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 == u'!':
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 == u'!':
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
end_event = self.get_event()
node.end_mark = end_event.end_mark
return node
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