def __init__(self, notification_handler=None):
"""Initializes the loader with NotificationHandler."""
self._event = None
self._event_generator = iter([])
self._document = None
self._iterate_events = True
self._fatal_error_node = None
self.anchors = {}
self.notification_handler = notification_handler
if self.notification_handler is None:
self.notification_handler = NotificationHandler()
class Loader:
"""Generates DataNode structure from YAML document."""
def __init__(self, notification_handler=None):
"""Initializes the loader with NotificationHandler."""
self._event = None
self._event_generator = iter([])
self._document = None
self._iterate_events = True
self._fatal_error_node = None
self.anchors = {}
self.notification_handler = notification_handler
if self.notification_handler is None:
self.notification_handler = NotificationHandler()
def load(self, document):
"""Loads the YAML document and returns the root DataNode."""
if document is None:
return None
self._fatal_error_node = None
self._iterate_events = True
self.anchors = {}
self._document = document
self._event_generator = pyyaml.parse(self._document)
self._next_parse_event() # StreamStartEvent
self._next_parse_event() # DocumentStartEvent
self._next_parse_event() # first actual event
root = self._create_node()
if self._fatal_error_node:
if root.implementation != DataNode.Implementation.scalar:
# pylint: disable=no-member
root.set_child(self._fatal_error_node)
root.span.end = self._fatal_error_node.end
return root
def _next_parse_event(self):
"""
Attempts to get next parsing event and handles errors. When there
are no more valid parsing events, event is set to None.
"""
if self._iterate_events:
try:
# get next parsing event
self._event = next(self._event_generator)
except pyyaml.MarkedYAMLError as error:
# handle parsing error
self._event = None
self._iterate_events = False
start_pos = Position.from_yaml_error(error)
self._create_fatal_error_node(start_pos)
notification = Notification.from_name('SyntaxFatalError')
notification.span = self._fatal_error_node.span
self.notification_handler.report(notification)
except StopIteration:
# handle end of parsing events
self._event = None
self._iterate_events = False
def _create_node(self, parent=None):
"""Create a DataNode from parsing events."""
anchor = self._extract_anchor()
tag = self._extract_tag()
node = None
# TODO: Adapter pattern?
if tag is not None:
node = self._create_node_by_tag(tag)
elif isinstance(self._event, pyyaml.MappingStartEvent):
node = self._create_record_node()
elif isinstance(self._event, pyyaml.SequenceStartEvent):
node = self._create_array_node()
elif isinstance(self._event, pyyaml.ScalarEvent):
node = self._create_scalar_node()
elif isinstance(self._event, pyyaml.AliasEvent):
node = self._create_alias_node(anchor)
if node is not None:
node.parent = parent
# register anchor if it exists and node is not an alias
if anchor is not None and node.ref is None:
self._register_anchor(anchor, node)
return node
def _extract_anchor(self):
"""Extracts `TextValue` of anchor from the current event."""
value = getattr(self._event, 'anchor', None)
if value is None or value in ['*', '&']:
return None
anchor = TextValue(value)
symbol = '&'
if isinstance(self._event, pyyaml.AliasEvent):
symbol = '*'
anchor.span = self._extract_property_span(self._event.start_mark, symbol)
return anchor
def _extract_tag(self):
"""Extracts `TextValue` of tag from the current event."""
value = getattr(self._event, 'tag', None)
if value is None or value == '!':
return None
tag = TextValue(value)
tag.span = self._extract_property_span(self._event.start_mark, '!')
return tag
def _extract_property_span(self, start_mark, symbol):
"""
Create a `Span` from the first `symbol` at `start_mark`.
Used to get the span of node properties like anchors or tags.
"""
# set document to start at start_mark
lines = self._document.splitlines()
line_index = start_mark.line
line = lines[line_index]
line = line[start_mark.column:] # first line offset
expr = '[{symbol}]([a-zA-Z0-9_:-]+)'.format(symbol=symbol)
regex = re.compile(expr)
match = regex.search(line)
if match is not None: # set correct offset of match
start_column = start_mark.column + match.start(1)
end_column = start_mark.column + match.end(1)
while match is None and line_index < len(lines) - 1:
line_index += 1
line = lines[line_index]
match = regex.search(line)
start_column = locals().get('start_column', match.start(1))
end_column = locals().get('end_column', match.end(1))
start = Position(line_index + 1, start_column + 1)
end = Position(line_index + 1, end_column + 1)
return Span(start, end)
def _create_node_by_tag(self, tag):
"""
Creates either an abstract record (for app specific tags: !) or
scalar value of specified type (yaml tags - !!, tag:yaml.org,2002:)
"""
if tag.value.startswith('tag:yaml.org,2002:'):
node = self._create_scalar_node()
else: # abstract record
node = self._create_abstract_record(tag)
return node
def _create_scalar_node(self):
"""Creates a ScalarDataNode."""
node = ScalarDataNode()
tag = self._event.tag
if tag is None or not tag.startswith('tag:yaml.org,2002:'):
tag = resolve_scalar_tag(self._event.value)
node.span = Span.from_event(self._event)
try:
node.value = construct_scalar(self._event.value, tag)
except Exception as error:
notification = Notification.from_name('ConstructScalarError', error.args[0])
notification.span = node.span
self.notification_handler.report(notification)
return node
if node.value is None:
# alter position of empty node (so it can be selected)
node.span.end.column += 1
return node
def _create_abstract_record(self, tag):
"""Creates abstract record from parsing events."""
tag.value = tag.value[1:] # remove leading !
if isinstance(self._event, pyyaml.MappingStartEvent):
# classic abstract record node
node = self._create_record_node()
elif isinstance(self._event, pyyaml.ScalarEvent):
# scalar abstract node - either empty, or for autoconversion
temp_node = self._create_scalar_node()
if temp_node.value is None:
# empty node - construct as mapping
node = MappingDataNode()
node.span = temp_node.span
else: # may be used for autoconversion
node = temp_node
elif isinstance(self._event, pyyaml.SequenceStartEvent):
node = self._create_array_node()
node.type = tag
return node
def _create_record_node(self):
"""Creates a record node."""
node = MappingDataNode()
start_mark = self._event.start_mark
end_mark = self._event.end_mark
self._next_parse_event()
# create children
while (self._event is not None and
not isinstance(self._event, pyyaml.MappingEndEvent)):
key = self._create_record_key()
self._next_parse_event() # value event
if not key: # if key is invalid
continue
if self._event is None:
break # something went wrong, abandon ship!
if key.value == '<<': # handle merge
self._perform_merge(key, node)
self._next_parse_event()
continue
child_node = self._create_node(node)
self._next_parse_event()
if child_node is None: # i.e. unresolved alias
continue
child_node.key = key
node.set_child(child_node)
if self._event is not None: # update end_mark when map ends correctly
end_mark = self._event.end_mark
elif node.children:
end_mark = node.children[-1].span.end
end_mark.line -= 1
end_mark.column -= 1
node.span = Span.from_marks(start_mark, end_mark)
return node
def _create_record_key(self):
"""Creates `TextValue` of record key."""
# check if key is scalar
if not isinstance(self._event, pyyaml.ScalarEvent):
start_pos = Position.from_mark(self._event.start_mark)
self._create_fatal_error_node(start_pos)
notification = Notification.from_name('ComplexRecordKey')
notification.span = self._fatal_error_node.span
self.notification_handler.report(notification)
self._event = None
self._iterate_events = False
return None
key = TextValue()
key.value = self._event.value
key.span = Span.from_event(self._event)
return key
def _perform_merge(self, key, node):
"""Performs merge operation on record node."""
if isinstance(self._event, pyyaml.SequenceStartEvent):
self._next_parse_event()
while (self._event is not None and
not isinstance(self._event, pyyaml.SequenceEndEvent)):
self._merge_into_node(node)
self._next_parse_event()
else:
self._merge_into_node(node)
def _merge_into_node(self, node):
"""Merges a single alias node into this record node."""
# allow only alias nodes to be merged
if not isinstance(self._event, pyyaml.AliasEvent):
temp = self._create_node(node) # skip the node to avoid parsing error
notification = Notification.from_name('NoReferenceToMerge')
notification.span = temp.span
self.notification_handler.report(notification)
return
anchor = self._extract_anchor()
if anchor.value not in self.anchors:
notification = Notification.from_name('UndefinedAnchor', anchor.value)
notification.span = anchor.span
self.notification_handler.report(notification)
return
anchor_node = self.anchors[anchor.value]
if anchor_node.implementation != DataNode.Implementation.mapping:
notification = Notification.from_name('InvalidReferenceForMerge', anchor.value)
notification.span = anchor.span
self.notification_handler.report(notification)
return
for child in anchor_node.children:
if child.key.value not in node.children_keys:
node.set_child(copy.deepcopy(child))
return
def _create_array_node(self):
"""Creates an array node."""
node = SequenceDataNode()
start_mark = self._event.start_mark
end_mark = self._event.end_mark
self._next_parse_event()
while (self._event is not None and
not isinstance(self._event, pyyaml.SequenceEndEvent)):
key = TextValue(str(len(node.children)))
child_node = self._create_node(node)
self._next_parse_event()
if child_node is None: # i.e. unresolved alias
continue
child_node.key = key
node.children.append(child_node)
if self._event is not None: # update end_mark when array ends correctly
end_mark = self._event.end_mark
elif node.children:
end_mark = node.children[-1].span.end
end_mark.line -= 1
end_mark.column -= 1
node.span = Span.from_marks(start_mark, end_mark)
return node
def _create_alias_node(self, anchor):
"""Creates an alias node."""
if anchor.value not in self.anchors:
notification = Notification.from_name('UndefinedAnchor', anchor.value)
notification.span = anchor.span
self.notification_handler.report(notification)
return None
ref = self.anchors[anchor.value]
node = copy.deepcopy(ref)
node.anchor = anchor
node.ref = ref
# set correct node.span
node.span = copy.deepcopy(node.anchor.span)
start = node.span.start
node.span.start = Position(start.line, start.column - 1)
return node
def _register_anchor(self, anchor, node):
"""Registers an anchor to a node."""
node.anchor = anchor
if anchor.value in self.anchors:
notification = Notification.from_name('OverridingAnchor', anchor.value)
notification.span = anchor.span
self.notification_handler.report(notification)
self.anchors[anchor.value] = node
def _create_fatal_error_node(self, start_pos):
"""
Creates a non-existing node in the data tree
to wrap the content of the error (span) in a node.
"""
node = ScalarDataNode()
end_pos = Position.from_document_end(self._document)
node.span = Span(start_pos, end_pos)
node.key = TextValue('fatal_error')
node.origin = DataNode.Origin.error
node.hidden = True
self._fatal_error_node = node