def _create_xml_node(xast, node, context, insert_index=None):
if isinstance(xast, ast.Step):
if isinstance(xast.node_test, ast.NameTest):
# check the predicates (if any) to verify they're constructable
for pred in xast.predicates:
if not _predicate_is_constructible(pred):
msg = (
"Missing element for '%s', and node creation is "
+ "supported only for simple child and attribute "
+ "nodes with simple predicates."
) % (serialize(xast),)
raise Exception(msg)
# create the node itself
if xast.axis in (None, "child"):
new_node = _create_child_node(node, context, xast, insert_index)
elif xast.axis in ("@", "attribute"):
new_node = _create_attribute_node(node, context, xast)
# and create any nodes necessary for the predicates
for pred in xast.predicates:
_construct_predicate(pred, new_node, context)
return new_node
# if this is a text() node, we don't need to create anything further
# return the node that will be parent to text()
elif _is_text_nodetest(xast):
return node
elif isinstance(xast, ast.BinaryExpression):
if xast.op == "/":
left_xpath = serialize(xast.left)
left_node = _find_xml_node(left_xpath, node, context)
if left_node is None:
left_node = _create_xml_node(xast.left, node, context)
return _create_xml_node(xast.right, left_node, context)
# anything else, throw an exception:
msg = (
"Missing element for '%s', and node creation is supported " + "only for simple child and attribute nodes."
) % (serialize(xast),)
raise Exception(msg)
def set(self, xpath, xast, node, context, mapper, value):
xvalue = mapper.to_xml(value)
match = _find_xml_node(xpath, node, context)
if xvalue is None:
# match must be None. if it exists, delete it.
if match is not None:
removed = _remove_xml(xast, node, context)
# if a node can't be removed, warn since it could have unexpected results
if not removed:
logger.warn("""Could not remove xml for '%s' from %r""" % (serialize(xast), node))
else:
if match is None:
match = _create_xml_node(xast, node, context)
# terminal (rightmost) step informs how we update the xml
step = _find_terminal_step(xast)
_set_in_xml(match, xvalue, context, step)
def _remove_xml(xast, node, context):
"Remove a node or attribute; returns True when something is deleted"
if isinstance(xast, ast.Step):
if isinstance(xast.node_test, ast.NameTest):
if xast.axis in (None, "child"):
return _remove_child_node(node, context, xast)
elif xast.axis in ("@", "attribute"):
return _remove_attribute_node(node, context, xast)
# special case for text()
# since it can't be removed, at least clear out any value in the text node
elif _is_text_nodetest(xast):
node.text = ""
return True
elif isinstance(xast, ast.BinaryExpression):
if xast.op == "/":
left_xpath = serialize(xast.left)
left_node = _find_xml_node(left_xpath, node, context)
if left_node is not None:
return _remove_xml(xast.right, left_node, context)
return False
def round_trip(self, xpath_str):
xp = xpath.parse(xpath_str)
self.assertEqual(xpath_str, serialize(xp))
def _remove_child_node(node, context, xast):
xpath = serialize(xast)
child = _find_xml_node(xpath, node, context)
if child is not None:
node.remove(child)
return True
