from dataclasses import dataclass
from dataclasses import field
from dataclasses import is_dataclass
from enum import Enum
from io import StringIO
from typing import Any
from typing import Dict
from typing import Generator
from typing import List
from typing import Optional
from typing import TextIO
from typing import Type
from xml.etree.ElementTree import QName
from xsdata.exceptions import SerializerError
from xsdata.formats.bindings import AbstractSerializer
from xsdata.formats.converter import converter
from xsdata.formats.dataclass.context import XmlContext
from xsdata.formats.dataclass.models.elements import XmlMeta
from xsdata.formats.dataclass.models.elements import XmlVar
from xsdata.formats.dataclass.models.generics import AnyElement
from xsdata.formats.dataclass.models.generics import DerivedElement
from xsdata.formats.dataclass.serializers.config import SerializerConfig
from xsdata.formats.dataclass.serializers.mixins import XmlWriter
from xsdata.formats.dataclass.serializers.mixins import XmlWriterEvent
from xsdata.formats.dataclass.serializers.writers import default_writer
from xsdata.models.enums import DataType
from xsdata.models.enums import QNames
from xsdata.utils import namespaces
from xsdata.utils.constants import EMPTY_MAP
from xsdata.utils.namespaces import split_qname
NoneStr = Optional[str]
[docs]@dataclass
class XmlSerializer(AbstractSerializer):
"""
Xml serializer for dataclasses.
:param config: Serializer configuration
:param context: Model context provider
:param writer: Override default XmlWriter
"""
config: SerializerConfig = field(default_factory=SerializerConfig)
context: XmlContext = field(default_factory=XmlContext)
writer: Type[XmlWriter] = field(default=default_writer())
[docs] def render(self, obj: Any, ns_map: Optional[Dict] = None) -> str:
"""
Convert and return the given object tree as xml string.
:param obj: The input dataclass instance
:param ns_map: User defined namespace prefix-URI map
"""
output = StringIO()
self.write(output, obj, ns_map)
return output.getvalue()
[docs] def write(self, out: TextIO, obj: Any, ns_map: Optional[Dict] = None):
"""
Write the given object tree to the output text stream.
:param out: The output stream
:param obj: The input dataclass instance
:param ns_map: User defined namespace prefix-URI map
"""
events = self.write_object(obj)
handler = self.writer(
config=self.config,
output=out,
ns_map=namespaces.clean_prefixes(ns_map) if ns_map else {},
)
handler.write(events)
[docs] def write_object(self, obj: Any):
"""Produce an events stream from a dataclass or a derived element."""
qname = xsi_type = None
if isinstance(obj, DerivedElement):
meta = self.context.build(obj.value.__class__)
xsi_type = QName(meta.source_qname)
qname = obj.qname
obj = obj.value
yield from self.write_dataclass(obj, qname=qname, xsi_type=xsi_type)
[docs] def write_dataclass(
self,
obj: Any,
namespace: NoneStr = None,
qname: NoneStr = None,
nillable: bool = False,
xsi_type: Optional[QName] = None,
) -> Generator:
"""
Produce an events stream from a dataclass.
Optionally override the qualified name and the xsi properties
type and nil.
"""
meta = self.context.build(obj.__class__, namespace)
qname = qname or meta.qname
nillable = nillable or meta.nillable
namespace, tag = split_qname(qname)
yield XmlWriterEvent.START, qname
for key, value in self.next_attribute(obj, meta, nillable, xsi_type):
yield XmlWriterEvent.ATTR, key, value
for var, value in self.next_value(obj, meta):
if value is not None or var.nillable:
yield from self.write_value(value, var, namespace)
yield XmlWriterEvent.END, qname
[docs] def write_xsi_type(self, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""Produce an events stream from a dataclass for the given var with
with xsi abstract type check for non wildcards."""
if var.is_wildcard:
yield from self.write_dataclass(value, namespace)
else:
xsi_type = self.xsi_type(var, value, namespace)
yield from self.write_dataclass(
value, namespace, var.qname, var.nillable, xsi_type
)
[docs] def write_value(self, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""
Delegates the given value to the correct writer according to the
variable metadata.
The order of the checks is important as more than one condition
can be true.
"""
if var.mixed:
yield from self.write_mixed_content(value, var, namespace)
elif var.is_text:
yield from self.write_data(value, var, namespace)
elif var.tokens:
yield from self.write_tokens(value, var, namespace)
elif var.is_elements:
yield from self.write_elements(value, var, namespace)
elif var.list_element and isinstance(value, list):
yield from self.write_list(value, var, namespace)
else:
yield from self.write_any_type(value, var, namespace)
[docs] def write_list(self, values: List, var: XmlVar, namespace: NoneStr) -> Generator:
"""Produce an events stream for the given list of values."""
for value in values:
yield from self.write_value(value, var, namespace)
[docs] def write_tokens(self, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""Produce an events stream for the given tokens list or list of tokens
lists."""
if value or var.nillable:
if value and isinstance(value[0], list):
for val in value:
yield from self.write_element(val, var, namespace)
else:
yield from self.write_element(value, var, namespace)
[docs] def write_mixed_content(
self, values: List, var: XmlVar, namespace: NoneStr
) -> Generator:
"""Produce an events stream for the given list of mixed type
objects."""
for value in values:
yield from self.write_any_type(value, var, namespace)
[docs] def write_any_type(self, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""
Produce an events stream for the given object.
The object can be a dataclass or a generic object or any other
simple type.
"""
if isinstance(value, AnyElement):
yield from self.write_wildcard(value, var, namespace)
elif isinstance(value, DerivedElement):
yield from self.write_derived_element(value, var, namespace)
elif is_dataclass(value):
yield from self.write_xsi_type(value, var, namespace)
elif var.is_element:
yield from self.write_element(value, var, namespace)
else:
yield from self.write_data(value, var, namespace)
def write_derived_element(
self, value: DerivedElement, var: XmlVar, namespace: NoneStr
) -> Generator:
if is_dataclass(value.value):
xsi_type = None
if value.type:
meta = self.context.build(value.value.__class__)
xsi_type = QName(meta.source_qname)
yield from self.write_dataclass(
value.value, namespace, qname=value.qname, xsi_type=xsi_type
)
else:
datatype = DataType.from_value(value.value)
yield XmlWriterEvent.START, value.qname
yield XmlWriterEvent.ATTR, QNames.XSI_TYPE, QName(str(datatype))
yield XmlWriterEvent.DATA, value.value
yield XmlWriterEvent.END, value.qname
[docs] def write_wildcard(
self, value: AnyElement, var: XmlVar, namespace: NoneStr
) -> Generator:
"""Produce an element events stream for the given generic object."""
if value.qname:
namespace, tag = split_qname(value.qname)
yield XmlWriterEvent.START, value.qname
for key, val in value.attributes.items():
yield XmlWriterEvent.ATTR, key, val
yield XmlWriterEvent.DATA, value.text
for child in value.children:
yield from self.write_any_type(child, var, namespace)
if value.qname:
yield XmlWriterEvent.END, value.qname
if value.tail:
yield XmlWriterEvent.DATA, value.tail
[docs] def xsi_type(self, var: XmlVar, value: Any, namespace: NoneStr) -> Optional[QName]:
"""Get xsi:type if the given value is a derived instance."""
if not value or value.__class__ in var.types:
return None
clazz = var.clazz
if clazz is None or self.context.is_derived(value, clazz):
meta = self.context.fetch(value.__class__, namespace)
return QName(meta.source_qname)
raise SerializerError(
f"{value.__class__.__name__} is not derived from {clazz.__name__}"
)
[docs] def write_elements(self, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""Produce an events stream from compound elements field."""
if isinstance(value, list):
for choice in value:
yield from self.write_choice(choice, var, namespace)
else:
yield from self.write_choice(value, var, namespace)
[docs] def write_choice(self, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""
Produce an events stream for the given value of a compound elements
field.
The value can be anything as long as we can match the qualified
name or its type to a choice.
"""
if isinstance(value, DerivedElement):
choice = var.find_choice(value.qname)
value = value.value
func = self.write_xsi_type if is_dataclass(value) else self.write_element
elif isinstance(value, AnyElement) and value.qname:
choice = var.find_choice(value.qname)
func = self.write_any_type
else:
choice = var.find_value_choice(value)
func = self.write_value
if not choice:
raise SerializerError(
f"XmlElements undefined choice: `{var.name}` for `{type(value)}`"
)
yield from func(value, choice, namespace)
[docs] @classmethod
def write_element(cls, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""Produce an element events stream for the given simple type value."""
yield XmlWriterEvent.START, var.qname
if var.nillable:
yield XmlWriterEvent.ATTR, QNames.XSI_NIL, "true"
if value is not None and value != "" and var.any_type:
datatype = DataType.from_value(value)
if datatype != DataType.STRING:
yield XmlWriterEvent.ATTR, QNames.XSI_TYPE, QName(str(datatype))
yield XmlWriterEvent.DATA, cls.encode(value, var)
yield XmlWriterEvent.END, var.qname
[docs] @classmethod
def write_data(cls, value: Any, var: XmlVar, namespace: NoneStr) -> Generator:
"""Produce a data event for the given value."""
yield XmlWriterEvent.DATA, cls.encode(value, var)
[docs] @classmethod
def next_value(cls, obj: Any, meta: XmlMeta):
"""
Return the non attribute variables with their object values in the
correct order according to their definition and the sequential metadata
property.
Sequential fields need to be rendered together in parallel order
eg: <a1/><a2/><a1/><a/2></a1>
"""
index = 0
attrs = meta.get_element_vars()
stop = len(attrs)
while index < stop:
var = attrs[index]
if not var.sequential:
yield var, getattr(obj, var.name)
index += 1
continue
indices = range(index + 1, stop)
end = next((i for i in indices if not attrs[i].sequential), stop)
sequence = attrs[index:end]
index = end
j = 0
rolling = True
while rolling:
rolling = False
for var in sequence:
values = getattr(obj, var.name)
if j < len(values):
rolling = True
yield var, values[j]
j += 1
[docs] @classmethod
def next_attribute(
cls, obj: Any, meta: XmlMeta, xsi_nil: bool, xsi_type: Optional[QName]
) -> Generator:
"""
Return the attribute variables with their object values.
Ignores None values and empty lists. Optionally include the xsi
properties type and nil.
"""
for var in meta.get_attribute_vars():
if var.is_attribute:
value = getattr(obj, var.name)
if value is None or isinstance(value, list) and not value:
continue
yield var.qname, cls.encode(value, var)
else:
yield from getattr(obj, var.name, EMPTY_MAP).items()
if xsi_type:
yield QNames.XSI_TYPE, xsi_type
if xsi_nil:
yield QNames.XSI_NIL, "true"
[docs] @classmethod
def encode(cls, value: Any, var: XmlVar) -> Any:
"""
Encode values for xml serialization.
Converts values to strings. QName instances is an exception,
those values need to wait until the XmlWriter assigns prefixes
to namespaces per element node. Enums and Tokens may contain
QName(s) so they also get a special treatment.
We can't do all the conversions in the writer because we would
need to carry the xml vars inside the writer. Instead of that
we do the easy encoding here and leave the qualified names for
later.
"""
if isinstance(value, (str, QName)) or var is None:
return value
if isinstance(value, tuple) and hasattr(value, "_fields"):
return converter.serialize(value, format=var.format)
if isinstance(value, (tuple, list)):
return [cls.encode(v, var) for v in value]
if isinstance(value, Enum):
return cls.encode(value.value, var)
return converter.serialize(value, format=var.format)