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# Copyright (C) 2020 The Android Open Source Project
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.
"""A library containing functions for diffing XML elements."""
import textwrap
from typing import Any, Callable, Dict, Set
import xml.etree.ElementTree as ET
import dataclasses
Element = ET.Element
_INDENT = (' ' * 2)
class Change:
value_from: str
value_to: str
def __repr__(self):
return f'{self.value_from} -> {self.value_to}'
class ChangeMap:
"""A collection of changes broken down by added, removed and modified.
added: A dictionary of string identifiers to the added string.
removed: A dictionary of string identifiers to the removed string.
modified: A dictionary of string identifiers to the changed object.
added: Dict[str, str] = dataclasses.field(default_factory=dict)
removed: Dict[str, str] = dataclasses.field(default_factory=dict)
modified: Dict[str, Any] = dataclasses.field(default_factory=dict)
def __repr__(self):
ret_str = ''
if self.added:
ret_str += 'Added:\n'
for value in self.added.values():
ret_str += textwrap.indent(str(value) + '\n', _INDENT)
if self.removed:
ret_str += 'Removed:\n'
for value in self.removed.values():
ret_str += textwrap.indent(str(value) + '\n', _INDENT)
if self.modified:
ret_str += 'Modified:\n'
for name, value in self.modified.items():
ret_str += textwrap.indent(name + ':\n', _INDENT)
ret_str += textwrap.indent(str(value) + '\n', _INDENT * 2)
return ret_str
def __bool__(self):
return bool(self.added) or bool(self.removed) or bool(self.modified)
def element_string(e: Element) -> str:
return ET.tostring(e).decode(encoding='UTF-8').strip()
def attribute_changes(e1: Element, e2: Element,
ignored_attrs: Set[str]) -> ChangeMap:
"""Get the changes in attributes between two XML elements.
e1: the first xml element.
e2: the second xml element.
ignored_attrs: a set of attribute names to ignore changes.
A ChangeMap of attribute changes. Keyed by attribute name.
changes = ChangeMap()
attributes = set(e1.keys()) | set(e2.keys())
for attr in attributes:
if attr in ignored_attrs:
a1 = e1.get(attr)
a2 = e2.get(attr)
if a1 == a2:
elif not a1:
changes.added[attr] = a2 or ''
elif not a2:
changes.removed[attr] = a1
changes.modified[attr] = Change(value_from=a1, value_to=a2)
return changes
def compare_subelements(
tag: str,
p1: Element,
p2: Element,
ignored_attrs: Set[str],
key_fn: Callable[[Element], str],
diff_fn: Callable[[Element, Element, Set[str]], Any]) -> ChangeMap:
"""Get the changes between subelements of two parent elements.
tag: tag name for children element.
p1: the base parent xml element.
p2: the parent xml element to compare
ignored_attrs: a set of attribute names to ignore changes.
key_fn: Function that takes a subelement and returns a key
diff_fn: Function that take two subelements and a set of ignored
attributes, returns the differences
A ChangeMap object of the changes.
changes = ChangeMap()
group1 = {}
for e1 in p1.findall(tag):
group1[key_fn(e1)] = e1
for e2 in p2.findall(tag):
key = key_fn(e2)
e1 = group1.pop(key, None)
if e1 is None:
changes.added[key] = element_string(e2)
echange = diff_fn(e1, e2, ignored_attrs)
if echange:
changes.modified[key] = echange
for name, e1 in group1.items():
changes.removed[name] = element_string(e1)
return changes