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# -*- coding: utf-8 -*-
#
# python-json-patch - An implementation of the JSON Patch format
# https://github.com/stefankoegl/python-json-patch
#
# Copyright (c) 2011 Stefan Kögl <stefan@skoegl.net>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# 3. The name of the author may not be used to endorse or promote products
# derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
"""Apply JSON-Patches according to http://tools.ietf.org/html/draft-pbryan-json-patch-01"""
# Will be parsed by setup.py to determine package metadata
__author__ = 'Stefan Kögl <stefan@skoegl.net>'
__version__ = '0.1'
__website__ = 'https://github.com/stefankoegl/python-json-patch'
__license__ = 'Modified BSD License'
import copy
import json
class JsonPatchException(Exception):
pass
class JsonPatch(object):
""" A JSON Patch is a list of Patch Operations """
def __init__(self, patch):
self.patch = patch
self.OPERATIONS = {
'remove': RemoveOperation,
'add': AddOperation,
'replace': ReplaceOperation,
}
@classmethod
def from_string(cls, patch_str):
patch = json.loads(patch_str)
return cls(patch)
def apply(self, obj):
""" Applies the patch to a copy of the given object """
obj = copy.deepcopy(obj)
for operation in self.patch:
op = self._get_operation(operation)
op.apply(obj)
return obj
def _get_operation(self, operation):
for action, op_cls in self.OPERATIONS.items():
if action in operation:
location = operation[action]
op = op_cls(location, operation)
return op
raise JsonPatchException("invalid operation '%s'" % operation)
class PatchOperation(object):
""" A single operation inside a JSON Patch """
def __init__(self, location, operation):
self.location = location
self.operation = operation
def locate(self, obj, location, last_must_exist=True):
""" Walks through the object according to location
Returns the last step as (sub-object, last location-step) """
parts = location.split('/')
if parts.pop(0) != '':
raise JsonPatchException('location must starts with /')
for part in parts[:-1]:
obj, loc_part = self._step(obj, part)
_, last_loc = self._step(obj, parts[-1], must_exist=last_must_exist)
return obj, last_loc
def _step(self, obj, loc_part, must_exist=True):
""" Goes one step in a locate() call """
# Its not clear if a location "1" should be considered as 1 or "1"
# We prefer the integer-variant if possible
part_variants = self._try_parse(loc_part) + [loc_part]
for variant in part_variants:
try:
return obj[variant], variant
except:
continue
if must_exist:
raise JsonPatchException('key %s not found' % loc_part)
else:
return obj, part_variants[0]
@staticmethod
def _try_parse(val, cls=int):
try:
return [cls(val)]
except:
return []
class RemoveOperation(PatchOperation):
""" Removes an object property or an array element
>>> obj = { 'baz': 'qux', 'foo': 'bar' }
>>> patch = JsonPatch( [ { 'remove': '/baz' } ] )
>>> patch.apply(obj)
{'foo': 'bar'}
>>> obj = { 'foo': [ 'bar', 'qux', 'baz' ] }
>>> patch = JsonPatch( [ { "remove": "/foo/1" } ] )
>>> patch.apply(obj)
{'foo': ['bar', 'baz']}
"""
def apply(self, obj):
subobj, part = self.locate(obj, self.location)
del subobj[part]
class AddOperation(PatchOperation):
""" Adds an object property or an array element
>>> obj = { "foo": "bar" }
>>> patch = JsonPatch([ { "add": "/baz", "value": "qux" } ])
>>> patch.apply(obj)
{'foo': 'bar', 'baz': 'qux'}
>>> obj = { "foo": [ "bar", "baz" ] }
>>> patch = JsonPatch([ { "add": "/foo/1", "value": "qux" } ])
>>> patch.apply(obj)
{'foo': ['bar', 'qux', 'baz']}
"""
def apply(self, obj):
value = self.operation["value"]
subobj, part = self.locate(obj, self.location, last_must_exist=False)
if isinstance(subobj, list):
if part > len(subobj) or part < 0:
raise JsonPatchException("can't insert outside of list")
subobj.insert(part, value)
elif isinstance(subobj, dict):
if part in subobj:
raise JsonPatchException("object '%s' already exists" % part)
subobj[part] = value
else:
raise JsonPatchException("can't add to type '%s'" % subobj.__class__.__name__)
class ReplaceOperation(PatchOperation):
""" Replaces a value
>>> obj = { "baz": "qux", "foo": "bar" }
>>> patch = JsonPatch([ { "replace": "/baz", "value": "boo" } ])
>>> patch.apply(obj)
{'foo': 'bar', 'baz': 'boo'}
"""
def apply(self, obj):
location = self. operation["replace"]
value = self.operation["value"]
subobj, part = self.locate(obj, self.location)
if isinstance(subobj, list):
if part > len(subobj) or part < 0:
raise JsonPatchException("can't replace outside of list")
elif isinstance(subobj, dict):
if not part in subobj:
raise JsonPatchException("can't replace non-existant object '%s'" % part)
else:
raise JsonPatchException("can't replace in type '%s'" % subobj.__class__.__name__)
subobj[part] = value
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