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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 draft 08) """
# http://tools.ietf.org/html/draft-ietf-appsawg-json-patch-05
# Will be parsed by setup.py to determine package metadata
__author__ = 'Stefan Kögl <stefan@skoegl.net>'
__version__ = '0.11'
__website__ = 'https://github.com/stefankoegl/python-json-patch'
__license__ = 'Modified BSD License'
import copy
import sys
import json
import jsonpointer
if sys.version_info >= (3, 0):
basestring = (bytes, str)
JsonPointerException = jsonpointer.JsonPointerException
class JsonPatchException(Exception):
"""Base Json Patch exception"""
class JsonPatchConflict(JsonPatchException):
"""Raised if patch could not be applied due to conflict situation such as:
- attempt to add object key then it already exists;
- attempt to operate with nonexistence object key;
- attempt to insert value to array at position beyond of it size;
- etc.
"""
class JsonPatchTestFailed(JsonPatchException, AssertionError):
""" A Test operation failed """
def apply_patch(doc, patch, in_place=False):
"""Apply list of patches to specified json document.
:param doc: Document object.
:type doc: dict
:param patch: JSON patch as list of dicts or raw JSON-encoded string.
:type patch: list or str
:param in_place: While :const:`True` patch will modify target document.
By default patch will be applied to document copy.
:type in_place: bool
:return: Patched document object.
:rtype: dict
>>> doc = {'foo': 'bar'}
>>> other = apply_patch(doc, [{'op': 'add', 'path': '/baz', 'value': 'qux'}])
>>> doc is not other
True
>>> other
{'foo': 'bar', 'baz': 'qux'}
>>> apply_patch(doc, [{'op': 'add', 'path': '/baz', 'value': 'qux'}], in_place=True)
{'foo': 'bar', 'baz': 'qux'}
>>> doc == other
True
"""
if isinstance(patch, basestring):
patch = JsonPatch.from_string(patch)
else:
patch = JsonPatch(patch)
return patch.apply(doc, in_place)
def make_patch(src, dst):
"""Generates patch by comparing of two document objects. Actually is
a proxy to :meth:`JsonPatch.from_diff` method.
:param src: Data source document object.
:type src: dict
:param dst: Data source document object.
:type dst: dict
>>> src = {'foo': 'bar', 'numbers': [1, 3, 4, 8]}
>>> dst = {'baz': 'qux', 'numbers': [1, 4, 7]}
>>> patch = make_patch(src, dst)
>>> new = patch.apply(src)
>>> new == dst
True
"""
return JsonPatch.from_diff(src, dst)
class JsonPatch(object):
"""A JSON Patch is a list of Patch Operations.
>>> patch = JsonPatch([
... {'op': 'add', 'path': '/foo', 'value': 'bar'},
... {'op': 'add', 'path': '/baz', 'value': [1, 2, 3]},
... {'op': 'remove', 'path': '/baz/1'},
... {'op': 'test', 'path': '/baz', 'value': [1, 3]},
... {'op': 'replace', 'path': '/baz/0', 'value': 42},
... {'op': 'remove', 'path': '/baz/1'},
... ])
>>> doc = {}
>>> result = patch.apply(doc)
>>> expected = {'foo': 'bar', 'baz': [42]}
>>> result == expected
True
JsonPatch object is iterable, so you could easily access to each patch
statement in loop:
>>> lpatch = list(patch)
>>> expected = {'op': 'add', 'path': '/foo', 'value': 'bar'}
>>> lpatch[0] == expected
True
>>> lpatch == patch.patch
True
Also JsonPatch could be converted directly to :class:`bool` if it contains
any operation statements:
>>> bool(patch)
True
>>> bool(JsonPatch([]))
False
This behavior is very handy with :func:`make_patch` to write more readable
code:
>>> old = {'foo': 'bar', 'numbers': [1, 3, 4, 8]}
>>> new = {'baz': 'qux', 'numbers': [1, 4, 7]}
>>> patch = make_patch(old, new)
>>> if patch:
... # document have changed, do something useful
... patch.apply(old) #doctest: +ELLIPSIS
{...}
"""
def __init__(self, patch):
self.patch = patch
self.operations = {
'remove': RemoveOperation,
'add': AddOperation,
'replace': ReplaceOperation,
'move': MoveOperation,
'test': TestOperation,
'copy': CopyOperation,
}
def __str__(self):
"""str(self) -> self.to_string()"""
return self.to_string()
def __bool__(self):
return bool(self.patch)
__nonzero__ = __bool__
def __iter__(self):
return iter(self.patch)
def __hash__(self):
return hash(tuple(self._get_operation(op) for op in self.patch))
def __eq__(self, other):
if not isinstance(other, JsonPatch):
return False
return self.patch == other.patch
@classmethod
def from_string(cls, patch_str):
"""Creates JsonPatch instance from string source.
:param patch_str: JSON patch as raw string.
:type patch_str: str
:return: :class:`JsonPatch` instance.
"""
patch = json.loads(patch_str)
return cls(patch)
@classmethod
def from_diff(cls, src, dst):
"""Creates JsonPatch instance based on comparing of two document
objects. Json patch would be created for `src` argument against `dst`
one.
:param src: Data source document object.
:type src: dict
:param dst: Data source document object.
:type dst: dict
:return: :class:`JsonPatch` instance.
>>> src = {'foo': 'bar', 'numbers': [1, 3, 4, 8]}
>>> dst = {'baz': 'qux', 'numbers': [1, 4, 7]}
>>> patch = JsonPatch.from_diff(src, dst)
>>> new = patch.apply(src)
>>> new == dst
True
"""
def compare_values(path, value, other):
if value == other:
return
if isinstance(value, dict) and isinstance(other, dict):
for operation in compare_dict(path, value, other):
yield operation
elif isinstance(value, list) and isinstance(other, list):
for operation in compare_list(path, value, other):
yield operation
else:
yield {'op': 'replace', 'path': '/'.join(path), 'value': other}
def compare_dict(path, src, dst):
for key in src:
if key not in dst:
yield {'op': 'remove', 'path': '/'.join(path + [key])}
continue
current = path + [key]
for operation in compare_values(current, src[key], dst[key]):
yield operation
for key in dst:
if key not in src:
yield {'op': 'add', 'path': '/'.join(path + [key]), 'value': dst[key]}
def compare_list(path, src, dst):
lsrc, ldst = len(src), len(dst)
for idx in range(min(lsrc, ldst)):
current = path + [str(idx)]
for operation in compare_values(current, src[idx], dst[idx]):
yield operation
if lsrc < ldst:
for idx in range(lsrc, ldst):
current = path + [str(idx)]
yield {'op': 'add', 'path': '/'.join(current), 'value': dst[idx]}
elif lsrc > ldst:
for idx in reversed(range(ldst, lsrc)):
yield {'op': 'remove', 'path': '/'.join(path + [str(idx)])}
return cls(list(compare_dict([''], src, dst)))
def to_string(self):
"""Returns patch set as JSON string."""
return json.dumps(self.patch)
def apply(self, obj, in_place=False):
"""Applies the patch to given object.
:param obj: Document object.
:type obj: dict
:param in_place: Tweaks way how patch would be applied - directly to
specified `obj` or to his copy.
:type in_place: bool
:return: Modified `obj`.
"""
if not in_place:
obj = copy.deepcopy(obj)
for operation in self.patch:
operation = self._get_operation(operation)
operation.apply(obj)
return obj
def _get_operation(self, operation):
if 'op' not in operation:
raise JsonPatchException("Operation does not contain 'op' member")
raise Exception
op = operation['op']
if op not in self.operations:
raise JsonPatchException("Unknown operation '%s'" % op)
cls = self.operations[op]
return cls(operation)
class PatchOperation(object):
"""A single operation inside a JSON Patch."""
def __init__(self, operation):
self.location = operation['path']
self.pointer = jsonpointer.JsonPointer(self.location)
self.operation = operation
def apply(self, obj):
"""Abstract method that applies patch operation to specified object."""
raise NotImplementedError('should implement patch operation.')
def __hash__(self):
return hash(frozenset(self.operation.items()))
def __eq__(self, other):
if not isinstance(other, PatchOperation):
return False
return self.operation == other.operation
class RemoveOperation(PatchOperation):
"""Removes an object property or an array element."""
def apply(self, obj):
subobj, part = self.pointer.to_last(obj)
try:
del subobj[part]
except KeyError as ex:
raise JsonPatchConflict(str(ex))
class AddOperation(PatchOperation):
"""Adds an object property or an array element."""
def apply(self, obj):
value = self.operation["value"]
subobj, part = self.pointer.to_last(obj, None)
if isinstance(subobj, list):
if part == '-':
subobj.append(value)
elif part > len(subobj) or part < 0:
raise JsonPatchConflict("can't insert outside of list")
else:
subobj.insert(part, value)
elif isinstance(subobj, dict):
if part in subobj:
raise JsonPatchConflict("object '%s' already exists" % part)
subobj[part] = value
else:
raise JsonPatchConflict("can't add to type '%s'"
"" % subobj.__class__.__name__)
class ReplaceOperation(PatchOperation):
"""Replaces an object property or an array element by new value."""
def apply(self, obj):
value = self.operation["value"]
subobj, part = self.pointer.to_last(obj)
if isinstance(subobj, list):
if part > len(subobj) or part < 0:
raise JsonPatchConflict("can't replace outside of list")
elif isinstance(subobj, dict):
if not part in subobj:
raise JsonPatchConflict("can't replace non-existant object '%s'"
"" % part)
else:
raise JsonPatchConflict("can't replace in type '%s'"
"" % subobj.__class__.__name__)
subobj[part] = value
class MoveOperation(PatchOperation):
"""Moves an object property or an array element to new location."""
def apply(self, obj):
from_ptr = jsonpointer.JsonPointer(self.operation['from'])
subobj, part = from_ptr.to_last(obj)
value = subobj[part]
if from_ptr.contains(self.pointer):
raise JsonPatchException('Cannot move values into its own children')
RemoveOperation({'op': 'remove', 'path': self.operation['from']}).apply(obj)
AddOperation({'op': 'add', 'path': self.location, 'value': value}).apply(obj)
class TestOperation(PatchOperation):
"""Test value by specified location."""
def apply(self, obj):
try:
subobj, part = self.pointer.to_last(obj)
if part is None:
val = subobj
else:
val = self.pointer.walk(subobj, part)
except JsonPointerException as ex:
raise JsonPatchTestFailed(str(ex))
if 'value' in self.operation:
value = self.operation['value']
if val != value:
raise JsonPatchTestFailed('%s is not equal to tested value %s (types %s and %s)' % (val, value, type(val), type(value)))
class CopyOperation(PatchOperation):
""" Copies an object property or an array element to a new location """
def apply(self, obj):
from_ptr = jsonpointer.JsonPointer(self.operation['from'])
subobj, part = from_ptr.to_last(obj)
value = copy.deepcopy(subobj[part])
AddOperation({'op': 'add', 'path': self.location, 'value': value}).apply(obj)
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