python-json-patch/jsonpatch.py at master · graingert/python-json-patch · GitHub

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# -*- coding: utf-8 -*-

# python-json-patch - An implementation of the JSON Patch format

# https://github.com/stefankoegl/python-json-patch

# 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 (RFC 6902) """

from __future__ import unicode_literals

import collections

import copy

import functools

import inspect

import json

import sys

from jsonpointer import JsonPointer, JsonPointerException

# Will be parsed by setup.py to determine package metadata

__author__ = 'Stefan Kögl <stefan@skoegl.net>'

__version__ = '1.3'

__website__ = 'https://github.com/stefankoegl/python-json-patch'

__license__ = 'Modified BSD License'

# pylint: disable=E0611,W0404

if sys.version_info >= (3, 0):

basestring = (bytes, str) # pylint: disable=C0103,W0622

from itertools import zip_longest

else:

from itertools import izip_longest as zip_longest

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 multidict(ordered_pairs):

"""Convert duplicate keys values to lists."""

# read all values into lists

mdict = collections.defaultdict(list)

for key, value in ordered_pairs:

mdict[key].append(value)

return dict(

# unpack lists that have only 1 item

(key, values[0] if len(values) == 1 else values)

for key, values in mdict.items()

)

def get_loadjson():

""" adds the object_pairs_hook parameter to json.load when possible

The "object_pairs_hook" parameter is used to handle duplicate keys when

loading a JSON object. This parameter does not exist in Python 2.6. This

methods returns an unmodified json.load for Python 2.6 and a partial

function with object_pairs_hook set to multidict for Python versions that

support the parameter. """

argspec = inspect.getargspec(json.load)

if 'object_pairs_hook' not in argspec.args:

return json.load

return functools.partial(json.load, object_pairs_hook=multidict)

json.load = get_loadjson()

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'}

>>> patch = [{'op': 'add', 'path': '/baz', 'value': 'qux'}]

>>> other = apply_patch(doc, patch)

>>> doc is not other

True

>>> other == {'foo': 'bar', 'baz': 'qux'}

True

>>> patch = [{'op': 'add', 'path': '/baz', 'value': 'qux'}]

>>> apply_patch(doc, patch, in_place=True) == {'foo': 'bar', 'baz': 'qux'}

True

>>> 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._ops))

def __eq__(self, other):

if not isinstance(other, JsonPatch):

return False

return self._ops == other._ops

def __ne__(self, other):

return not(self == other)

@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)

@property

def _ops(self):

return tuple(map(self._get_operation, 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._ops:

obj = operation.apply(obj)

return obj

def _get_operation(self, operation):

if 'op' not in operation:

raise JsonPatchException("Operation does not contain 'op' member")

op = operation['op']

if not isinstance(op, basestring):

raise JsonPatchException("Operation must be a string")

if op not in self.operations:

raise JsonPatchException("Unknown operation {0!r}".format(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(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

def __ne__(self, other):

return not(self == other)

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 IndexError as ex:

raise JsonPatchConflict(str(ex))

return obj

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)

if isinstance(subobj, list):

if part == '-':

subobj.append(value) # pylint: disable=E1103

elif part > len(subobj) or part < 0:

raise JsonPatchConflict("can't insert outside of list")

else:

subobj.insert(part, value) # pylint: disable=E1103

elif isinstance(subobj, dict):

if part is None:

obj = value # we're replacing the root

else:

subobj[part] = value

else:

raise TypeError("invalid document type {0}".format(type(subobj)))

return obj

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 part is None:

return value

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:

msg = "can't replace non-existent object '{0}'".format(part)

raise JsonPatchConflict(msg)

else:

raise TypeError("invalid document type {0}".format(type(subobj)))

subobj[part] = value

return obj

class MoveOperation(PatchOperation):

"""Moves an object property or an array element to new location."""

def apply(self, obj):

from_ptr = JsonPointer(self.operation['from'])

subobj, part = from_ptr.to_last(obj)

value = subobj[part]

if self.pointer.contains(from_ptr):

raise JsonPatchException('Cannot move values into its own children')

obj = RemoveOperation({

'op': 'remove',

'path': self.operation['from']

}).apply(obj)

obj = AddOperation({

'op': 'add',

'path': self.location,

'value': value

}).apply(obj)

return 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:

msg = '{0} ({1}) is not equal to tested value {2} ({3})'

raise JsonPatchTestFailed(msg.format(val, type(val),

value, type(value)))

return obj

class CopyOperation(PatchOperation):

""" Copies an object property or an array element to a new location """

def apply(self, obj):

from_ptr = JsonPointer(self.operation['from'])

subobj, part = from_ptr.to_last(obj)

value = copy.deepcopy(subobj[part])

obj = AddOperation({

'op': 'add',

'path': self.location,

'value': value

}).apply(obj)

return obj

python-json-patch/jsonpatch.py at master · graingert/python-json-patch · GitHub

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