303 lines
10 KiB
Python
303 lines
10 KiB
Python
# -*- coding: utf-8 -*-
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#
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# python-json-patch - An implementation of the JSON Patch format
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# https://github.com/stefankoegl/python-json-patch
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#
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# Copyright (c) 2011 Stefan Kögl <stefan@skoegl.net>
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. The name of the author may not be used to endorse or promote products
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# derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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"""Apply JSON-Patches according to
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http://tools.ietf.org/html/draft-pbryan-json-patch-04"""
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# Will be parsed by setup.py to determine package metadata
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__author__ = 'Stefan Kögl <stefan@skoegl.net>'
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__version__ = '0.1'
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__website__ = 'https://github.com/stefankoegl/python-json-patch'
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__license__ = 'Modified BSD License'
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import json
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class JsonPatchException(Exception):
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"""Base Json Patch exception"""
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class JsonPatchConflict(JsonPatchException):
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"""Raises if patch could be applied due to conflict situations such as:
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- attempt to add object key then it already exists;
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- attempt to operate with nonexistence object key;
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- attempt to insert value to array at position beyond of it size;
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- etc.
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"""
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def apply_patch(doc, patch):
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"""Apply list of patches to specified json document.
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>>> doc = {'foo': 'bar'}
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>>> other = apply_patch(doc, [{'add': '/baz', 'value': 'qux'}])
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>>> doc is other
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True
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>>> doc
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{'foo': 'bar', 'baz': 'qux'}
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"""
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patch = JsonPatch(patch)
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return patch.apply(doc)
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def make_patch(src, dst):
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"""Generates patch by comparing of two objects.
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>>> src = {'foo': 'bar', 'numbers': [1, 3, 4, 8]}
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>>> dst = {'baz': 'qux', 'numbers': [1, 4, 7]}
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>>> patch = make_patch(src, dst)
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>>> patch.apply(src) #doctest: +ELLIPSIS
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{...}
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>>> src == dst
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True
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"""
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def compare_values(path, value, other):
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if isinstance(value, dict) and isinstance(other, dict):
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for operation in compare_dict(path, value, other):
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yield operation
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elif isinstance(value, list) and isinstance(other, list):
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for operation in compare_list(path, value, other):
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yield operation
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else:
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yield {'replace': '/'.join(path), 'value': other}
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def compare_dict(path, src, dst):
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for key in src:
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if key not in dst:
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yield {'remove': '/'.join(path + [key])}
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elif src[key] != dst[key]:
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current = path + [key]
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for operation in compare_values(current, src[key], dst[key]):
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yield operation
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for key in dst:
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if key not in src:
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yield {'add': '/'.join(path + [key]), 'value': dst[key]}
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def compare_list(path, src, dst):
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lsrc, ldst = len(src), len(dst)
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for idx in reversed(xrange(max(lsrc, ldst))):
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if idx < lsrc and idx < ldst:
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current = path + [str(idx)]
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for operation in compare_values(current, src[idx], dst[idx]):
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yield operation
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elif idx < ldst:
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yield {'add': '/'.join(path + [str(idx)]),
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'value': dst[idx]}
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elif idx < lsrc:
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yield {'remove': '/'.join(path + [str(idx)])}
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return JsonPatch(list(compare_dict([''], src, dst)))
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class JsonPatch(object):
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"""A JSON Patch is a list of Patch Operations.
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>>> patch = JsonPatch([
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... {'add': '/foo', 'value': 'bar'},
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... {'add': '/baz', 'value': [1, 2, 3]},
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... {'remove': '/baz/1'},
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... {'test': '/baz', 'value': [1, 3]},
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... {'replace': '/baz/0', 'value': 42},
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... {'remove': '/baz/1'},
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... ])
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>>> doc = {}
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>>> patch.apply(doc)
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{'foo': 'bar', 'baz': [42]}
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"""
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def __init__(self, patch):
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self.patch = patch
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self.operations = {
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'remove': RemoveOperation,
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'add': AddOperation,
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'replace': ReplaceOperation,
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'move': MoveOperation,
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'test': TestOperation
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}
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def __str__(self):
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"""str(self) -> self.to_string()"""
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return self.to_string()
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@classmethod
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def from_string(cls, patch_str):
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"""Creates JsonPatch instance from string source."""
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patch = json.loads(patch_str)
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return cls(patch)
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def to_string(self):
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"""Returns patch set as JSON string."""
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return json.dumps(self.patch)
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def apply(self, obj):
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"""Applies the patch to given object."""
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for operation in self.patch:
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operation = self._get_operation(operation)
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operation.apply(obj)
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return obj
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def _get_operation(self, operation):
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for action, op_cls in self.operations.items():
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if action in operation:
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location = operation[action]
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return op_cls(location, operation)
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raise JsonPatchException("invalid operation '%s'" % operation)
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class PatchOperation(object):
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"""A single operation inside a JSON Patch."""
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def __init__(self, location, operation):
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self.location = location
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self.operation = operation
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def apply(self, obj):
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"""Abstract method that applies patch operation to specified object."""
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raise NotImplementedError('should implement patch operation.')
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def locate(self, obj, location, last_must_exist=True):
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"""Walks through the object according to location.
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Returns the last step as (sub-object, last location-step)."""
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parts = location.split('/')
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if parts.pop(0) != '':
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raise JsonPatchException('location must starts with /')
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for part in parts[:-1]:
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obj, _ = self._step(obj, part)
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_, last_loc = self._step(obj, parts[-1], must_exist=last_must_exist)
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return obj, last_loc
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def _step(self, obj, loc_part, must_exist=True):
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"""Goes one step in a locate() call."""
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if isinstance(obj, dict):
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part_variants = [loc_part]
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for variant in part_variants:
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if variant not in obj:
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continue
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return obj[variant], variant
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elif isinstance(obj, list):
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part_variants = [int(loc_part)]
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for variant in part_variants:
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if variant >= len(obj):
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continue
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return obj[variant], variant
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else:
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raise ValueError('list or dict expected, got %r' % type(obj))
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if must_exist:
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raise JsonPatchConflict('key %s not found' % loc_part)
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else:
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return obj, part_variants[0]
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class RemoveOperation(PatchOperation):
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"""Removes an object property or an array element."""
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def apply(self, obj):
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subobj, part = self.locate(obj, self.location)
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del subobj[part]
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class AddOperation(PatchOperation):
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"""Adds an object property or an array element."""
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def apply(self, obj):
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value = self.operation["value"]
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subobj, part = self.locate(obj, self.location, last_must_exist=False)
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if isinstance(subobj, list):
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if part > len(subobj) or part < 0:
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raise JsonPatchConflict("can't insert outside of list")
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subobj.insert(part, value)
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elif isinstance(subobj, dict):
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if part in subobj:
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raise JsonPatchConflict("object '%s' already exists" % part)
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subobj[part] = value
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else:
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raise JsonPatchConflict("can't add to type '%s'"
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"" % subobj.__class__.__name__)
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class ReplaceOperation(PatchOperation):
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"""Replaces an object property or an array element by new value."""
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def apply(self, obj):
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value = self.operation["value"]
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subobj, part = self.locate(obj, self.location)
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if isinstance(subobj, list):
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if part > len(subobj) or part < 0:
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raise JsonPatchConflict("can't replace outside of list")
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elif isinstance(subobj, dict):
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if not part in subobj:
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raise JsonPatchConflict("can't replace non-existant object '%s'"
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"" % part)
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else:
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raise JsonPatchConflict("can't replace in type '%s'"
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"" % subobj.__class__.__name__)
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subobj[part] = value
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class MoveOperation(PatchOperation):
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"""Moves an object property or an array element to new location."""
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def apply(self, obj):
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subobj, part = self.locate(obj, self.location)
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value = subobj[part]
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RemoveOperation(self.location, self.operation).apply(obj)
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AddOperation(self.operation['to'], {'value': value}).apply(obj)
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class TestOperation(PatchOperation):
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"""Test value by specified location."""
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def apply(self, obj):
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value = self.operation['value']
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subobj, part = self.locate(obj, self.location)
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assert subobj[part] == value
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