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✨ implemented JSON Merge Patch (RFC 7396)

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SQLite's json1 extension (https://www.sqlite.org/json1.html) supports JSON Merge Patch (https://tools.ietf.org/html/rfc7396). As the implementation is trivial and we already support JSON Patch, I think this could be a nice extension to the library.
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Niels Lohmann 2017-12-13 23:36:22 +01:00
parent f7ae143a93
commit c6e7eae394
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40
doc/examples/merge_patch.cpp Normal file
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@ -0,0 +1,40 @@
#include <iostream>
#include "json.hpp"
#include <iomanip> // for std::setw
using json = nlohmann::json;
int main()
{
// the original document
json document = R"({
"title": "Goodbye!",
"author": {
"givenName": "John",
"familyName": "Doe"
},
"tags": [
"example",
"sample"
],
"content": "This will be unchanged"
})"_json;
// the patch
json patch = R"({
"title": "Hello!",
"phoneNumber": "+01-123-456-7890",
"author": {
"familyName": null
},
"tags": [
"example"
]
})"_json;
// apply the patch
document.merge_patch(patch);
// output original and patched document
std::cout << std::setw(4) << document << std::endl;
}

1
doc/examples/merge_patch.link Normal file
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@ -0,0 +1 @@
<a target="_blank" href="https://wandbox.org/permlink/h13IsbffwmMfqsej"><b>online</b></a>

11
doc/examples/merge_patch.output Normal file
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@ -0,0 +1,11 @@
{
"author": {
"givenName": "John"
},
"content": "This will be unchanged",
"phoneNumber": "+01-123-456-7890",
"tags": [
"example"
],
"title": "Hello!"
}

79
src/json.hpp
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@ -14165,6 +14165,7 @@ class basic_json
diff for two JSON values.,diff}
@sa @ref patch -- apply a JSON patch
@sa @ref merge_patch -- apply a JSON Merge Patch
@sa [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
@ -14296,6 +14297,84 @@ class basic_json
}
/// @}
////////////////////////////////
// JSON Merge Patch functions //
////////////////////////////////
/// @name JSON Merge Patch functions
/// @{
/*!
@brief applies a JSON Merge Patch
The merge patch format is primarily intended for use with the HTTP PATCH
method as a means of describing a set of modifications to a target
resource's content. This function applies a merge patch to the current
JSON value.
The function implements the following algorithm from Section 2 of
[RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396):
```
define MergePatch(Target, Patch):
if Patch is an Object:
if Target is not an Object:
Target = {} // Ignore the contents and set it to an empty Object
for each Name/Value pair in Patch:
if Value is null:
if Name exists in Target:
remove the Name/Value pair from Target
else:
Target[Name] = MergePatch(Target[Name], Value)
return Target
else:
return Patch
```
Thereby, `Target` is the current object; that is, the patch is applied to
the current value.
@param[in] patch the patch to apply
@complexity Linear in the lengths of @a patch.
@liveexample{The following code shows how a JSON Merge Patch is applied to
a JSON document.,merge_patch}
@sa @ref patch -- apply a JSON patch
@sa [RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396)
@since version 3.0.0
*/
void merge_patch(const basic_json& patch)
{
if (patch.is_object())
{
if (not is_object())
{
*this = object();
}
for (auto it = patch.begin(); it != patch.end(); ++it)
{
if (it.value().is_null())
{
erase(it.key());
}
else
{
operator[](it.key()).merge_patch(it.value());
}
}
}
else
{
*this = patch;
}
}
/// @}
};
/////////////

1
test/Makefile
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@ -28,6 +28,7 @@ SOURCES = src/unit.cpp \
src/unit-iterator_wrapper.cpp \
src/unit-iterators1.cpp \
src/unit-iterators2.cpp \
src/unit-merge_patch.cpp \
src/unit-json_patch.cpp \
src/unit-json_pointer.cpp \
src/unit-meta.cpp \

261
test/src/unit-merge_patch.cpp Normal file
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/*
__ _____ _____ _____
__| | __| | | | JSON for Modern C++ (test suite)
| | |__ | | | | | | version 2.1.1
|_____|_____|_____|_|___| https://github.com/nlohmann/json
Licensed under the MIT License <http://opensource.org/licenses/MIT>.
Copyright (c) 2013-2017 Niels Lohmann <http://nlohmann.me>.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
#include "catch.hpp"
#include "json.hpp"
using nlohmann::json;
TEST_CASE("JSON Merge Patch")
{
SECTION("examples from RFC 7396")
{
SECTION("Section 1")
{
json document = R"({
"a": "b",
"c": {
"d": "e",
"f": "g"
}
})"_json;
json patch = R"({
"a": "z",
"c": {
"f": null
}
})"_json;
json expected = R"({
"a": "z",
"c": {
"d": "e"
}
})"_json;
document.merge_patch(patch);
CHECK(document == expected);
}
SECTION("Section 3")
{
json document = R"({
"title": "Goodbye!",
"author": {
"givenName": "John",
"familyName": "Doe"
},
"tags": [
"example",
"sample"
],
"content": "This will be unchanged"
})"_json;
json patch = R"({
"title": "Hello!",
"phoneNumber": "+01-123-456-7890",
"author": {
"familyName": null
},
"tags": [
"example"
]
})"_json;
json expected = R"({
"title": "Hello!",
"author": {
"givenName": "John"
},
"tags": [
"example"
],
"content": "This will be unchanged",
"phoneNumber": "+01-123-456-7890"
})"_json;
document.merge_patch(patch);
CHECK(document == expected);
}
SECTION("Appendix A")
{
SECTION("Example 1")
{
json original = R"({"a":"b"})"_json;
json patch = R"({"a":"c"})"_json;
json result = R"({"a":"c"})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 2")
{
json original = R"({"a":"b"})"_json;
json patch = R"({"b":"c"})"_json;
json result = R"({"a":"b", "b":"c"})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 3")
{
json original = R"({"a":"b"})"_json;
json patch = R"({"a":null})"_json;
json result = R"({})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 4")
{
json original = R"({"a":"b","b":"c"})"_json;
json patch = R"({"a":null})"_json;
json result = R"({"b":"c"})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 5")
{
json original = R"({"a":["b"]})"_json;
json patch = R"({"a":"c"})"_json;
json result = R"({"a":"c"})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 6")
{
json original = R"({"a":"c"})"_json;
json patch = R"({"a":["b"]})"_json;
json result = R"({"a":["b"]})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 7")
{
json original = R"({"a":{"b": "c"}})"_json;
json patch = R"({"a":{"b":"d","c":null}})"_json;
json result = R"({"a": {"b": "d"}})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 8")
{
json original = R"({"a":[{"b":"c"}]})"_json;
json patch = R"({"a":[1]})"_json;
json result = R"({"a":[1]})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 9")
{
json original = R"(["a","b"])"_json;
json patch = R"(["c","d"])"_json;
json result = R"(["c","d"])"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 10")
{
json original = R"({"a":"b"})"_json;
json patch = R"(["c"])"_json;
json result = R"(["c"])"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 11")
{
json original = R"({"a":"foo"})"_json;
json patch = R"(null)"_json;
json result = R"(null)"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 12")
{
json original = R"({"a":"foo"})"_json;
json patch = R"("bar")"_json;
json result = R"("bar")"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 13")
{
json original = R"({"e":null})"_json;
json patch = R"({"a":1})"_json;
json result = R"({"e":null,"a":1})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 14")
{
json original = R"([1,2])"_json;
json patch = R"({"a":"b","c":null})"_json;
json result = R"({"a":"b"})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
SECTION("Example 15")
{
json original = R"({})"_json;
json patch = R"({"a":{"bb":{"ccc":null}}})"_json;
json result = R"({"a":{"bb":{}}})"_json;
original.merge_patch(patch);
CHECK(original == result);
}
}
}
}