json_object_merge does not merge

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "json.h"
#include "json-builder.h"

#define R(x...) #x

int main()
{
    const char *json1 = R({"x": 1, "y": 2});
    const char *json2 = R({"y": 3, "z": 4});

    char error[128];
    json_settings settings = {};
    settings.value_extra = json_builder_extra;
    json_value *obj1 = json_parse_ex(&settings, json1, strlen(json1), error);
    json_value *obj2 = json_parse_ex(&settings, json2, strlen(json1), error);

    json_object_merge(obj1, obj2);

    char *buf = malloc(json_measure(obj1));
    json_serialize(buf, obj1);

    printf("buf: `%s'\n", buf);
    return 0;
}

buf: `, "z": 4{ "y": 3, "z": 4 }'

That's odd, isn't it? I think, I was supposed to get {"x": 1, "y": 3, "z": 4"} here. Maybe the function should be rewritten completely using the recursive scheme. I suppose, it must be good to have an ability to merge e.g.

{"arr": [{"id": "1", "data": "A"}, {"id": "2", "data": "B"}]} <+>
{"arr": [{"id": "1", "extra": "@"}, {"id": "2", "data": "Z"}, {"id": "C"}]} ==
{"arr": [{"id": "1", "data": "A", "extra": "@"}, {"id": "2", "data": "Z"}, {"id": "3"}]}

I'll try to take a look on the sources in a couple of days and figure it out.

[jamesamcl]

Yep that's not right at all - merge must be producing a malformed object to get that output from serialize.

I'll check it out this evening.

[jamesamcl]

Currently, the expected output from merge for that example would be {"x": 1, "y": 2, "y": 3, "z": 4}. Which is obviously not ideal, but it's O(n). I would also be interested in being able to get {"x": 1, "y": 2, "z": 4}, but that would be O(n^2) because it would have to search through the existing keys for each key added.

Perhaps I could rename the existing json_object_merge to json_object_extend (because it basically does the same thing as jQuery's extend), and add a flag to indicate whether to allow duplicate keys in the resulting object or (more expensively) replace any existing properties. Then a recursive, deep json_object_merge could be added with the behaviour you describe.

[jamesamcl]

As of e766b23, the output is { "x": 1, "y": 2, "y": 3, "z": 4 }. Tomorrow I'll have a look at renaming this to extend and adding the flag to allow/disallow duplicate keys, and then a real merge function can be added at some point.

I just noticed in your example: it doesn't matter in this case because the JSON snippets are the same length, but both of your json_parse_ex calls use strlen(json1). Cool trick with the R(...) macro by the way.

Oh, that's great news! Thank you. Yep, this is a dummy copy-n-paste error, thanks for noticing.