Can diff method ignore the array order?

[zhuda]

Hi, I am using the diff() method to compare two json files and would like to ignore the oder changes in array, is it possible?

group: {
    users: [
       {id: 234, name: John},
       {id: 345, name: Mike}
    ]
}

should be equal to:

group: {
    users: [
       {id: 345, name: Mike},
       {id: 234, name: John}
    ]
}

Thanks!

[nlohmann]

No, this is not possible. Best would be if you would sort the array yourself before calling diff.

[zhuda]

Thanks. I am new to JSON. Maybe I know this is a illegal request or this could be a reasonable enhancement?

[nlohmann]

I don't see the benefit for this, because the diff function should detect differences in the array element order. I think your usecase is rather specific.

[Bigpet]

Just for context ignoring the order of all arrays in the hierachy to find the minimal diff is computationally very expensive as soon as you nest a couple arrays.
If you don't set sensible constraints a couple of KB of json can take you minutes to diff.
One such library that tries to offer this is deepdiff and even if its default doesn't do a fully exhaustive search it aready took almost half an hour to process a real-world ca. 300KB json, not a constructed example.

(I know the whole "python is slow" stuff didn't help this case but the point remains that very pathological cases make it hard to compute in a bounded time)