Convert output to serde_json::Value before printing

[smoelius]

This change causes map keys to be ordered alphabetically. An example appears below.

I'm not 100% sure of the reason for the difference. I suspect that without converting to a value, serde_json uses Serde machinery to traverse struct fields (e.g., PublisherData) in the order in which they are declared. Whereas, a serde_json::Objects's keys are always ordered alphabetically.

I would be happy to add a test. I would just need some direction on where an how to add it.

---

Without the change:

$ cargo supply-chain json --diffable
...
    "xdg": [
      {
        "id": 654,
        "login": "whitequark",
        "kind": "user",
        "name": "whitequark",
        "avatar": "https://avatars1.githubusercontent.com/u/54771?v=4"
      }
    ]
...

With the change:

$ cargo run -- supply-chain json --diffable
...
    "xdg": [
      {
        "avatar": "https://avatars1.githubusercontent.com/u/54771?v=4",
        "id": 654,
        "kind": "user",
        "login": "whitequark",
        "name": "whitequark"
      }
    ]
...

[Shnatsel]

I believe it's more efficient to rearrange struct fields to keep them alphabetical and serialize the data like that, instead of going through the serde_json::Value machinery. It would probably be a better idea to do that, if we can enforce it without too much trouble.

But why is an alphabetical ordering desirable in the first place?

[smoelius]

But why is an alphabetical ordering desirable in the first place?

To make diffing more predictable.

My guess about why things are ordered they way they currently are is just a guess. I haven't found anything in serde_json to explain the current behavior.

Also, FWIW, converting output to a serde_json::Value has other differences. For example, it moves not_audited to after crates_io_crates.

[Shnatsel]

Could you provide a specific example where it helps? Like, a specific tool, and show the diffs before and after?

I'd like to understand the exact effect of the changes to determine the best course of action.

[smoelius]

Here are the complete "before" and "after" for cargo-supply-chain itself:
before.json
after.json

I think having any imposed order helps. I haven't found it in the serde_json's documentation, but there is this comment from dtolnay:

Yeah, as long as you don't enable preserve_order then Value will always print with map keys sorted lexicographically.

Based on my understanding, there are no guarantees regarding the order of keys coming from non-Values, which makes diffing unpredictable.

Also, apologies. I should have opened an issue to rather than assume this change would be accepted.

[Shnatsel]

In practice the fields are printed in the declaration order. I understand that the fields are printed in a stable order, even if that order may appear arbitrary. So I don't see how this change would improve diffing.

I was hoping you could show me the JSON diffs before and after this change, and the diffs after would be clearly better somehow.

[smoelius]

I was hoping you could show me the JSON diffs before and after this change, and the diffs after would be clearly better somehow.

I don't think I can provide that.

Thanks for your consideration, and thanks for a great tool, which I use in several of my projects!

[Shnatsel]

Thank you for taking the time to open a PR anyway. And I'm glad you find the tool useful!