Don't sort JSON keys in the Web API

[fpagnoux]

By default, FLASK sorts the JSON keys of the API responses. This PR opts out of this behavior.

In some use-cases (merge with IPP parameters in France), having the same orders in API responses that in the parameter YAML files avoid extra work and boilerplate.

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Edit by @maukoquiroga 2018-12-09:

I'm ok with the fact that we don't order an object defined as unordered by the JSON specification. However, as discussed in the comments, I omitted any mention of use-case from the motivation of this PR's introduced changes.

[fpagnoux]

@Morendil this should allow to avoid the order keys in the IPP YAML parameters file.

[bonjourmauko]

Hi @fpagnoux, thanks for your contribution.

I'm convinced that, currently, this contribution is, or should be, backwards compatible: JSON schema isn't changed, and we can expect from users to do not expect JSON keys to be in any specific order, and to manage that by themselves.

Or, as I understand it, the use case described here implies that a client will be relying on a specific order of the served JSON keys.

That means that, from now on, any change to this behaviour will have to be considered de facto as a breaking-change.

So for now I'm personally against the merge of this contribution, and propose we close for the reasons exposed supra.

If you see any shortcomings on my reasoning, please challenge it. I'm also requesting other contributor's reviews to do so as well.

[fpagnoux]

Or, as I understand it, the use case described here implies that a client will be relying on a specific order of the served JSON keys.
That means that, from now on, any change to this behaviour will have to be considered de facto as a breaking-change.

Well, not really. If a client of your library decide to use an internal method of a class, it doesn't mean that this method becomes part of your interface. It means that your clients are taking a risk, and that's on them ;).

I think NodeJS de facto preserves dictionary insertion order. That's however not part of their API contract. Some people rely on that, even if it's not advised. That's a risk they are taking. Node warns against doing that, but Node doesn't shuffle the dictionary order just for the sake of it. This is what we are doing right now, and this PR just suggests to stop doing so, without any promise to the API user.

I haven't written the changelog yet, but I'd phrase it like "Do not alphabetically sort JSON keys in Web API response". Once again, no promise, and no contract.

Does this address your concern ?

[bonjourmauko]

@fpagnoux I edited the description