Add a json_pretty macro

[irevoire]

Hello, I really like the crate, but when I’m embedding a lot of super small tests, it gets huge because the assert_json use the to_string_pretty function of serde_json, which takes a lot of lines for the most basics function.

I would like to have the choice to use the to_string or to_string_pretty, so here’s a first PR.
I’m afraid it’s a huge breaking, though since the assert_json_snapshot will break everywhere wdyt?

[mitsuhiko]

I don't want to change the to_json format but I'm happy to build a more compact JSON snapshot format. Do you have by any chance some reference inputs you want to snapshot so I can get an understanding of what you are trying to snapshot?

[irevoire]

I don't want to change the to_json format

Honestly, I don’t think we should, but I had no idea for a new name 😂
Maybe we should call the « more compact JSON » assert_json_inlined_snapshot?

I don't want to change the to_json format but I'm happy to build a more compact JSON snapshot format. Do you have by any chance some reference inputs you want to snapshot so I can get an understanding of what you are trying to snapshot?

I don’t have much to show rn, but basically, I’m going to write a lot of tests looking like that where I try to query one document. (that were sent as JSON initially).
https://github.com/meilisearch/meilisearch/blob/35a28294313872710fa25976f7d425fe7271f4eb/index-scheduler/src/index_scheduler.rs#L450

Also, as you can see, I’m currently using another snapshot function to use a smaller debug snapshot; that’s another addition I would like to do after this one.

[mitsuhiko]

I have already been thinking in the past to add a assert_compact_json! which uses a more compact representation. I wouldn't have gone as forcing a single line and no whitespace, but to run a prettification approach where certain values are permitted to stay in a single line in collections. I can play around with this.

[irevoire]

I guess it would make sense to have something like;

• A top-level array of objects will use one line per object (look like jsonlines and is easy to diff)
• A top-level object uses one line per field
• Everything else is on a single line

But IMO, if I see you use serde_json, I’ll only expect you to provide the to_string and to_string_pretty methods.
And if you develop something like that, I would expect it to be available as a third option like json_smart_pretty or something 🤔

[mitsuhiko]

Since insta is no longer using serde_json I have quite some freedom to modify the serialization behavior. The current JSON serializer is in json.rs and should be easy enough to customize for different whitespace behaviors.

[mitsuhiko]

I am closing this in favor of #288.