proposal: encoding/json.Encoder: add ZeroizeNilSlice option

[zyxkad]

What does it do

Use (*json.Encoder).SetZeroizeNilSlice(true) can let the encoder encode nil slice as an empty json array [] instead of null

Why

If we have a nil slive []Type(nil), the encoder will encode it as null. Then the consumers will having trouble with it, they must to check if the field is null first.
A way to solve this problem is always alloc a zero length slice before encoding. However, I want my code be simplify but not fill with make([]Type, 0) every where.

Additional Information

1. This change should be completely backward compatible.
2. The options name is not good, maybe have to decide a better name later.

[arp242]

Also: #27589, #37711, probably a few others

[arp242]

Searching for "encoding/json" in the title with the "proposal" tag narrows it down a good bit: https://github.com/golang/go/issues?q=is%3Aissue+%22encoding%2Fjson%22+in%3Atitle+label%3Aproposal+sort%3Areactions-%2B1-desc

[mvdan]

I'm going to close this as a duplicate, since there isn't any new information in this thread compared to the older ones.

[zyxkad]

I'm going to close this as a duplicate, since there isn't any new information in this thread compared to the older ones.

Hm, well, I don't think so. The two issues arp242 mentioned is about struct tags, but mines is about Encoder options.
@mvdan

[mvdan]

Sure, I'll reopen. Just note that the proposals seem identical other than the method for opting into the behavior. That's probably one of the most important design characteristics, but ideally we wouldn't have multiple threads due to it.