Expose a way to serialize a KV with any Serde Serializer

[nightkr]

This is useful if you need to serialize to a more structured form, such as sending full JSON blobs to a HTTP endpoint.

[ncalexan]

Hey! I came here to file a ticket saying "make it easier to log inline JSON, i.e., serde structs as log values". Since there seems to be lots of conflicting information and questions about how to do this on the web (several threads in gitter, for example) I made https://github.com/ncalexan/slog-nested-values-example to work out what I needed to do. But I think your PR would do this and a little more. Is that correct? Can we get some discussion of this?

I would definitely like to see an example and/or tests of this functionality, 'cuz it's not obvious that it exists without examples :)

[nightkr]

@ncalexan This PR is for dumping log messages into arbitrary Serde Serializers (that is, output formats). If I understand you correctly, what you want is to be able to use Serde Serializes (serializable objects) as slog Values, which is more or less going the opposite way, and already works (as your example demonstrates).

[ncalexan]

@ncalexan This PR is for dumping log messages into arbitrary Serde Serializers (that is, output formats). If I understand you correctly, what you want is to be able to use Serde Serializes (serializable objects) as slog Values, which is more or less going the opposite way, and already works (as your example demonstrates).

Ah, I see -- I misunderstood the role of SerdeSerializer. I will open a new ticket. Thanks, @teozkr!

[dpc]

So, do I close this one?

[nightkr]

@dpc Well, the PR is still relevant and exposes functionality that slog-json doesn't have otherwise. I should just have explained it better in the original body.

[dpc]

Do you think we can get away without it? Unless there's a really good reason, would rather not have these couple of folks stuck with older compiler or something, have to upgrade.

[nightkr]

Absolutely. That's why I split the PR into cf7d07a (which adds the new serialize function) and e0a0f69 (which upgrades to 2018 without changing any functionality).