Add Serialize/Deserialize for std::ops::Bound<DateTime> and friends

[manifest]

Would be useful for serializing PostgreSQL time range data types: tsrange, tstzrange, daterange that are already supported by Diesel.

[quodlibetor]

Where does the Bound type come from?

Either way you ought to be at least partially unblocked by using serde's support for remote crates

[manifest]

Where does the Bound type come from?

Diesel implements PostgreSQL range data types as (Bound<T>, Bound<T>) where T: FromSql<ST, Pg> and it looks as a good solution for ranges in general.

Either way you ought to be at least partially unblocked by using serde's support for remote crates

Sure, but it would be great to have such feature right out of the box.

[quodlibetor]

I agree it would be nice. I think that this feature belongs in diesel, though, since diesel depends on chrono not the other way around.

[manifest]

I think about that as a support for serialization and deserialization for time ranges in general. Because Bound is a native data type for Rust, it seems as the best candidate for time ranges. I mean the type itself may be useful without Diesel.

[quodlibetor]

Ah, yes, when you responded that Bound was implemented by diesel I thought you meant that it was a diesel-defined type, but I believe you are referring to std::ops::Bound?

Implementation-wise, that seems straightforward. Currently the serde feature is guaranteed to work with rust 1.15, and Bound was only added in 1.17, so this should be behind a serde-bound feature flag until chrono 0.5.

A PR that implements that would be very welcome!

[manifest]

Yes, I was referring to std::ops::Bound.

[0nkery]

I think, there is no way (and no need, actually) to implement Serialize/Deserialize for Bound<DateTime> inside this crate.

Instead, this PR will allow to ser/de Bound<DateTime> when it will be merged - serde-rs/serde#1466.

We can close this issue, I guess?

[manifest]

We still need a few serde helpers (ts_seconds, etc) I believe.

[quodlibetor]

the serde helpers are only needed for the module helpers, which I don't think will be necessary for interacting with diesel's serde support.

I'm going to close this for now in favor of 0nkery's serde patches, but if those don't help enough then we can re-open or open a new, more specific, issue.