Serde 0.8.0

[dtolnay]

Issue for tracking and discussion related to the upcoming 0.8.0 release.

Let's all do a thorough read through the entire public API and see if there is anything we do not want to live with for the next several months.

The big ticket items remaining are:

• Various bounds-related codegen issues which are all secretly the same issue Only emit bounds that contain type parameters #436 overflow evaluating the requirement test_ser::Outer: test_annotations::serde::Serialize #441 derive(Serialize) regression with lifetimes #443. This is next on my list.
• Remove default implementations from the Deserializer trait as per Serializer and Deserializer should be pure interface #219. This is a lot of tedious work because we have 17 implementations in the codebase and Deserializer has 31 methods.
• Look at existing Deserializer implementations across GitHub and see whether there are any common helpers that would be good for us to own, like we do with all of these.
• Decide what to do about Fields marked skip_deserializing are ignored even if deny_unknown_fields is set #444. It may or may not require a breaking change - if not, it can wait.

Aside from that, now is a good time for documentation improvements and code cleanup as many developers will be looking at docs as they migrate from 0.7.

[oli-obk]

This is a lot of tedious work because we have 17 implementations in the codebase and Deserializer has 31 methods. Let's also look at existing Deserializer implementations across GitHub and see whether there are any common helpers

is it possible to specify a macro that takes method names as arguments and produces the default methods?

[dtolnay]

is it possible to specify a macro that takes method names as arguments and produces the default methods?

Yes, for internal use but we need to be very careful about what we make public. The reason for removing the defaults was because it is hard to know what makes a good default for a "typical" Deserializer.

[dtolnay]

Here is what adoption looks like so far (not counting the 100+ google APIs which are really one project):

     54 ^0.7
     34 ^0.7.0
     21 ^0.6
     13 ^0.7.10
      8 ^0.8.0
      5 ^0.7.5
      5 ~0.7
      5 *
      4 ^0.7.11
      4 ~0.7.0
      3 ^0.7.9
      3 ^0.6.13
      3 >= 0.6, < 0.8
      2 ^0.8
      2 ^0.7.14
      2 ^0.6.7
      2 ^0.6.6
      2 ^0.6.11
      2 >= 0.6.1, < 0.8
      2 ~0.6.1
      2 ^0.6.0
      1 0.8.*
      1 = 0.7.9
      1 ^0.7.7
      1 ^0.7.6
      1 ~0.7.5
      1 ^0.7.15
      1 ^0.7.13
      1 0.7.*
      1 >= 0.6.6, < 0.8
      1 ^0.6.14
      1 ^0.6.10
      1 0.6.*
      1 ^0.5.3
      1 >= 0.5.0
      1 ^0.4.2
      1 ^0.4

The early adopters are:

bincode
ruma-identifiers
rust_cast
serde_json
serde_macros
serde-pickle
serde_test
serde_xml
serde_yaml
socket-io
tarpc

So 5 so far not counting the ones @oli-obk and I did.

[jimmycuadra]

ruma-events is also using it, but not published to crates.io. Everything is working splendidly so far.