Expose rkyv features as features for chrono users.

[gz]

rkyv by default serializes usize as u32. This isn't ideal on most modern platforms and unfortunately is configured through a feature flag.

If we just set default-features = false in the rkyv Cargo dependency, the crate fails to compile because all the size features are mutually exclusive. On the other hand if we want to e.g., change the serialization of usize to 64-bit and we also want to use chrono this currently fails to compile because chrono always enables rkyv/size_32.

This re-exports the relevant rkyv features so users can choose which serialization to enable. The approach is similar to what the ordered-float crate does:

https://github.com/reem/rust-ordered-float/blob/8111b345372632893af0b8aa12152f3dc7278aba/Cargo.toml#L37

Note aside: rkyv with `default-features = false is what was recommended on the rkyv discord by the maintainer (see screenshot below). But it seems that the approach ordered-float took is better as it doesn't break backward compatibility (and compilation of chrono library without specifying any features).

Thanks for contributing to chrono!

If your feature is semver-compatible, please target the 0.4.x branch;
the main branch will be used for 0.5.0 development going forward.

Please consider adding a test to ensure your bug fix/feature will not break in the future.

[djc]

This makes sense to me, thanks!

If you want to use this any time soon, I recommend retargeting the PR/rebasing the branch on 0.4.x.

[gz]

Thanks for the review, I updated this and also made some changes to CI scripts to account for the fact that --all-features no longer works out of the box in a new commit.

[gz]

If you want to use this any time soon, I recommend retargeting the PR/rebasing the branch on 0.4.x.

Is there a timeline for the 0.5 release? I'm happy to send a PR for 0.4 if you think the 0.5 release is still a few months out.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d7b4a82) 91.64% compared to head (70dfc07) 91.67%.

Additional details and impacted files

@@            Coverage Diff             @@
##            0.4.x    #1368      +/-   ##
==========================================
+ Coverage   91.64%   91.67%   +0.02%     
==========================================
  Files          38       38              
  Lines       17554    17577      +23     
==========================================
+ Hits        16088    16113      +25     
+ Misses       1466     1464       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[gz]

Looks like the last test-failure I get is

Run cargo test --lib \
error: failed to parse manifest at `/home/runner/work/chrono/chrono/Cargo.toml`

Caused by:
  namespaced features with the `dep:` prefix are only allowed on the nightly channel and requires the `-Z namespaced-features` flag on the command-line
Error: Process completed with exit code 101.

and it's due to https://github.com/chronotope/chrono/pull/1368/files#diff-2e9d962a08321605940b5a657135052fbcef87b5e360662bb527c96d9a615542R37

I added it due to the suggestion here:

I propose that we instead use an rkyv-any (open to better naming suggestions) feature that is enabled by all the size features (add a comment that it is for internal use only, maybe?).

I'm not quite sure if it's possible to specify the feature with the same intent without using dep:? The alternatives are to go back to the uglier any(f1, f2, f3) approach or raise msrv to 1.60 (which is when this was stabilized). Any preferences on how to proceed?

[djc]

Is there a timeline for the 0.5 release? I'm happy to send a PR for 0.4 if you think the 0.5 release is still a few months out.

There is not, you definitely want to be on 0.4.x for now (and we do regular merges from 0.4.x -> main), so please just retarget this PR.

[djc]

I'm not quite sure if it's possible to specify the feature with the same intent without using dep:? The alternatives are to go back to the uglier any(f1, f2, f3) approach or raise msrv to 1.60 (which is when this was stabilized). Any preferences on how to proceed?

I think it is possible, just replace dep:rkyv with rkyv.

[gz]

@djc I rebased it on the 0.4 branch

[djc]

Thanks!

[pitdicker]

This PR was a breaking change, chrono no longer builds with just features = ["rkyv"] as reported in #1380.

This breaks our build on docs.rs for 0.4.32, although that is easy to fix.