Expose rkyv features as features for chrono users.

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

Signed-off-by: Gerd Zellweger <mail@gerdzellweger.com>

Cargo.toml

@@ -17,6 +17,7 @@ rust-version = "1.61.0"
 name = "chrono"
 
 [features]
+# Don't forget to adjust `ALL_NON_EXCLUSIVE_FEATURES` in CI scripts when adding a feature or an optional dependency.
 default = ["clock", "std", "oldtime", "wasmbind"]
 alloc = []
 libc = []
@@ -27,15 +28,20 @@ now = ["std"]
 oldtime = []
 wasmbind = ["wasm-bindgen", "js-sys"]
 unstable-locales = ["pure-rust-locales"]
-rkyv-validation = ["rkyv/validation"]
+# Note that rkyv-16, rkyv-32, and rkyv-64 are mutually exclusive.
+rkyv-16 = ["rkyv", "rkyv?/size_16"]
+rkyv-32 = ["rkyv", "rkyv?/size_32"]
+rkyv-64 = ["rkyv", "rkyv?/size_64"]
+rkyv-validation = ["rkyv?/validation"]
+# Features for internal use only:
 __internal_bench = []
 
 [dependencies]
 num-traits = { version = "0.2", default-features = false }
 rustc-serialize = { version = "0.3.20", optional = true }
 serde = { version = "1.0.99", default-features = false, optional = true }
 pure-rust-locales = { version = "0.7", optional = true }
-rkyv = { version = "0.7.41", optional = true }
+rkyv = { version = "0.7.43", optional = true, default-features = false }
 arbitrary = { version = "1.0.0", features = ["derive"], optional = true }
 
 [target.'cfg(all(target_arch = "wasm32", not(any(target_os = "emscripten", target_os = "wasi"))))'.dependencies]

src/month.rs

@@ -33,7 +33,7 @@ use crate::OutOfRange;
 #[cfg_attr(feature = "rkyv", derive(Archive, Deserialize, Serialize))]
 #[cfg_attr(
     feature = "rkyv",
-    archive(compare(PartialEq)),
+    archive(compare(PartialEq, PartialOrd)),
     archive_attr(derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash))
 )]
 #[cfg_attr(feature = "rkyv-validation", archive(check_bytes))]

src/naive/isoweek.rs

@@ -20,7 +20,7 @@ use rkyv::{Archive, Deserialize, Serialize};
 #[cfg_attr(feature = "rkyv", derive(Archive, Deserialize, Serialize))]
 #[cfg_attr(
     feature = "rkyv",
-    archive(compare(PartialEq)),
+    archive(compare(PartialEq, PartialOrd)),
     archive_attr(derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash))
 )]
 #[cfg_attr(feature = "rkyv-validation", archive(check_bytes))]