Add support for OpenTelemetry 0.21 #118
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src/lib.rs
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| #[cfg(all(feature = "opentelemetry_0_19", feature = "opentelemetry_0_20"))] | ||
| compile_error!("feature \"opentelemetry_0_19\" and feature \"opentelemetry_0_20\" cannot be enabled at the same time"); | ||
| const _OTEL_GUARD: () = assert!({ |
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It breaks it.
I don't see the error while building
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I think it's because compiler fails earlier than running/replacing consts.
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No, it's not runtime, const _: () forces compile-time evaluation of a const block here.
It might be a later compiler pass than checking import name clashes, so errors look different, but this will prevent compilation from working.
See https://internals.rust-lang.org/t/nicer-static-assertions/15986
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Anyway, compilation will fail, even if you remove this bit.
Having assert is as useful as not having it. But compile_error will be triggered earlier.
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Okay, I can revert this if that's your preference, however I don't think maintaining an ever-expanding and quite a bit error prone Cartesian cross-product of possible flag combinations is a good approach.
Ideally, there could be some macro that would take a feature list and then construct the cross product for us, but I'm unaware of such a macro and then whether it's at all possible as cfg! and #[cfg(..)] expression are a bit magical and might be evaluated earlier than any possible macro could kick in.
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If @LukeMathWalker agrees, we can use https://crates.io/crates/mutually_exclusive_features
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Happy to add the dependency!
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If @LukeMathWalker agrees, we can use https://crates.io/crates/mutually_exclusive_features
Cool, done. Is the @recurs [params: ...] a common convention for recursive declarative macros BTW? Haven't seen it yet.
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I'm not sure how common it is. I learned that from diesel macros, eg.
It's not just for recursion, they can there to make it rarely possible to being called from outside, and make internal calls in macros.
Like here, I used it, to name and extract a functionality of making comma separated list of items, with the comma_sep name. (And yes, in this case we also have a recursion and an extra rule for the last element.)
And about the new changes, I think we need exactly one of the opentelemetry_* features, no? I'm not sure. If so, then better to use exactly_one_of macro.
Issue #, if available:
Description of changes:
Adds support for OpenTelemetry 0.21. Nothing particularly interesting. While here, getting rid of the Fibonacci-exploding number of compile guards and use a single const-evaluated expression.
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