backport recent changes to v0.1.x #2002
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## Motivation The `tracing`' crate's feature powerset is kind of unmanageably huge due to the large number of `max_level_XXX` and `release_max_level_XXX` feature flags. This is why we currently _don't_ run a `cargo-hack` feature powerset check for it on CI. However, I forgot about that when I added feature powerset checks to the `bin/publish` script, so publishing a `tracing` release results in a combinatorial explosion that takes a *very* long time to complete. ## Solution It turns out that `cargo-hack` actually has flags for controlling what features are included in the powerset (`--include-features` and `--exclude-features`). This branch modifies `bin/publish` to use those flags when checking the `tracing` and `tracing-subscriber` crate. Additionally, I've modified the CI `cargo-hack` job to use the same flags, so that it can now check `tracing` and `tracing-subscriber`. This allows us to remove the manual feature check jobs for those crates from CI. Signed-off-by: Eliza Weisman <[email protected]>
This branch removes some unnecessary uses of the `format_args!` and `write!` macros in `tracing-core`. Using `fmt::Display::fmt` and similar rather than the macros may be slightly more efficient. Co-authored-by: David Barsky <[email protected]>
davidbarsky
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Mar 18, 2022
## Motivation Currently, it is not actually possible to use `set_default(NoSubscriber)` or similar to temporarily disable the global default subscriber (see #1999). This is because `NoSubscriber` is currently used as a placeholder value when the thread-local cell that stores the current scoped default subscriber is initialized. Therefore, we currently check if the current scoped subscriber is `NoSubscriber`, and if it is, we fall back to returning the global default instead. This was fine, _when `NoSubscriber` was a private internal type only_. However, PR #1549 makes `NoSubscriber` into a public API type. When users can publicly construct `NoSubscriber` instances, it makes sense to want to be able to use `NoSubscriber` to disable the current subscriber. This is not possible when there is a global default set, because the local default being `NoSubscriber` will cause the global default to be returned. ## Solution This branch changes the thread-local cell to store an `Option<Dispatch>` instead, and use the `None` case to indicate no local default is set. This way, when the local default is explicitly set to `NoSubscriber`, we will return `NoSubscriber` rather than falling back. This may also be a slight performance improvement, because we now check if there's no global default by checking if the `Option` is `None`, rather than downcasting it to a `NoSubscriber`. I've also added a test reproducing #1999. Fixes #1999 Signed-off-by: Eliza Weisman <[email protected]>
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This branch backports the following changes:
format_args!andwrite!macros (Use less allocations in recordingDisplayandErrorvalues #1988)cargo-hack(chore: avoid giant feature powersets usingcargo-hack#1984)