subscriber: nicer `fmt::Debug` for `Layered` #1528

hawkw · 2021-08-30T17:31:27Z

Currently, Layered only implements fmt::Debug if the outer layer,
the inner layer, and the subscriber type parameters all implement
fmt::Debug. However, in the case of a Layered with two Layers, the
subscriber itself is not present --- it's only a PhantomData. So the
fmt::Debug implementation should be possible when only the actual
layer and inner values are Debug. For the PhantomData, we can
just print the type name.

This means that Layered consisting of two Layers and no Subscriber
will now implement Debug if the Layers are Debug, regardless of
the subscriber type. When the Layered is a Layer and a Subscriber,
the behavior will be the same, because the separate PhantomData
subscriber type param is always the same as the type of the inner
subscriber.

Because printing the whole type name of the subscriber is potentially
verbose (e.g. when the subscriber itself is a big pile of layers), we
only include it in alt-mode.

Currently, `Layered` only implements `fmt::Debug` if the outer layer, the inner layer, *and* the subscriber type parameters all implement `fmt::Debug`. However, in the case of a `Layered` with two `Layer`s, the subscriber itself is not present --- it's only a `PhantomData`. So the `fmt::Debug` implementation should be possible when only the actual `layer` and `inner` values are `Debug`. For the `PhantomData`, we can just print the type name. This means that `Layered` consisting of two `Layer`s and no `Subscriber` will now implement `Debug` if the `Layer`s are `Debug`, regardless of the subscriber type. When the `Layered` is a `Layer` and a `Subscriber`, the behavior will be the same, because the separate `PhantomData` subscriber type param is always the same as the type of the inner subscriber. Because printing the whole type name of the subscriber is potentially verbose (e.g. when the subscriber itself is a big pile of layers), we only include it in alt-mode.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

@jsgf

# 0.2.21 (September 12, 2021) This release introduces the [`Filter`] trait, a new API for [per-layer filtering][plf]. This allows controlling which spans and events are recorded by various layers individually, rather than globally. In addition, it adds a new [`Targets`] filter, which provides a lighter-weight version of the filtering provided by [`EnvFilter`], as well as other smaller API improvements and fixes. ### Deprecated - **registry**: `SpanRef::parent_id`, which cannot properly support per-layer filtering. Use `.parent().map(SpanRef::id)` instead. ([#1523]) ### Fixed - **layer** `Context` methods that are provided when the `Subscriber` implements `LookupSpan` no longer require the "registry" feature flag ([#1525]) - **layer** `fmt::Debug` implementation for `Layered` no longer requires the `S` type parameter to implement `Debug` ([#1528]) ### Added - **registry**: `Filter` trait, `Filtered` type, `Layer::with_filter` method, and other APIs for per-layer filtering ([#1523]) - **filter**: `FilterFn` and `DynFilterFn` types that implement global (`Layer`) and per-layer (`Filter`) filtering for closures and function pointers ([#1523]) - **filter**: `Targets` filter, which implements a lighter-weight form of `EnvFilter`-like filtering ([#1550]) - **env-filter**: Added support for filtering on floating-point values ([#1507]) - **layer**: `Layer::on_layer` callback, called when layering the `Layer` onto a `Subscriber` ([#1523]) - **layer**: `Layer` implementations for `Box<L>` and `Arc<L>` where `L: Layer` ([#1536]) - **layer**: `Layer` implementations for `Box<dyn Layer<S> + Send + Sync + 'static>` and `Arc<dyn Layer<S> + Send + Sync + 'static>` ([#1536]) - A number of small documentation fixes and improvements ([#1553], [#1544], [#1539], [#1524]) Special thanks to new contributors @jsgf and @maxburke for contributing to this release! [`Filter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/trait.Filter.html [`plf`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/index.html#per-layer-filtering [`Targets`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.Targets.html [`EnvFilter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.EnvFilter.html [#1507]: #1507 [#1523]: #1523 [#1524]: #1524 [#1525]: #1525 [#1528]: #1528 [#1539]: #1539 [#1544]: #1544 [#1550]: #1550 [#1553]: #1553

@jsgf

# 0.2.21 (September 12, 2021) This release introduces the [`Filter`] trait, a new API for [per-layer filtering][plf]. This allows controlling which spans and events are recorded by various layers individually, rather than globally. In addition, it adds a new [`Targets`] filter, which provides a lighter-weight version of the filtering provided by [`EnvFilter`], as well as other smaller API improvements and fixes. ### Deprecated - **registry**: `SpanRef::parent_id`, which cannot properly support per-layer filtering. Use `.parent().map(SpanRef::id)` instead. ([#1523]) ### Fixed - **layer** `Context` methods that are provided when the `Subscriber` implements `LookupSpan` no longer require the "registry" feature flag ([#1525]) - **layer** `fmt::Debug` implementation for `Layered` no longer requires the `S` type parameter to implement `Debug` ([#1528]) ### Added - **registry**: `Filter` trait, `Filtered` type, `Layer::with_filter` method, and other APIs for per-layer filtering ([#1523]) - **filter**: `FilterFn` and `DynFilterFn` types that implement global (`Layer`) and per-layer (`Filter`) filtering for closures and function pointers ([#1523]) - **filter**: `Targets` filter, which implements a lighter-weight form of `EnvFilter`-like filtering ([#1550]) - **env-filter**: Added support for filtering on floating-point values ([#1507]) - **layer**: `Layer::on_layer` callback, called when layering the `Layer` onto a `Subscriber` ([#1523]) - **layer**: `Layer` implementations for `Box<L>` and `Arc<L>` where `L: Layer` ([#1536]) - **layer**: `Layer` implementations for `Box<dyn Layer<S> + Send + Sync + 'static>` and `Arc<dyn Layer<S> + Send + Sync + 'static>` ([#1536]) - A number of small documentation fixes and improvements ([#1553], [#1544], [#1539], [#1524]) Special thanks to new contributors @jsgf and @maxburke for contributing to this release! [`Filter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/trait.Filter.html [`plf`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/index.html#per-layer-filtering [`Targets`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.Targets.html [`EnvFilter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.EnvFilter.html [#1507]: #1507 [#1523]: #1523 [#1524]: #1524 [#1525]: #1525 [#1528]: #1528 [#1539]: #1539 [#1544]: #1544 [#1550]: #1550 [#1553]: #1553

@jsgf

# 0.2.21 (September 12, 2021) This release introduces the [`Filter`] trait, a new API for [per-layer filtering][plf]. This allows controlling which spans and events are recorded by various layers individually, rather than globally. In addition, it adds a new [`Targets`] filter, which provides a lighter-weight version of the filtering provided by [`EnvFilter`], as well as other smaller API improvements and fixes. ### Deprecated - **registry**: `SpanRef::parent_id`, which cannot properly support per-layer filtering. Use `.parent().map(SpanRef::id)` instead. ([#1523]) ### Fixed - **layer** `Context` methods that are provided when the `Subscriber` implements `LookupSpan` no longer require the "registry" feature flag ([#1525]) - **layer** `fmt::Debug` implementation for `Layered` no longer requires the `S` type parameter to implement `Debug` ([#1528]) ### Added - **registry**: `Filter` trait, `Filtered` type, `Layer::with_filter` method, and other APIs for per-layer filtering ([#1523]) - **filter**: `FilterFn` and `DynFilterFn` types that implement global (`Layer`) and per-layer (`Filter`) filtering for closures and function pointers ([#1523]) - **filter**: `Targets` filter, which implements a lighter-weight form of `EnvFilter`-like filtering ([#1550]) - **env-filter**: Added support for filtering on floating-point values ([#1507]) - **layer**: `Layer::on_layer` callback, called when layering the `Layer` onto a `Subscriber` ([#1523]) - **layer**: `Layer` implementations for `Box<L>` and `Arc<L>` where `L: Layer` ([#1536]) - **layer**: `Layer` implementations for `Box<dyn Layer>` and `Arc<dyn Layer>` ([#1536]) - A number of small documentation fixes and improvements ([#1553], [#1544], [#1539], [#1524]) Special thanks to new contributors @jsgf and @maxburke for contributing to this release! [`Filter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/trait.Filter.html [plf]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/index.html#per-layer-filtering [`Targets`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.Targets.html [`EnvFilter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.EnvFilter.html [#1507]: #1507 [#1523]: #1523 [#1524]: #1524 [#1525]: #1525 [#1528]: #1528 [#1539]: #1539 [#1544]: #1544 [#1550]: #1550 [#1553]: #1553

@jsgf

# 0.2.21 (September 12, 2021) This release introduces the [`Filter`] trait, a new API for [per-layer filtering][plf]. This allows controlling which spans and events are recorded by various layers individually, rather than globally. In addition, it adds a new [`Targets`] filter, which provides a lighter-weight version of the filtering provided by [`EnvFilter`], as well as other smaller API improvements and fixes. ### Deprecated - **registry**: `SpanRef::parent_id`, which cannot properly support per-layer filtering. Use `.parent().map(SpanRef::id)` instead. ([#1523]) ### Fixed - **layer** `Context` methods that are provided when the `Subscriber` implements `LookupSpan` no longer require the "registry" feature flag ([#1525]) - **layer** `fmt::Debug` implementation for `Layered` no longer requires the `S` type parameter to implement `Debug` ([#1528]) ### Added - **registry**: `Filter` trait, `Filtered` type, `Layer::with_filter` method, and other APIs for per-layer filtering ([#1523]) - **filter**: `FilterFn` and `DynFilterFn` types that implement global (`Layer`) and per-layer (`Filter`) filtering for closures and function pointers ([#1523]) - **filter**: `Targets` filter, which implements a lighter-weight form of `EnvFilter`-like filtering ([#1550]) - **env-filter**: Added support for filtering on floating-point values ([#1507]) - **layer**: `Layer::on_layer` callback, called when layering the `Layer` onto a `Subscriber` ([#1523]) - **layer**: `Layer` implementations for `Box<L>` and `Arc<L>` where `L: Layer` ([#1536]) - **layer**: `Layer` implementations for `Box<dyn Layer>` and `Arc<dyn Layer>` ([#1536]) - A number of small documentation fixes and improvements ([#1553], [#1544], [#1539], [#1524]) Special thanks to new contributors @jsgf and @maxburke for contributing to this release! [`Filter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/trait.Filter.html [plf]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/index.html#per-layer-filtering [`Targets`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.Targets.html [`EnvFilter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.EnvFilter.html [#1507]: #1507 [#1523]: #1523 [#1524]: #1524 [#1525]: #1525 [#1528]: #1528 [#1539]: #1539 [#1544]: #1544 [#1550]: #1550 [#1553]: #1553

Currently, `Layered` only implements `fmt::Debug` if the outer layer, the inner layer, *and* the subscriber type parameters all implement `fmt::Debug`. However, in the case of a `Layered` with two `Layer`s, the subscriber itself is not present --- it's only a `PhantomData`. So the `fmt::Debug` implementation should be possible when only the actual `layer` and `inner` values are `Debug`. For the `PhantomData`, we can just print the type name. This means that `Layered` consisting of two `Layer`s and no `Subscriber` will now implement `Debug` if the `Layer`s are `Debug`, regardless of the subscriber type. When the `Layered` is a `Layer` and a `Subscriber`, the behavior will be the same, because the separate `PhantomData` subscriber type param is always the same as the type of the inner subscriber. Because printing the whole type name of the subscriber is potentially verbose (e.g. when the subscriber itself is a big pile of layers), we only include it in alt-mode.

@jsgf

# 0.2.21 (September 12, 2021) This release introduces the [`Filter`] trait, a new API for [per-layer filtering][plf]. This allows controlling which spans and events are recorded by various layers individually, rather than globally. In addition, it adds a new [`Targets`] filter, which provides a lighter-weight version of the filtering provided by [`EnvFilter`], as well as other smaller API improvements and fixes. ### Deprecated - **registry**: `SpanRef::parent_id`, which cannot properly support per-layer filtering. Use `.parent().map(SpanRef::id)` instead. ([tokio-rs#1523]) ### Fixed - **layer** `Context` methods that are provided when the `Subscriber` implements `LookupSpan` no longer require the "registry" feature flag ([tokio-rs#1525]) - **layer** `fmt::Debug` implementation for `Layered` no longer requires the `S` type parameter to implement `Debug` ([tokio-rs#1528]) ### Added - **registry**: `Filter` trait, `Filtered` type, `Layer::with_filter` method, and other APIs for per-layer filtering ([tokio-rs#1523]) - **filter**: `FilterFn` and `DynFilterFn` types that implement global (`Layer`) and per-layer (`Filter`) filtering for closures and function pointers ([tokio-rs#1523]) - **filter**: `Targets` filter, which implements a lighter-weight form of `EnvFilter`-like filtering ([tokio-rs#1550]) - **env-filter**: Added support for filtering on floating-point values ([tokio-rs#1507]) - **layer**: `Layer::on_layer` callback, called when layering the `Layer` onto a `Subscriber` ([tokio-rs#1523]) - **layer**: `Layer` implementations for `Box<L>` and `Arc<L>` where `L: Layer` ([tokio-rs#1536]) - **layer**: `Layer` implementations for `Box<dyn Layer>` and `Arc<dyn Layer>` ([tokio-rs#1536]) - A number of small documentation fixes and improvements ([tokio-rs#1553], [tokio-rs#1544], [tokio-rs#1539], [tokio-rs#1524]) Special thanks to new contributors @jsgf and @maxburke for contributing to this release! [`Filter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/trait.Filter.html [plf]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/layer/index.html#per-layer-filtering [`Targets`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.Targets.html [`EnvFilter`]: https://docs.rs/tracing-subscriber/0.2.21/tracing_subscriber/filter/struct.EnvFilter.html [tokio-rs#1507]: tokio-rs#1507 [tokio-rs#1523]: tokio-rs#1523 [tokio-rs#1524]: tokio-rs#1524 [tokio-rs#1525]: tokio-rs#1525 [tokio-rs#1528]: tokio-rs#1528 [tokio-rs#1539]: tokio-rs#1539 [tokio-rs#1544]: tokio-rs#1544 [tokio-rs#1550]: tokio-rs#1550 [tokio-rs#1553]: tokio-rs#1553

hawkw requested a review from davidbarsky August 30, 2021 17:31

hawkw self-assigned this Aug 30, 2021

hawkw requested a review from a team as a code owner August 30, 2021 17:31

davidbarsky approved these changes Aug 30, 2021

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hawkw merged commit 06ecec4 into v0.1.x Aug 30, 2021

hawkw deleted the eliza/nicer-debug-layered branch August 30, 2021 17:33

hawkw added a commit that referenced this pull request Aug 30, 2021

add extra fields to Debug impl from #1528

7d015e1

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

hawkw added a commit that referenced this pull request Sep 2, 2021

add extra fields to Debug impl from #1528

f68d5a3

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

hawkw added a commit that referenced this pull request Sep 4, 2021

add extra fields to Debug impl from #1528

96ff3a9

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

davidbarsky mentioned this pull request Sep 26, 2023

chore: backport roughly a year's worth of changes #2728

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subscriber: nicer `fmt::Debug` for `Layered` #1528

subscriber: nicer `fmt::Debug` for `Layered` #1528

hawkw commented Aug 30, 2021

subscriber: nicer fmt::Debug for Layered #1528

subscriber: nicer fmt::Debug for Layered #1528

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hawkw commented Aug 30, 2021

subscriber: nicer `fmt::Debug` for `Layered` #1528

subscriber: nicer `fmt::Debug` for `Layered` #1528