chore: remove *all* extern crate statements (tokio-rs#1738)

Depends on tokio-rs#1737

This branch removes all remaining `extern crate` statements. Most of
these are in old code and were not removed when updating to Rust 2018.
Whoops!

Our MSRV no longer requires `extern crate`, so we don't need these. The
exception is `extern crate` statements for `std` and `alloc`, which are
still the way these libraries are included explicitly when building for
`no_std` platforms.

In some cases, the tests had to explicitly import the `span!` and
`event!` macros at every use, because their names conflict with the
`span` and `event` modules in the test support code. Oh well.

Signed-off-by: Eliza Weisman <[email protected]>

Author: hawkw

tracing-core/src/subscriber.rs

@@ -246,8 +246,7 @@ pub trait Subscriber: 'static {
     /// but values for them won't be recorded at this time.
     ///
     /// ```rust,ignore
-    /// #[macro_use]
-    /// extern crate tracing;
+    /// # use tracing::span;
     ///
     /// let mut span = span!("my_span", foo = 3, bar, baz);
     ///

tracing/benches/subscriber.rs

@@ -0,0 +1,189 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use tracing::Level;
+
+use std::{
+    fmt,
+    sync::{Mutex, MutexGuard},
+};
+use tracing::{field, span, Event, Id, Metadata};
+
+/// A subscriber that is enabled but otherwise does nothing.
+struct EnabledSubscriber;
+
+impl tracing::Subscriber for EnabledSubscriber {
+    fn new_span(&self, span: &span::Attributes<'_>) -> Id {
+        let _ = span;
+        Id::from_u64(0xDEAD_FACE)
+    }
+
+    fn event(&self, event: &Event<'_>) {
+        let _ = event;
+    }
+
+    fn record(&self, span: &Id, values: &span::Record<'_>) {
+        let _ = (span, values);
+    }
+
+    fn record_follows_from(&self, span: &Id, follows: &Id) {
+        let _ = (span, follows);
+    }
+
+    fn enabled(&self, metadata: &Metadata<'_>) -> bool {
+        let _ = metadata;
+        true
+    }
+
+    fn enter(&self, span: &Id) {
+        let _ = span;
+    }
+
+    fn exit(&self, span: &Id) {
+        let _ = span;
+    }
+}
+
+/// Simulates a subscriber that records span data.
+struct VisitingSubscriber(Mutex<String>);
+
+struct Visitor<'a>(MutexGuard<'a, String>);
+
+impl<'a> field::Visit for Visitor<'a> {
+    fn record_debug(&mut self, _field: &field::Field, value: &dyn fmt::Debug) {
+        use std::fmt::Write;
+        let _ = write!(&mut *self.0, "{:?}", value);
+    }
+}
+
+impl tracing::Subscriber for VisitingSubscriber {
+    fn new_span(&self, span: &span::Attributes<'_>) -> Id {
+        let mut visitor = Visitor(self.0.lock().unwrap());
+        span.record(&mut visitor);
+        Id::from_u64(0xDEAD_FACE)
+    }
+
+    fn record(&self, _span: &Id, values: &span::Record<'_>) {
+        let mut visitor = Visitor(self.0.lock().unwrap());
+        values.record(&mut visitor);
+    }
+
+    fn event(&self, event: &Event<'_>) {
+        let mut visitor = Visitor(self.0.lock().unwrap());
+        event.record(&mut visitor);
+    }
+
+    fn record_follows_from(&self, span: &Id, follows: &Id) {
+        let _ = (span, follows);
+    }
+
+    fn enabled(&self, metadata: &Metadata<'_>) -> bool {
+        let _ = metadata;
+        true
+    }
+
+    fn enter(&self, span: &Id) {
+        let _ = span;
+    }
+
+    fn exit(&self, span: &Id) {
+        let _ = span;
+    }
+}
+
+const N_SPANS: usize = 100;
+
+fn criterion_benchmark(c: &mut Criterion) {
+    c.bench_function("span_no_fields", |b| {
+        tracing::subscriber::with_default(EnabledSubscriber, || {
+            b.iter(|| span!(Level::TRACE, "span"))
+        });
+    });
+
+    c.bench_function("enter_span", |b| {
+        tracing::subscriber::with_default(EnabledSubscriber, || {
+            let span = span!(Level::TRACE, "span");
+            #[allow(clippy::unit_arg)]
+            b.iter(|| black_box(span.in_scope(|| {})))
+        });
+    });
+
+    c.bench_function("span_repeatedly", |b| {
+        #[inline]
+        fn mk_span(i: u64) -> tracing::Span {
+            span!(Level::TRACE, "span", i = i)
+        }
+
+        let n = black_box(N_SPANS);
+        tracing::subscriber::with_default(EnabledSubscriber, || {
+            b.iter(|| (0..n).fold(mk_span(0), |_, i| mk_span(i as u64)))
+        });
+    });
+
+    c.bench_function("span_with_fields", |b| {
+        tracing::subscriber::with_default(EnabledSubscriber, || {
+            b.iter(|| {
+                span!(
+                    Level::TRACE,
+                    "span",
+                    foo = "foo",
+                    bar = "bar",
+                    baz = 3,
+                    quuux = tracing::field::debug(0.99)
+                )
+            })
+        });
+    });
+
+    c.bench_function("span_with_fields_record", |b| {
+        let subscriber = VisitingSubscriber(Mutex::new(String::from("")));
+        tracing::subscriber::with_default(subscriber, || {
+            b.iter(|| {
+                span!(
+                    Level::TRACE,
+                    "span",
+                    foo = "foo",
+                    bar = "bar",
+                    baz = 3,
+                    quuux = tracing::field::debug(0.99)
+                )
+            })
+        });
+    });
+}
+
+fn bench_dispatch(c: &mut Criterion) {
+    let mut group = c.benchmark_group("dispatch");
+    group.bench_function("no_dispatch_get_ref", |b| {
+        b.iter(|| {
+            tracing::dispatcher::get_default(|current| {
+                black_box(&current);
+            })
+        })
+    });
+    group.bench_function("no_dispatch_get_clone", |b| {
+        b.iter(|| {
+            let current = tracing::dispatcher::get_default(|current| current.clone());
+            black_box(current);
+        })
+    });
+    group.bench_function("get_ref", |b| {
+        tracing::subscriber::with_default(EnabledSubscriber, || {
+            b.iter(|| {
+                tracing::dispatcher::get_default(|current| {
+                    black_box(&current);
+                })
+            })
+        })
+    });
+    group.bench_function("get_clone", |b| {
+        tracing::subscriber::with_default(EnabledSubscriber, || {
+            b.iter(|| {
+                let current = tracing::dispatcher::get_default(|current| current.clone());
+                black_box(current);
+            })
+        })
+    });
+    group.finish();
+}
+
+criterion_group!(benches, criterion_benchmark, bench_dispatch);
+criterion_main!(benches);

tracing/tests/span.rs

@@ -348,8 +348,8 @@ fn entered() {
         .done()
         .run_with_handle();
     with_default(subscriber, || {
-        let _span = span!(Level::TRACE, "foo").entered();
-        debug!("dropping guard...");
+        let _span = tracing::span!(Level::TRACE, "foo").entered();
+        tracing::debug!("dropping guard...");
     });
 
     handle.assert_finished();
@@ -366,9 +366,9 @@ fn entered_api() {
         .done()
         .run_with_handle();
     with_default(subscriber, || {
-        let span = span!(Level::TRACE, "foo").entered();
+        let span = tracing::span!(Level::TRACE, "foo").entered();
         let _derefs_to_span = span.id();
-        debug!("exiting span...");
+        tracing::debug!("exiting span...");
         let _: Span = span.exit();
     });
 

tracing/tests/subscriber.rs

@@ -5,9 +5,6 @@
 // The alternative would be for each of these tests to be defined in a separate
 // file, which is :(
 #![cfg(feature = "std")]
-
-#[macro_use]
-extern crate tracing;
 use tracing::{
     field::display,
     span::{Attributes, Id, Record},
@@ -34,7 +31,7 @@ fn event_macros_dont_infinite_loop() {
 
         fn enabled(&self, meta: &Metadata<'_>) -> bool {
             assert!(meta.fields().iter().any(|f| f.name() == "foo"));
-            event!(Level::TRACE, bar = false);
+            tracing::event!(Level::TRACE, bar = false);
             true
         }
 
@@ -48,7 +45,7 @@ fn event_macros_dont_infinite_loop() {
 
         fn event(&self, event: &Event<'_>) {
             assert!(event.metadata().fields().iter().any(|f| f.name() == "foo"));
-            event!(Level::TRACE, baz = false);
+            tracing::event!(Level::TRACE, baz = false);
         }
 
         fn enter(&self, _: &Id) {}
@@ -57,7 +54,7 @@ fn event_macros_dont_infinite_loop() {
     }
 
     with_default(TestSubscriber, || {
-        event!(Level::TRACE, foo = false);
+        tracing::event!(Level::TRACE, foo = false);
     })
 }
 
@@ -81,7 +78,7 @@ fn boxed_subscriber() {
 
     with_default(subscriber, || {
         let from = "my span";
-        let span = span!(
+        let span = tracing::span!(
             Level::TRACE,
             "foo",
             bar = format_args!("hello from {}", from)
@@ -119,7 +116,7 @@ fn arced_subscriber() {
     // Test using a clone of the `Arc`ed subscriber
     with_default(subscriber.clone(), || {
         let from = "my span";
-        let span = span!(
+        let span = tracing::span!(
             Level::TRACE,
             "foo",
             bar = format_args!("hello from {}", from)