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

Depends on #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 <eliza@buoyant.io>

tracing-core/src/callsite.rs

@@ -12,7 +12,7 @@ use crate::{
     subscriber::Interest,
 };
 
-lazy_static! {
+crate::lazy_static! {
     static ref REGISTRY: Mutex<Registry> = Mutex::new(Registry {
         callsites: Vec::new(),
         dispatchers: Vec::new(),

tracing-core/src/lib.rs

@@ -225,14 +225,11 @@ macro_rules! metadata {
     };
 }
 
-// std uses lazy_static from crates.io
+// when `std` is enabled, use the `lazy_static` crate from crates.io
 #[cfg(feature = "std")]
-#[macro_use]
-extern crate lazy_static;
+pub(crate) use lazy_static::lazy_static;
 
-// no_std uses vendored version of lazy_static 1.4.0 (4216696) with spin
-// This can conflict when included in a project already using std lazy_static
-// Remove this module when cargo enables specifying dependencies for no_std
+// Facade module: `no_std` uses spinlocks, `std` uses the mutexes in the standard library
 #[cfg(not(feature = "std"))]
 #[macro_use]
 mod lazy_static;

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-serde/README.md

@@ -53,10 +53,6 @@ tracing-serde = "0.1"
 Next, add this to your crate:
 
 ```rust
-#[macro_use]
-extern crate tracing;
-extern crate tracing_serde;
-
 use tracing_serde::AsSerde;
 ```
 

tracing/benches/subscriber.rs

@@ -1,6 +1,3 @@
-extern crate criterion;
-extern crate tracing;
-
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 use tracing::Level;
 

tracing/src/level_filters.rs

@@ -65,7 +65,7 @@ pub use tracing_core::{metadata::ParseLevelFilterError, LevelFilter};
 /// [module-level documentation]: ../index.html#compile-time-filters
 pub const STATIC_MAX_LEVEL: LevelFilter = MAX_LEVEL;
 
-cfg_if! {
+cfg_if::cfg_if! {
     if #[cfg(all(not(debug_assertions), feature = "release_max_level_off"))] {
         const MAX_LEVEL: LevelFilter = LevelFilter::OFF;
     } else if #[cfg(all(not(debug_assertions), feature = "release_max_level_error"))] {

tracing/src/lib.rs

@@ -882,9 +882,6 @@
 #[cfg(not(feature = "std"))]
 extern crate alloc;
 
-#[macro_use]
-extern crate cfg_if;
-
 #[cfg(feature = "log")]
 #[doc(hidden)]
 pub use log;

tracing/test-log-support/src/lib.rs

@@ -1,4 +1,3 @@
-extern crate log;
 use log::{LevelFilter, Log, Metadata, Record};
 use std::sync::{Arc, Mutex};
 

tracing/test-log-support/tests/log_no_trace.rs

@@ -1,9 +1,5 @@
-#[macro_use]
-extern crate tracing;
-extern crate test_log_support;
-
 use test_log_support::Test;
-use tracing::Level;
+use tracing::{error, info, span, trace, warn, Level};
 
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
 #[test]

tracing/test-log-support/tests/log_with_trace.rs

@@ -1,9 +1,5 @@
-#[macro_use]
-extern crate tracing;
-extern crate test_log_support;
-
 use test_log_support::Test;
-use tracing::Level;
+use tracing::{error, info, span, trace, warn, Level};
 
 pub struct NopSubscriber;
 

tracing/test-log-support/tests/span_activity_filtered_separately.rs

@@ -1,9 +1,5 @@
-#[macro_use]
-extern crate tracing;
-extern crate test_log_support;
-
 use test_log_support::Test;
-use tracing::Level;
+use tracing::{error, info, span, trace, warn, Level};
 
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
 #[test]

tracing/test-log-support/tests/span_lifecycle_can_be_enabled.rs

@@ -1,9 +1,5 @@
-#[macro_use]
-extern crate tracing;
-extern crate test_log_support;
-
 use test_log_support::Test;
-use tracing::Level;
+use tracing::{error, info, span, trace, warn, Level};
 
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
 #[test]

tracing/test-log-support/tests/span_lifecycle_defaults_off.rs

@@ -1,9 +1,5 @@
-#[macro_use]
-extern crate tracing;
-extern crate test_log_support;
-
 use test_log_support::Test;
-use tracing::Level;
+use tracing::{error, info, span, trace, warn, Level};
 
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
 #[test]

tracing/test-log-support/tests/span_lifecycle_is_trace.rs

@@ -1,9 +1,5 @@
-#[macro_use]
-extern crate tracing;
-extern crate test_log_support;
-
 use test_log_support::Test;
-use tracing::Level;
+use tracing::{error, info, span, trace, warn, Level};
 
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
 #[test]

tracing/test_static_max_level_features/tests/test.rs

@@ -1,9 +1,6 @@
-#[macro_use]
-extern crate tracing;
-
 use std::sync::{Arc, Mutex};
 use tracing::span::{Attributes, Record};
-use tracing::{span, Event, Id, Level, Metadata, Subscriber};
+use tracing::{debug, error, info, span, trace, warn, Collect, Event, Id, Level, Metadata};
 
 struct State {
     last_level: Mutex<Option<Level>>,

tracing/tests/event.rs

@@ -5,17 +5,16 @@
 // 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;
 mod support;
 
 use self::support::*;
 
 use tracing::{
+    debug, error,
     field::{debug, display},
+    info,
     subscriber::with_default,
-    Level,
+    trace, warn, Level,
 };
 
 macro_rules! event_without_message {
@@ -150,7 +149,7 @@ fn one_with_everything() {
         .run_with_handle();
 
     with_default(subscriber, || {
-        event!(
+        tracing::event!(
             target: "whatever",
             Level::ERROR,
             { foo = 666, bar = false, like_a_butterfly = 42.0 },
@@ -176,7 +175,7 @@ fn moved_field() {
         .run_with_handle();
     with_default(subscriber, || {
         let from = "my event";
-        event!(Level::INFO, foo = display(format!("hello from {}", from)))
+        tracing::event!(Level::INFO, foo = display(format!("hello from {}", from)))
     });
 
     handle.assert_finished();
@@ -197,7 +196,7 @@ fn dotted_field_name() {
         .done()
         .run_with_handle();
     with_default(subscriber, || {
-        event!(Level::INFO, foo.bar = true, foo.baz = false);
+        tracing::event!(Level::INFO, foo.bar = true, foo.baz = false);
     });
 
     handle.assert_finished();
@@ -219,7 +218,7 @@ fn borrowed_field() {
     with_default(subscriber, || {
         let from = "my event";
         let mut message = format!("hello from {}", from);
-        event!(Level::INFO, foo = display(&message));
+        tracing::event!(Level::INFO, foo = display(&message));
         message.push_str(", which happened!");
     });
 
@@ -281,7 +280,7 @@ fn display_shorthand() {
         .done()
         .run_with_handle();
     with_default(subscriber, || {
-        event!(Level::TRACE, my_field = %"hello world");
+        tracing::event!(Level::TRACE, my_field = %"hello world");
     });
 
     handle.assert_finished();
@@ -301,7 +300,7 @@ fn debug_shorthand() {
         .done()
         .run_with_handle();
     with_default(subscriber, || {
-        event!(Level::TRACE, my_field = ?"hello world");
+        tracing::event!(Level::TRACE, my_field = ?"hello world");
     });
 
     handle.assert_finished();
@@ -322,7 +321,7 @@ fn both_shorthands() {
         .done()
         .run_with_handle();
     with_default(subscriber, || {
-        event!(Level::TRACE, display_field = %"hello world", debug_field = ?"hello world");
+        tracing::event!(Level::TRACE, display_field = %"hello world", debug_field = ?"hello world");
     });
 
     handle.assert_finished();
@@ -338,8 +337,8 @@ fn explicit_child() {
         .run_with_handle();
 
     with_default(subscriber, || {
-        let foo = span!(Level::TRACE, "foo");
-        event!(parent: foo.id(), Level::TRACE, "bar");
+        let foo = tracing::span!(Level::TRACE, "foo");
+        tracing::event!(parent: foo.id(), Level::TRACE, "bar");
     });
 
     handle.assert_finished();
@@ -359,7 +358,7 @@ fn explicit_child_at_levels() {
         .run_with_handle();
 
     with_default(subscriber, || {
-        let foo = span!(Level::TRACE, "foo");
+        let foo = tracing::span!(Level::TRACE, "foo");
         trace!(parent: foo.id(), "a");
         debug!(parent: foo.id(), "b");
         info!(parent: foo.id(), "c");

tracing/tests/filter_caching_is_lexically_scoped.rs

@@ -7,12 +7,10 @@
 #[cfg(not(feature = "std"))]
 extern crate std;
 
-#[macro_use]
-extern crate tracing;
 mod support;
 
 use self::support::*;
-use tracing::Level;
+use tracing::{span, Level};
 
 use std::sync::{
     atomic::{AtomicUsize, Ordering},

tracing/tests/filters_are_not_reevaluated_for_the_same_span.rs

@@ -5,13 +5,10 @@
 // threads with shared global state lets them interfere with each other
 #[cfg(not(feature = "std"))]
 extern crate std;
-
-#[macro_use]
-extern crate tracing;
 mod support;
 
 use self::support::*;
-use tracing::Level;
+use tracing::{span, Level};
 
 use std::sync::{
     atomic::{AtomicUsize, Ordering},

tracing/tests/filters_are_reevaluated_for_different_call_sites.rs

@@ -6,12 +6,10 @@
 #[cfg(not(feature = "std"))]
 extern crate std;
 
-#[macro_use]
-extern crate tracing;
+use tracing::{span, Level};
 mod support;
 
 use self::support::*;
-use tracing::Level;
 
 use std::sync::{
     atomic::{AtomicUsize, Ordering},

tracing/tests/macros.rs

@@ -1,8 +1,9 @@
 #![deny(warnings)]
-use tracing::Level;
+use tracing::{
+    callsite, debug, debug_span, error, error_span, event, info, info_span, span, trace,
+    trace_span, warn, warn_span, Level,
+};
 
-#[macro_use]
-extern crate tracing;
 // Tests that macros work across various invocation syntax.
 //
 // These are quite repetitive, and _could_ be generated by a macro. However,