default all feature flags to off (#1811)

Changes the set of `default` feature flags to `[]`. By default, only
core traits are included without specifying feature flags. This makes it
easier for users to pick the components they need.

For convenience, a `full` feature flag is included that includes all
components.

Tests are configured to require the `full` feature. Testing individual
feature flags will need to be moved to a separate crate.

Closes #1791

1 files changed, 5 insertions, 3 deletions

diff --git a/tokio/src/sync/mod.rs b/tokio/src/sync/mod.rs
index 2954eb85..0db703bb 100644
--- a/tokio/src/sync/mod.rs
+++ b/tokio/src/sync/mod.rs
@@ -40,9 +40,11 @@ cfg_not_sync! {
         pub(crate) use task::AtomicWaker;
     }
 
-    cfg_rt_core! {
-        pub(crate) mod oneshot;
-    }
+    #[cfg(any(
+            feature = "rt-core",
+            feature = "process",
+            feature = "signal"))]
+    pub(crate) mod oneshot;
 
     cfg_signal! {
         pub(crate) mod mpsc;