fix(subscriber): remove unused AggregatorHandle and fix other lints

A number of new or updated Clippy lints in Rust 1.80.0 need to be fixed.

An update to the `dead_code` pointed out that the `AggregatorHandle` is
not used, and it is not constructable from outside the crate because it
has a private field. This struct was introduced in #451 as part of the
`Server::into_parts` method. Originally, this method was going to return
the `AggregatorHandle`, which wrapped the join handle from the task
where the `Aggregator` had been spawned. This was later replaced by
returning the `Aggregator` itself, which the user had the obligation to
spawn themselves. However, it seems that the `AggregatorHandle` wasn't
removed, even though it was never used.

A new lint is the one for unexpected `--cfg` items. We now need to
declare those in `Cargo.toml`.

An update to `needless_borrows_for_generic_args` causes a false positive
changing a `&mut` to a move, which we can't do as the same value is used
afterwards.

console-subscriber/Cargo.toml

@@ -63,6 +63,10 @@ futures = "0.3"
 http = "1.1"
 tower-http = { version = "0.5", features = ["cors"] }
 
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [ 'cfg(tokio_unstable)', 'cfg(console_without_tokio_unstable)' ]
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]

console-subscriber/README.md

@@ -94,12 +94,12 @@ runtime][Tokio] is considered *experimental*. In order to use
   level].
 
   + If you're using the [`console_subscriber::init()`][init] or
-  [`console_subscriber::Builder`][builder] APIs, these targets are enabled
-  automatically.
+    [`console_subscriber::Builder`][builder] APIs, these targets are enabled
+    automatically.
 
   + If you are manually configuring the `tracing` subscriber using the
-  [`EnvFilter`] or [`Targets`] filters from [`tracing-subscriber`], add
-  `"tokio=trace,runtime=trace"` to your filter configuration.
+    [`EnvFilter`] or [`Targets`] filters from [`tracing-subscriber`], add
+    `"tokio=trace,runtime=trace"` to your filter configuration.
 
   + Also, ensure you have not enabled any of the [compile time filter
     features][compile_time_filters] in your `Cargo.toml`.

console-subscriber/src/lib.rs

@@ -1187,38 +1187,6 @@ pub struct ServerParts {
     pub aggregator: Aggregator,
 }
 
-/// Aggregator handle.
-///
-/// This object is returned from [`Server::into_parts`]. It can be
-/// used to abort the aggregator task.
-///
-/// The aggregator collects the traces that implement the async runtime
-/// being observed and prepares them to be served by the gRPC server.
-///
-/// Normally, if the server, started with [`Server::serve`] or
-/// [`Server::serve_with`] stops for any reason, the aggregator is aborted,
-/// hoewver, if the server was started with the [`InstrumentServer`] returned
-/// from [`Server::into_parts`], then it is the responsibility of the user
-/// of the API to stop the aggregator task by calling [`abort`] on this
-/// object.
-///
-/// [`abort`]: fn@crate::AggregatorHandle::abort
-pub struct AggregatorHandle {
-    join_handle: JoinHandle<()>,
-}
-
-impl AggregatorHandle {
-    /// Aborts the task running this aggregator.
-    ///
-    /// To avoid having a disconnected aggregator running forever, this
-    /// method should be called when the [`tonic::transport::Server`] started
-    /// with the [`InstrumentServer`] also returned from [`Server::into_parts`]
-    /// stops running.
-    pub fn abort(&mut self) {
-        self.join_handle.abort();
-    }
-}
-
 #[tonic::async_trait]
 impl proto::instrument::instrument_server::Instrument for Server {
     type WatchUpdatesStream =

console-subscriber/src/record.rs

@@ -83,6 +83,9 @@ fn record_io(file: File, rx: Receiver<Event>) -> io::Result<()> {
     use std::io::{BufWriter, Write};
 
     fn write<T: Serialize>(mut file: &mut BufWriter<File>, val: &T) -> io::Result<()> {
+        // Clippy throws a false positive here. We can't actually pass the owned `file` to
+        // `to_writer` because we need it again in the line blow.
+        #[allow(clippy::needless_borrows_for_generic_args)]
         serde_json::to_writer(&mut file, val)?;
         file.write_all(b"\n")
     }