chore: fix warnings about unexpected cfg(feature) values (#2968)

* futures: Remove executor::futures_preview module

The cfg for it was impossible to enable as of
#441.

* subscriber: Fix cfgs for nu-ansi-term

Previously, enabling this optional dependency did not do anything.

* Unconditionally ignore flaky tests

No need to use a custom cfg to run off-by-default tests.

* tower: Delete unused code

It might be possible to make it work with tower_make instead, but that
crate looks to be unmaintained (no longer present in the tower repo
which is specified as the repository URL) so it should likely just be
removed as a dependency.

tracing-futures/src/executor/mod.rs

@@ -1,11 +1,6 @@
 #[cfg(feature = "futures-01")]
 mod futures_01;
 
-#[cfg(feature = "futures_preview")]
-mod futures_preview;
-#[cfg(feature = "futures_preview")]
-pub use self::futures_preview::*;
-
 #[cfg(feature = "futures-03")]
 mod futures_03;
 #[cfg(feature = "futures-03")]

tracing-subscriber/src/filter/env/builder.rs

@@ -210,15 +210,15 @@ impl Builder {
         }
 
         if !disabled.is_empty() {
-            #[cfg(feature = "nu_ansi_term")]
+            #[cfg(feature = "nu-ansi-term")]
             use nu_ansi_term::{Color, Style};
             // NOTE: We can't use a configured `MakeWriter` because the EnvFilter
             // has no knowledge of any underlying subscriber or collector, which
             // may or may not use a `MakeWriter`.
             let warn = |msg: &str| {
-                #[cfg(not(feature = "nu_ansi_term"))]
+                #[cfg(not(feature = "nu-ansi-term"))]
                 let msg = format!("warning: {}", msg);
-                #[cfg(feature = "nu_ansi_term")]
+                #[cfg(feature = "nu-ansi-term")]
                 let msg = {
                     let bold = Style::new().bold();
                     let mut warning = Color::Yellow.paint("warning");
@@ -228,9 +228,9 @@ impl Builder {
                 eprintln!("{}", msg);
             };
             let ctx_prefixed = |prefix: &str, msg: &str| {
-                #[cfg(not(feature = "nu_ansi_term"))]
+                #[cfg(not(feature = "nu-ansi-term"))]
                 let msg = format!("{} {}", prefix, msg);
-                #[cfg(feature = "nu_ansi_term")]
+                #[cfg(feature = "nu-ansi-term")]
                 let msg = {
                     let mut equal = Color::Fixed(21).paint("="); // dark blue
                     equal.style_ref_mut().is_bold = true;
@@ -241,9 +241,9 @@ impl Builder {
             let ctx_help = |msg| ctx_prefixed("help:", msg);
             let ctx_note = |msg| ctx_prefixed("note:", msg);
             let ctx = |msg: &str| {
-                #[cfg(not(feature = "nu_ansi_term"))]
+                #[cfg(not(feature = "nu-ansi-term"))]
                 let msg = format!("note: {}", msg);
-                #[cfg(feature = "nu_ansi_term")]
+                #[cfg(feature = "nu-ansi-term")]
                 let msg = {
                     let mut pipe = Color::Fixed(21).paint("|");
                     pipe.style_ref_mut().is_bold = true;

tracing-subscriber/tests/field_filter.rs

@@ -5,7 +5,7 @@ use tracing_mock::*;
 use tracing_subscriber::{filter::EnvFilter, prelude::*};
 
 #[test]
-#[cfg_attr(not(flaky_tests), ignore)]
+#[ignore] // flaky, use `cargo test -- --ignored` or `--include-ignored` to run
 fn field_filter_events() {
     let filter: EnvFilter = "[{thing}]=debug".parse().expect("filter should parse");
     let (subscriber, finished) = collector::mock()
@@ -35,7 +35,7 @@ fn field_filter_events() {
 }
 
 #[test]
-#[cfg_attr(not(flaky_tests), ignore)]
+#[ignore] // flaky, use `cargo test -- --ignored` or `--include-ignored` to run
 fn field_filter_spans() {
     let filter: EnvFilter = "[{enabled=true}]=debug"
         .parse()

tracing-tower/src/lib.rs

@@ -71,33 +71,8 @@ where
     }
 }
 
-#[cfg(feature = "tower-util")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tower-util")))]
-pub trait InstrumentMake<T, R>
-where
-    Self: tower_util::MakeService<T, R> + Sized,
-{
-    fn with_traced_service<G>(self, get_span: G) -> service_span::MakeService<Self, T, R, G>
-    where
-        G: GetSpan<T>,
-    {
-        service_span::MakeService::new(self, get_span)
-    }
-
-    fn with_traced_requests<G>(self, get_span: G) -> request_span::MakeService<Self, R, G>
-    where
-        G: GetSpan<R> + Clone,
-    {
-        request_span::MakeService::new(self, get_span)
-    }
-}
-
 impl<S, R> InstrumentableService<R> for S where S: Service<R> + Sized {}
 
-#[cfg(feature = "tower-util")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tower-util")))]
-impl<M, T, R> InstrumentMake<T, R> for M where M: tower_util::MakeService<T, R> {}
-
 pub trait GetSpan<T>: crate::sealed::Sealed<T> {
     fn span_for(&self, target: &T) -> tracing::Span;
 }

tracing-tower/src/service_span.rs

@@ -16,10 +16,6 @@ pub struct Service<S> {
 #[cfg_attr(docsrs, doc(cfg(feature = "tower-layer")))]
 pub use self::layer::*;
 
-#[cfg(feature = "tower-util")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tower-util")))]
-pub use self::make::MakeService;
-
 #[cfg(feature = "tower-layer")]
 #[cfg_attr(docsrs, doc(cfg(feature = "tower-layer")))]
 mod layer {