backport recent commits from master

tracing-attributes/src/attr.rs

@@ -11,6 +11,8 @@ pub(crate) struct InstrumentArgs {
     level: Option<Level>,
     pub(crate) name: Option<LitStr>,
     target: Option<LitStr>,
+    pub(crate) parent: Option<Expr>,
+    pub(crate) follows_from: Option<Expr>,
     pub(crate) skips: HashSet<Ident>,
     pub(crate) skip_all: bool,
     pub(crate) fields: Option<Fields>,
@@ -123,6 +125,18 @@ impl Parse for InstrumentArgs {
                 }
                 let target = input.parse::<StrArg<kw::target>>()?.value;
                 args.target = Some(target);
+            } else if lookahead.peek(kw::parent) {
+                if args.target.is_some() {
+                    return Err(input.error("expected only a single `parent` argument"));
+                }
+                let parent = input.parse::<ExprArg<kw::parent>>()?;
+                args.parent = Some(parent.value);
+            } else if lookahead.peek(kw::follows_from) {
+                if args.target.is_some() {
+                    return Err(input.error("expected only a single `follows_from` argument"));
+                }
+                let follows_from = input.parse::<ExprArg<kw::follows_from>>()?;
+                args.follows_from = Some(follows_from.value);
             } else if lookahead.peek(kw::level) {
                 if args.level.is_some() {
                     return Err(input.error("expected only a single `level` argument"));
@@ -193,6 +207,23 @@ impl<T: Parse> Parse for StrArg<T> {
     }
 }
 
+struct ExprArg<T> {
+    value: Expr,
+    _p: std::marker::PhantomData<T>,
+}
+
+impl<T: Parse> Parse for ExprArg<T> {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let _ = input.parse::<T>()?;
+        let _ = input.parse::<Token![=]>()?;
+        let value = input.parse()?;
+        Ok(Self {
+            value,
+            _p: std::marker::PhantomData,
+        })
+    }
+}
+
 struct Skips(HashSet<Ident>);
 
 impl Parse for Skips {
@@ -374,6 +405,8 @@ mod kw {
     syn::custom_keyword!(skip_all);
     syn::custom_keyword!(level);
     syn::custom_keyword!(target);
+    syn::custom_keyword!(parent);
+    syn::custom_keyword!(follows_from);
     syn::custom_keyword!(name);
     syn::custom_keyword!(err);
     syn::custom_keyword!(ret);

tracing-attributes/src/expand.rs

@@ -88,6 +88,13 @@ fn gen_block<B: ToTokens>(
 
     let level = args.level();
 
+    let follows_from = args.follows_from.iter();
+    let follows_from = quote! {
+        #(for cause in #follows_from {
+            __tracing_attr_span.follows_from(cause);
+        })*
+    };
+
     // generate this inside a closure, so we can return early on errors.
     let span = (|| {
         // Pull out the arguments-to-be-skipped first, so we can filter results
@@ -135,6 +142,8 @@ fn gen_block<B: ToTokens>(
 
         let target = args.target();
 
+        let parent = args.parent.iter();
+
         // filter out skipped fields
         let quoted_fields: Vec<_> = param_names
             .iter()
@@ -182,6 +191,7 @@ fn gen_block<B: ToTokens>(
 
         quote!(tracing::span!(
             target: #target,
+            #(parent: #parent,)*
             #level,
             #span_name,
             #(#quoted_fields,)*
@@ -217,7 +227,7 @@ fn gen_block<B: ToTokens>(
         let mk_fut = match (err_event, ret_event) {
             (Some(err_event), Some(ret_event)) => quote_spanned!(block.span()=>
                 async move {
-                    match async move { #block }.await {
+                    match async move #block.await {
                         #[allow(clippy::unit_arg)]
                         Ok(x) => {
                             #ret_event;
@@ -232,7 +242,7 @@ fn gen_block<B: ToTokens>(
             ),
             (Some(err_event), None) => quote_spanned!(block.span()=>
                 async move {
-                    match async move { #block }.await {
+                    match async move #block.await {
                         #[allow(clippy::unit_arg)]
                         Ok(x) => Ok(x),
                         Err(e) => {
@@ -244,20 +254,21 @@ fn gen_block<B: ToTokens>(
             ),
             (None, Some(ret_event)) => quote_spanned!(block.span()=>
                 async move {
-                    let x = async move { #block }.await;
+                    let x = async move #block.await;
                     #ret_event;
                     x
                 }
             ),
             (None, None) => quote_spanned!(block.span()=>
-                async move { #block }
+                async move #block
             ),
         };
 
         return quote!(
             let __tracing_attr_span = #span;
             let __tracing_instrument_future = #mk_fut;
             if !__tracing_attr_span.is_disabled() {
+                #follows_from
                 tracing::Instrument::instrument(
                     __tracing_instrument_future,
                     __tracing_attr_span
@@ -284,6 +295,7 @@ fn gen_block<B: ToTokens>(
         let __tracing_attr_guard;
         if tracing::level_enabled!(#level) {
             __tracing_attr_span = #span;
+            #follows_from
             __tracing_attr_guard = __tracing_attr_span.enter();
         }
     );

tracing-attributes/src/lib.rs

@@ -345,6 +345,47 @@ mod expand;
 ///     // ...
 /// }
 /// ```
+/// Overriding the generated span's parent:
+/// ```
+/// # use tracing_attributes::instrument;
+/// #[instrument(parent = None)]
+/// pub fn my_function() {
+///     // ...
+/// }
+/// ```
+/// ```
+/// # use tracing_attributes::instrument;
+/// // A struct which owns a span handle.
+/// struct MyStruct
+/// {
+///     span: tracing::Span
+/// }
+///
+/// impl MyStruct
+/// {
+///     // Use the struct's `span` field as the parent span
+///     #[instrument(parent = &self.span, skip(self))]
+///     fn my_method(&self) {}
+/// }
+/// ```
+/// Specifying [`follows_from`] relationships:
+/// ```
+/// # use tracing_attributes::instrument;
+/// #[instrument(follows_from = causes)]
+/// pub fn my_function(causes: &[tracing::Id]) {
+///     // ...
+/// }
+/// ```
+/// Any expression of type `impl IntoIterator<Item = impl Into<Option<Id>>>`
+/// may be provided to `follows_from`; e.g.:
+/// ```
+/// # use tracing_attributes::instrument;
+/// #[instrument(follows_from = [cause])]
+/// pub fn my_function(cause: &tracing::span::EnteredSpan) {
+///     // ...
+/// }
+/// ```
+///
 ///
 /// To skip recording an argument, pass the argument's name to the `skip`:
 ///
@@ -501,6 +542,8 @@ mod expand;
 /// [`INFO`]: https://docs.rs/tracing/latest/tracing/struct.Level.html#associatedconstant.INFO
 /// [empty field]: https://docs.rs/tracing/latest/tracing/field/struct.Empty.html
 /// [field syntax]: https://docs.rs/tracing/latest/tracing/#recording-fields
+/// [`follows_from`]: https://docs.rs/tracing/latest/tracing/struct.Span.html#method.follows_from
+/// [`tracing`]: https://github.com/tokio-rs/tracing
 /// [`fmt::Debug`]: std::fmt::Debug
 #[proc_macro_attribute]
 pub fn instrument(

tracing-attributes/tests/async_fn.rs

@@ -1,5 +1,6 @@
 use tracing_mock::*;
 
+use std::convert::Infallible;
 use std::{future::Future, pin::Pin, sync::Arc};
 use tracing::subscriber::with_default;
 use tracing_attributes::instrument;
@@ -51,6 +52,22 @@ async fn repro_1613_2() {
     // else
 }
 
+// Reproduces https://github.com/tokio-rs/tracing/issues/1831
+#[instrument]
+#[deny(unused_braces)]
+fn repro_1831() -> Pin<Box<dyn Future<Output = ()>>> {
+    Box::pin(async move {})
+}
+
+// This replicates the pattern used to implement async trait methods on nightly using the
+// `type_alias_impl_trait` feature
+#[instrument(ret, err)]
+#[deny(unused_braces)]
+#[allow(clippy::manual_async_fn)]
+fn repro_1831_2() -> impl Future<Output = Result<(), Infallible>> {
+    async { Ok(()) }
+}
+
 #[test]
 fn async_fn_only_enters_for_polls() {
     let (subscriber, handle) = subscriber::mock()

tracing-attributes/tests/follows_from.rs

@@ -0,0 +1,99 @@
+use tracing::{subscriber::with_default, Id, Level, Span};
+use tracing_attributes::instrument;
+use tracing_mock::*;
+
+#[instrument(follows_from = causes, skip(causes))]
+fn with_follows_from_sync(causes: impl IntoIterator<Item = impl Into<Option<Id>>>) {}
+
+#[instrument(follows_from = causes, skip(causes))]
+async fn with_follows_from_async(causes: impl IntoIterator<Item = impl Into<Option<Id>>>) {}
+
+#[instrument(follows_from = [&Span::current()])]
+fn follows_from_current() {}
+
+#[test]
+fn follows_from_sync_test() {
+    let cause_a = span::mock().named("cause_a");
+    let cause_b = span::mock().named("cause_b");
+    let cause_c = span::mock().named("cause_c");
+    let consequence = span::mock().named("with_follows_from_sync");
+
+    let (subscriber, handle) = subscriber::mock()
+        .new_span(cause_a.clone())
+        .new_span(cause_b.clone())
+        .new_span(cause_c.clone())
+        .new_span(consequence.clone())
+        .follows_from(consequence.clone(), cause_a)
+        .follows_from(consequence.clone(), cause_b)
+        .follows_from(consequence.clone(), cause_c)
+        .enter(consequence.clone())
+        .exit(consequence)
+        .done()
+        .run_with_handle();
+
+    with_default(subscriber, || {
+        let cause_a = tracing::span!(Level::TRACE, "cause_a");
+        let cause_b = tracing::span!(Level::TRACE, "cause_b");
+        let cause_c = tracing::span!(Level::TRACE, "cause_c");
+
+        with_follows_from_sync(&[cause_a, cause_b, cause_c])
+    });
+
+    handle.assert_finished();
+}
+
+#[test]
+fn follows_from_async_test() {
+    let cause_a = span::mock().named("cause_a");
+    let cause_b = span::mock().named("cause_b");
+    let cause_c = span::mock().named("cause_c");
+    let consequence = span::mock().named("with_follows_from_async");
+
+    let (subscriber, handle) = subscriber::mock()
+        .new_span(cause_a.clone())
+        .new_span(cause_b.clone())
+        .new_span(cause_c.clone())
+        .new_span(consequence.clone())
+        .follows_from(consequence.clone(), cause_a)
+        .follows_from(consequence.clone(), cause_b)
+        .follows_from(consequence.clone(), cause_c)
+        .enter(consequence.clone())
+        .exit(consequence)
+        .done()
+        .run_with_handle();
+
+    with_default(subscriber, || {
+        block_on_future(async {
+            let cause_a = tracing::span!(Level::TRACE, "cause_a");
+            let cause_b = tracing::span!(Level::TRACE, "cause_b");
+            let cause_c = tracing::span!(Level::TRACE, "cause_c");
+
+            with_follows_from_async(&[cause_a, cause_b, cause_c]).await
+        })
+    });
+
+    handle.assert_finished();
+}
+
+#[test]
+fn follows_from_current_test() {
+    let cause = span::mock().named("cause");
+    let consequence = span::mock().named("follows_from_current");
+
+    let (subscriber, handle) = subscriber::mock()
+        .new_span(cause.clone())
+        .enter(cause.clone())
+        .new_span(consequence.clone())
+        .follows_from(consequence.clone(), cause.clone())
+        .enter(consequence.clone())
+        .exit(consequence)
+        .exit(cause)
+        .done()
+        .run_with_handle();
+
+    with_default(subscriber, || {
+        tracing::span!(Level::TRACE, "cause").in_scope(follows_from_current)
+    });
+
+    handle.assert_finished();
+}