macros: append generated test attribute so others are aware of it

tests-build/tests/fail/macros_invalid_input.rs

@@ -45,4 +45,24 @@ async fn test_crate_not_path_invalid() {}
 #[test]
 async fn test_has_second_test_attr() {}
 
+#[tokio::test]
+#[::core::prelude::v1::test]
+async fn test_has_second_test_attr_v1() {}
+
+#[tokio::test]
+#[core::prelude::rust_2015::test]
+async fn test_has_second_test_attr_rust_2015() {}
+
+#[tokio::test]
+#[::std::prelude::rust_2018::test]
+async fn test_has_second_test_attr_rust_2018() {}
+
+#[tokio::test]
+#[std::prelude::rust_2021::test]
+async fn test_has_second_test_attr_rust_2021() {}
+
+#[tokio::test]
+#[tokio::test]
+async fn test_has_generated_second_test_attr() {}
+
 fn main() {}

tests-build/tests/fail/macros_invalid_input.stderr

@@ -76,20 +76,40 @@ error: Failed to parse value of `crate` as path: "456"
 41 | #[tokio::test(crate = "456")]
    |                       ^^^^^
 
-error: second test attribute is supplied
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
   --> $DIR/macros_invalid_input.rs:45:1
    |
 45 | #[test]
    | ^^^^^^^
 
-error: duplicated attribute
-  --> $DIR/macros_invalid_input.rs:45:1
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:49:1
    |
-45 | #[test]
-   | ^^^^^^^
+49 | #[::core::prelude::v1::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:53:1
+   |
+53 | #[core::prelude::rust_2015::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:57:1
+   |
+57 | #[::std::prelude::rust_2018::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:61:1
+   |
+61 | #[std::prelude::rust_2021::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:64:1
    |
-note: the lint level is defined here
-  --> $DIR/macros_invalid_input.rs:1:9
+64 | #[tokio::test]
+   | ^^^^^^^^^^^^^^
    |
-1  | #![deny(duplicate_macro_attributes)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the attribute macro `tokio::test` (in Nightly builds, run with -Z macro-backtrace for more info)

tokio-macros/src/entry.rs

@@ -360,7 +360,7 @@ fn parse_knobs(mut input: ItemFn, is_test: bool, config: FinalConfig) -> TokenSt
         rt = quote_spanned! {last_stmt_start_span=> #rt.start_paused(#v) };
     }
 
-    let header = if is_test {
+    let generated_attrs = if is_test {
         quote! {
             #[::core::prelude::v1::test]
         }
@@ -410,7 +410,7 @@ fn parse_knobs(mut input: ItemFn, is_test: bool, config: FinalConfig) -> TokenSt
         }
     };
 
-    input.into_tokens(header, body, last_block)
+    input.into_tokens(generated_attrs, body, last_block)
 }
 
 fn token_stream_with_error(mut tokens: TokenStream, error: syn::Error) -> TokenStream {
@@ -442,6 +442,35 @@ pub(crate) fn main(args: TokenStream, item: TokenStream, rt_multi_thread: bool)
     }
 }
 
+// Check whether given attribute is a test attribute of forms:
+// * `#[test]`
+// * `#[core::prelude::*::test]` or `#[::core::prelude::*::test]`
+// * `#[std::prelude::*::test]` or `#[::std::prelude::*::test]`
+fn is_test_attribute(attr: &Attribute) -> bool {
+    let path = match &attr.meta {
+        syn::Meta::Path(path) => path,
+        _ => return false,
+    };
+    let candidates = [
+        ["core", "prelude", "*", "test"],
+        ["std", "prelude", "*", "test"],
+    ];
+    if path.leading_colon.is_none()
+        && path.segments.len() == 1
+        && path.segments[0].arguments.is_none()
+        && path.segments[0].ident == "test"
+    {
+        return true;
+    } else if path.segments.len() != candidates[0].len() {
+        return false;
+    }
+    candidates.into_iter().any(|segments| {
+        path.segments.iter().zip(segments).all(|(segment, path)| {
+            segment.arguments.is_none() && (path == "*" || segment.ident == path)
+        })
+    })
+}
+
 pub(crate) fn test(args: TokenStream, item: TokenStream, rt_multi_thread: bool) -> TokenStream {
     // If any of the steps for this macro fail, we still want to expand to an item that is as close
     // to the expected output as possible. This helps out IDEs such that completions and other
@@ -450,8 +479,8 @@ pub(crate) fn test(args: TokenStream, item: TokenStream, rt_multi_thread: bool)
         Ok(it) => it,
         Err(e) => return token_stream_with_error(item, e),
     };
-    let config = if let Some(attr) = input.attrs().find(|attr| attr.meta.path().is_ident("test")) {
-        let msg = "second test attribute is supplied";
+    let config = if let Some(attr) = input.attrs().find(|attr| is_test_attribute(attr)) {
+        let msg = "second test attribute is supplied, consider removing or changing the order of your test attributes";
         Err(syn::Error::new_spanned(attr, msg))
     } else {
         AttributeArgs::parse_terminated
@@ -492,13 +521,11 @@ impl ItemFn {
     /// Convert our local function item into a token stream.
     fn into_tokens(
         self,
-        header: proc_macro2::TokenStream,
+        generated_attrs: proc_macro2::TokenStream,
         body: proc_macro2::TokenStream,
         last_block: proc_macro2::TokenStream,
     ) -> TokenStream {
         let mut tokens = proc_macro2::TokenStream::new();
-        header.to_tokens(&mut tokens);
-
         // Outer attributes are simply streamed as-is.
         for attr in self.outer_attrs {
             attr.to_tokens(&mut tokens);
@@ -512,6 +539,9 @@ impl ItemFn {
             attr.to_tokens(&mut tokens);
         }
 
+        // Add generated macros at the end, so macros processed later are aware of them.
+        generated_attrs.to_tokens(&mut tokens);
+
         self.vis.to_tokens(&mut tokens);
         self.sig.to_tokens(&mut tokens);