Append #[::core::prelude::v1::test] only if no test macros exist

This way we could avoid duplicated test runs if `#[test]` variants
already exist

See also frondeus/test-case#101, frondeus/test-case#143 and
tokio-rs/tokio#6497.

Closes d-e-s-o#35.

Author: kezhuw

Cargo.toml

@@ -51,6 +51,7 @@ env_logger = {version = "0.11", default-features = false, optional = true}
 
 [dev-dependencies]
 logging = {version = "0.4.8", package = "log"}
+rstest = "0.25.0"
 test-case = {version = "3.1"}
-tokio = {version = "1.0", default-features = false, features = ["rt-multi-thread", "macros"]}
+tokio = {version = "1.38", default-features = false, features = ["rt-multi-thread", "macros"]}
 tracing = {version = "0.1.20"}

macros/src/lib.rs

@@ -45,13 +45,38 @@ fn parse_attrs(attrs: Vec<Attribute>) -> syn::Result<(AttributeArgs, Vec<Attribu
   }
 }
 
-fn try_test(attr: TokenStream, input: ItemFn) -> syn::Result<Tokens> {
-  let inner_test = if attr.is_empty() {
-    quote! { ::core::prelude::v1::test }
-  } else {
-    attr.into()
+// 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))
+  })
+}
 
+fn try_test(attr: TokenStream, input: ItemFn) -> syn::Result<Tokens> {
   let ItemFn {
     attrs,
     vis,
@@ -63,9 +88,23 @@ fn try_test(attr: TokenStream, input: ItemFn) -> syn::Result<Tokens> {
   let logging_init = expand_logging_init(&attribute_args);
   let tracing_init = expand_tracing_init(&attribute_args);
 
+  let (inner_test, generated_test) = if attr.is_empty() {
+    let has_test = ignored_attrs.iter().any(is_test_attribute);
+    let generated_test = if has_test {
+      quote! {}
+    } else {
+      quote! { #[::core::prelude::v1::test]}
+    };
+    (quote! {}, generated_test)
+  } else {
+    let attr = Tokens::from(attr);
+    (quote! { #[#attr] }, quote! {})
+  };
+
   let result = quote! {
-    #[#inner_test]
+    #inner_test
     #(#ignored_attrs)*
+    #generated_test
     #vis #sig {
       // We put all initialization code into a separate module here in
       // order to prevent potential ambiguities that could result in

tests/mod.rs

@@ -5,6 +5,7 @@
 
 use tokio::runtime::Builder;
 
+use rstest::rstest;
 use tracing::debug;
 use tracing::error;
 use tracing::info;
@@ -57,6 +58,49 @@ fn with_inner_test_attribute_and_test_args_and_panic(x: i8, _y: i8) {
   assert_eq!(x, 0);
 }
 
+#[test_log::test]
+#[test]
+fn with_existing_test_attribute() {}
+
+#[test_log::test]
+#[::core::prelude::v1::test]
+fn with_existing_generated_test_attribute() {}
+
+#[tokio::test]
+#[test_log::test]
+async fn with_append_test_attribute_and_async() {
+  assert_eq!(async { 42 }.await, 42)
+}
+
+#[rstest]
+#[case(-2, -4)]
+#[case(-2, -5)]
+#[test_log::test]
+fn with_append_test_attribute_and_test_args(#[case] x: i8, #[case] _y: i8) {
+  assert_eq!(x, -2);
+}
+
+#[rstest]
+#[case(-2, -4)]
+#[case(-3, -4)]
+#[test_log::test]
+// Applied to all cases, must not come before `rstest`, see https://github.com/la10736/rstest/issues/210
+#[should_panic] // https://docs.rs/rstest/0.25.0/rstest/attr.rstest.html#use-specific-case-attributes
+fn with_append_test_attribute_and_test_args_and_panic(#[case] x: i8, #[case] _y: i8) {
+  assert_eq!(x, 0);
+}
+
+#[rstest]
+#[case(-2, -4)]
+#[case(-3, -4)]
+#[tokio::test]
+#[test_log::test]
+// Applied to all cases, must not come before `rstest`, see https://github.com/la10736/rstest/issues/210
+#[should_panic] // https://docs.rs/rstest/0.25.0/rstest/attr.rstest.html#use-specific-case-attributes
+async fn with_append_test_attribute_and_test_args_and_panic_async(#[case] x: i8, #[case] _y: i8) {
+  assert_eq!(x, 0);
+}
+
 #[instrument]
 async fn instrumented(input: usize) -> usize {
   info!("input = {}", input);