fix: improve compatibility among test proc macros

This pr proposes a generic mechanism among different test proc macros to
avoid to generate multiple `[::core::prelude::v1::test]` on test method.

`proc_macro_attribute` function is fed with tokens after its attribute
and no tokens before it.

Give the above, this pr proposes test proc macros to append newly
generated macros after existing ones. This way, proc macros processed
later can read all macros including generated and handwritten and make
further decisions. Specifically, proc macros can append
`#[::core::prelude::v1::test]` only if it does not exist.

Macros that transform test method signature can append
`#[::core::prelude::v1::test]` directly without checking its existence
once they generate valid signature for test method.

Closes frondeus#101, frondeus#146.

crates/test-case-core/src/test_case.rs

@@ -5,7 +5,38 @@ use proc_macro2::{Span as Span2, TokenStream as TokenStream2};
 use quote::quote;
 use syn::parse::{Parse, ParseStream};
 use syn::punctuated::Punctuated;
-use syn::{parse_quote, Error, Expr, Ident, ItemFn, ReturnType, Token};
+use syn::{parse_quote, Attribute, Error, Expr, Ident, ItemFn, ReturnType, Token};
+
+// 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,
+    };
+    const CANDIDATES_LEN: usize = 4;
+
+    let candidates: [[&str; CANDIDATES_LEN]; 2] = [
+        ["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)
+        })
+    })
+}
 
 #[derive(Debug)]
 pub struct TestCase {
@@ -99,7 +130,12 @@ impl TestCase {
                 quote! { let _result = super::#item_name(#(#arg_values),*).await; },
             )
         } else {
-            attrs.insert(0, parse_quote! { #[::core::prelude::v1::test] });
+            let qualified_test_attr = parse_quote! { #[::core::prelude::v1::test] };
+            if let Some(attr) = attrs.iter().find(|attr| is_test_attribute(attr)) {
+                let msg = "second test attribute is supplied, consider removing or changing the order of your test attributes";
+                return Error::new_spanned(attr, msg).into_compile_error();
+            }
+            attrs.push(qualified_test_attr);
             (
                 TokenStream2::new(),
                 quote! { let _result = super::#item_name(#(#arg_values),*); },

crates/test-case-macros/src/lib.rs

@@ -110,7 +110,7 @@ fn expand_additional_test_case_macros(item: &mut ItemFn) -> syn::Result<Vec<(Tes
     }
 
     for i in attrs_to_remove.into_iter().rev() {
-        item.attrs.swap_remove(i);
+        item.attrs.remove(i);
     }
 
     Ok(additional_cases)

tests/acceptance_tests.rs

@@ -22,7 +22,7 @@ macro_rules! run_acceptance_test {
 
             let output = sanitize_lines(output);
 
-            insta::assert_display_snapshot!(output);
+            insta::assert_snapshot!(output);
         })
     };
     ($case_name:expr) => {

tests/snapshots/rust-nightly/acceptance__matrices_compilation_errors.snap

@@ -5,6 +5,6 @@ expression: output
 error: All literal values must be of the same type
 error: Range bounds can only be an integer literal
 error: Unbounded ranges are not supported
-error: could not compile `matrices_compilation_errors` (lib test) due to 5 previous errors
+error: could not compile `matrices_compilation_errors` (lib test) due to 5 previous errors; 1 warning emitted
 error: number too large to fit in target type
 error[E0308]: mismatched types

tests/snapshots/rust-stable/acceptance__features_produce_human_readable_errors.snap

@@ -3,4 +3,4 @@ source: tests/acceptance_tests.rs
 expression: output
 ---
 error: 'with-regex' feature is required to use 'matches-regex' keyword
-error: could not compile `features_produce_human_readable_errors` (lib test) due to previous error
+error: could not compile `features_produce_human_readable_errors` (lib test) due to 1 previous error

tests/snapshots/rust-stable/acceptance__matrices_compilation_errors.snap

@@ -5,6 +5,6 @@ expression: output
 error: All literal values must be of the same type
 error: Range bounds can only be an integer literal
 error: Unbounded ranges are not supported
-error: could not compile `matrices_compilation_errors` (lib test) due to 5 previous errors
+error: could not compile `matrices_compilation_errors` (lib test) due to 5 previous errors; 1 warning emitted
 error: number too large to fit in target type
 error[E0308]: mismatched types