Add support for trait-variant

Author: lasantosr

mockall/Cargo.toml

@@ -46,6 +46,7 @@ predicates-tree = "1.0"
 mockall_derive = { version = "=0.13.1", path = "../mockall_derive" }
 
 [dev-dependencies]
+trait-variant = "0.1.2"
 async-trait = "0.1.38"
 auto_enums = "0.8.5"
 futures = "0.3.7"

mockall/src/lib.rs

@@ -1067,15 +1067,14 @@
 //!
 //! ## Async Traits
 //!
-//! Async traits aren't yet (as of 1.47.0) a part of the Rust language.  But
-//! they're available from the
-//! [`async_trait`](https://docs.rs/async-trait/0.1.38/async_trait/) crate.
-//! Mockall is compatible with this crate, with two important limitations:
-//!
-//! * The `#[automock]` attribute must appear _before_ the `#[async_trait]`
-//! attribute.
-//!
-//! * The `#[async_trait]` macro must be imported with its canonical name.
+//! Partial support for async traits was introduced in the Rust language since
+//! 1.75.0.
+//! Mockall is compatible with them, as well as both 
+//! [`async_trait`](https://docs.rs/async-trait/latest/async_trait/) and
+//! [`trait_variant`](https://docs.rs/trait-variant/latest/trait_variant/)
+//! crates, with an important limitation:
+//! 
+//! * The `#[automock]` attribute must appear _before_ the crate's attribute.
 //!
 //! ```
 //! # use async_trait::async_trait;

mockall/tests/automock_trait_variant.rs

@@ -0,0 +1,30 @@
+// vim: tw=80
+//! An async trait, for use with Futures
+#![deny(warnings)]
+
+use futures::executor::block_on;
+use mockall::*;
+
+#[automock]
+#[trait_variant::make(Send)]
+pub trait Foo {
+    async fn foo(&self) -> u32;
+    async fn bar() -> u32;
+}
+
+
+#[test]
+fn return_const() {
+    let mut mock = MockFoo::new();
+    mock.expect_foo()
+        .return_const(42u32);
+    assert_eq!(block_on(mock.foo()), 42);
+}
+
+#[test]
+fn static_method() {
+    let ctx = MockFoo::bar_context();
+    ctx.expect()
+        .return_const(42u32);
+    assert_eq!(block_on(MockFoo::bar()), 42);
+}

mockall/tests/mock_trait_variant.rs

@@ -0,0 +1,27 @@
+// vim: tw=80
+//! An async trait, for use with Futures
+#![deny(warnings)]
+
+use futures::executor::block_on;
+use mockall::*;
+
+#[trait_variant::make(Send)]
+pub trait Foo {
+    async fn foo(&self) -> u32;
+}
+
+mock! {
+    pub Bar { }
+    #[trait_variant::make(Send)]
+    impl Foo for Bar {
+        async fn foo(&self) -> u32;
+    }
+}
+
+#[test]
+fn return_const() {
+    let mut mock = MockBar::new();
+    mock.expect_foo()
+        .return_const(42u32);
+    assert_eq!(block_on(mock.foo()), 42);
+}

mockall_derive/src/lib.rs

@@ -774,6 +774,7 @@ fn find_lifetimes(ty: &Type) -> HashSet<Lifetime> {
 struct AttrFormatter<'a>{
     attrs: &'a [Attribute],
     async_trait: bool,
+    trait_variant: bool,
     doc: bool,
     must_use: bool,
 }
@@ -783,6 +784,7 @@ impl<'a> AttrFormatter<'a> {
         Self {
             attrs,
             async_trait: true,
+            trait_variant: false,
             doc: true,
             must_use: false,
         }
@@ -793,6 +795,11 @@ impl<'a> AttrFormatter<'a> {
         self
     }
 
+    fn trait_variant(&mut self, allowed: bool) -> &mut Self {
+        self.trait_variant = allowed;
+        self
+    }
+
     fn doc(&mut self, allowed: bool) -> &mut Self {
         self.doc = allowed;
         self
@@ -823,6 +830,8 @@ impl<'a> AttrFormatter<'a> {
                     self.doc
                 } else if *i.as_ref().unwrap() == "async_trait" {
                     self.async_trait
+                } else if *i.as_ref().unwrap() == "make" {
+                    self.trait_variant
                 } else if *i.as_ref().unwrap() == "expect" {
                     // This probably means that there's a lint that needs to be
                     // surpressed for the real code, but not for the mock code.

mockall_derive/src/mockable_struct.rs

@@ -371,6 +371,7 @@ impl From<(Attrs, ItemTrait)> for MockableStruct {
         let mut attrs = AttrFormatter::new(&trait_.attrs)
             .doc(true)
             .async_trait(true)
+            .trait_variant(true)
             .must_use(false)
             .format();
         attrs.push(derive_debug());