feat: Support generic types in test_context macro (#44)

- Allow using test_context with generic contexts like MyContext<T>

Author: rookiecj

README.md

@@ -31,6 +31,42 @@ fn test_works(ctx: &mut MyContext) {
 }
 ```
 
+with generic types, you can use same type with different values
+
+```rust
+use test_context::{test_context, TestContext};
+use std::marker::PhantomData;
+
+struct MyGenericContext<T> {
+    value: u32,
+    _marker: PhantomData<T>,
+}
+
+impl TestContext for MyGenericContext<String> {
+    fn setup() -> MyGenericContext<String> {
+        MyGenericContext { value: 1, _marker: PhantomData }
+    }
+}
+
+#[test_context(MyGenericContext<String>)]
+#[test]
+fn test_generic_type(ctx: &mut MyGenericContext<String>) {
+    assert_eq!(ctx.value, 1);
+}
+
+impl TestContext for MyGenericContext<u32> {
+    fn setup() -> MyGenericContext<u32> {
+        MyGenericContext { value: 2, _marker: PhantomData }
+    }
+}
+
+#[test_context(MyGenericContext<u32>)]
+#[test]
+fn test_generic_type_u32(ctx: &mut MyGenericContext<u32>) {
+    assert_eq!(ctx.value, 2);
+}
+```
+
 Alternatively, you can use `async` functions in your test context by using the
 `AsyncTestContext`.
 

test-context-macros/src/args.rs

@@ -1,14 +1,14 @@
-use syn::{parse::Parse, Ident, Token};
+use syn::{parse::Parse, Token, Type};
 
 pub(crate) struct TestContextArgs {
-    pub(crate) context_type: Ident,
+    pub(crate) context_type: Type,
     pub(crate) skip_teardown: bool,
 }
 
 impl Parse for TestContextArgs {
     fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
         let mut skip_teardown = false;
-        let mut context_type: Option<Ident> = None;
+        let mut context_type: Option<Type> = None;
 
         while !input.is_empty() {
             let lookahead = input.lookahead1();
@@ -18,10 +18,8 @@ impl Parse for TestContextArgs {
                 }
                 let _ = input.parse::<kw::skip_teardown>()?;
                 skip_teardown = true;
-            } else if lookahead.peek(Ident) {
-                if context_type.is_some() {
-                    return Err(input.error("expected only a single type identifier"));
-                }
+            } else if context_type.is_none() {
+                // Parse any valid Rust type, including generic types
                 context_type = Some(input.parse()?);
             } else if lookahead.peek(Token![,]) {
                 let _ = input.parse::<Token![,]>()?;

test-context/tests/test.rs

@@ -1,3 +1,5 @@
+use std::marker::PhantomData;
+
 use test_context::{test_context, AsyncTestContext, TestContext};
 
 struct Context {
@@ -47,6 +49,43 @@ fn includes_return_value() {
     assert_eq!(return_value_func(), 1);
 }
 
+struct ContextGeneric<T> {
+    n: u32,
+    _marker: PhantomData<T>,
+}
+
+struct ContextGenericType1;
+impl TestContext for ContextGeneric<ContextGenericType1> {
+    fn setup() -> Self {
+        Self {
+            n: 1,
+            _marker: PhantomData,
+        }
+    }
+}
+
+#[test_context(ContextGeneric<ContextGenericType1>)]
+#[test]
+fn test_generic_type(ctx: &mut ContextGeneric<ContextGenericType1>) {
+    assert_eq!(ctx.n, 1);
+}
+
+struct ContextGenericType2;
+impl TestContext for ContextGeneric<ContextGenericType2> {
+    fn setup() -> Self {
+        Self {
+            n: 2,
+            _marker: PhantomData,
+        }
+    }
+}
+
+#[test_context(ContextGeneric<ContextGenericType2>)]
+#[test]
+fn test_generic_type_other(ctx: &mut ContextGeneric<ContextGenericType2>) {
+    assert_eq!(ctx.n, 2);
+}
+
 struct AsyncContext {
     n: u32,
 }