Improve syntax for ink! e2e runtime_only attribute argument

CHANGELOG.md

@@ -12,6 +12,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Linter: Publish the linting crates on crates.io - [#2060](https://github.com/paritytech/ink/pull/2060)
 - [E2E] Added `create_call_builder` for testing existing contracts - [#2075](https://github.com/paritytech/ink/pull/2075)
 
+### Changed
+- Improve syntax for ink! e2e `runtime_only` attribute argument - [#2083](https://github.com/paritytech/ink/pull/2083)
+
 ### Fixed
 - Fix the `StorageVec` type by excluding the `len_cached` field from its type info - [#2052](https://github.com/paritytech/ink/pull/2052)
 

Cargo.toml

@@ -38,7 +38,7 @@ blake2 = { version = "0.10" }
 cargo_metadata = { version = "0.18.0" }
 cfg-if = { version = "1.0" }
 contract-build = { version = "4.0.0-rc.1" }
-darling = { version = "0.20.3" }
+darling = { version = "0.20.4" }
 derive_more = { version = "0.99.17", default-features = false }
 drink = { version = "=0.8.5" }
 either = { version = "1.5", default-features = false }

crates/e2e/macro/src/codegen.rs

@@ -71,8 +71,8 @@ impl InkE2ETest {
                 build_full_client(&environment, exec_build_contracts, node_url)
             }
             #[cfg(any(test, feature = "drink"))]
-            Backend::RuntimeOnly { runtime } => {
-                build_runtime_client(exec_build_contracts, runtime)
+            Backend::RuntimeOnly(runtime) => {
+                build_runtime_client(exec_build_contracts, runtime.into())
             }
         };
 
@@ -154,12 +154,7 @@ fn build_full_client(
 }
 
 #[cfg(any(test, feature = "drink"))]
-fn build_runtime_client(
-    contracts: TokenStream2,
-    runtime: Option<syn::Path>,
-) -> TokenStream2 {
-    let runtime =
-        runtime.unwrap_or_else(|| syn::parse_quote! { ::ink_e2e::MinimalRuntime });
+fn build_runtime_client(contracts: TokenStream2, runtime: syn::Path) -> TokenStream2 {
     quote! {
         let contracts = #contracts;
         let mut client = ::ink_e2e::DrinkClient::<_, _, #runtime>::new(contracts);

crates/e2e/macro/src/config.rs

@@ -26,7 +26,27 @@ pub enum Backend {
     /// This runs a runtime emulator within `TestExternalities` (using drink! library) in
     /// the same process as the test.
     #[cfg(any(test, feature = "drink"))]
-    RuntimeOnly { runtime: Option<syn::Path> },
+    RuntimeOnly(RuntimeOnly),
+}
+
+/// The runtime emulator that should be used within `TestExternalities` (using drink!
+/// library).
+#[cfg(any(test, feature = "drink"))]
+#[derive(Clone, Eq, PartialEq, Debug, darling::FromMeta)]
+pub enum RuntimeOnly {
+    #[darling(word)]
+    Default,
+    Runtime(syn::Path),
+}
+
+#[cfg(any(test, feature = "drink"))]
+impl From<RuntimeOnly> for syn::Path {
+    fn from(value: RuntimeOnly) -> Self {
+        match value {
+            RuntimeOnly::Default => syn::parse_quote! { ::ink_e2e::MinimalRuntime },
+            RuntimeOnly::Runtime(path) => path,
+        }
+    }
 }
 
 /// The End-to-End test configuration.
@@ -100,7 +120,7 @@ mod tests {
         let input = quote! {
             additional_contracts = "adder/Cargo.toml flipper/Cargo.toml",
             environment = crate::CustomEnvironment,
-            backend(runtime_only()),
+            backend(runtime_only),
             node_url = "ws://127.0.0.1:8000"
         };
         let config =
@@ -115,7 +135,7 @@ mod tests {
             Some(syn::parse_quote! { crate::CustomEnvironment })
         );
 
-        assert_eq!(config.backend(), Backend::RuntimeOnly { runtime: None });
+        assert_eq!(config.backend(), Backend::RuntimeOnly(RuntimeOnly::Default));
         assert_eq!(config.node_url(), Some(String::from("ws://127.0.0.1:8000")));
 
         std::env::set_var("CONTRACTS_NODE_URL", "ws://127.0.0.1:9000");
@@ -132,9 +152,9 @@ mod tests {
 
         assert_eq!(
             config.backend(),
-            Backend::RuntimeOnly {
-                runtime: Some(syn::parse_quote! { ::ink_e2e::MinimalRuntime })
-            }
+            Backend::RuntimeOnly(RuntimeOnly::Runtime(
+                syn::parse_quote! { ::ink_e2e::MinimalRuntime }
+            ))
         );
         assert_eq!(config.node_url(), None)
     }

integration-tests/e2e-runtime-only-backend/lib.rs

@@ -55,7 +55,7 @@ pub mod flipper {
         /// - flip the flipper
         /// - get the flipper's value
         /// - assert that the value is `true`
-        #[ink_e2e::test(backend(runtime_only()))]
+        #[ink_e2e::test(backend(runtime_only))]
         async fn it_works<Client: E2EBackend>(mut client: Client) -> E2EResult<()> {
             // given
             const INITIAL_VALUE: bool = false;
@@ -88,7 +88,7 @@ pub mod flipper {
         /// - transfer some funds to the contract using runtime call
         /// - get the contract's balance again
         /// - assert that the contract's balance increased by the transferred amount
-        #[ink_e2e::test(backend(runtime_only()))]
+        #[ink_e2e::test(backend(runtime_only))]
         async fn runtime_call_works() -> E2EResult<()> {
             // given
             let mut constructor = FlipperRef::new(false);