ui-tests: Check empty impl_runtime_apis

Signed-off-by: Alexandru Vasile <[email protected]>

frame/support/test/tests/impl_runtime_apis_ui.rs

@@ -0,0 +1,35 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#[rustversion::attr(not(stable), ignore)]
+#[cfg(not(feature = "disable-ui-tests"))]
+#[test]
+fn impl_runtime_apis_ui() {
+	// Only run the ui tests when `RUN_UI_TESTS` is set.
+	if std::env::var("RUN_UI_TESTS").is_err() {
+		return
+	}
+
+	// As trybuild is using `cargo check`, we don't need the real WASM binaries.
+	std::env::set_var("SKIP_WASM_BUILD", "1");
+
+	// Deny all warnings since we emit warnings as part of a Pallet's UI.
+	std::env::set_var("RUSTFLAGS", "--deny warnings");
+
+	let t = trybuild::TestCases::new();
+	t.compile_fail("tests/impl_runtime_apis_ui/*.rs");
+}

frame/support/test/tests/impl_runtime_apis_ui/empty_runtime_apis.rs

@@ -0,0 +1,13 @@
+use frame_support::impl_runtime_apis;
+
+// Do not use `construct_runtime!`.
+struct Runtime;
+
+// Empty `impl_runtime_apis!` cannot deduce the Runtime name
+// and should not implement the `runtime_metadata()` method.
+impl_runtime_apis! {}
+
+// Expect the test to compile because this has the effect of
+// not calling `construct_runtime!` nor `impl_runtime_apis!`
+// for the Runtime.
+fn main() {}