Make source_stem required for Rust SourceProviders

This removes ambiguity for developers with the 'stem' property.

Bug: 159064919
Test: New Soong test; error is produced if this property is undefined.
Change-Id: I790fbcfa6cd7dbf6df63b5cf5c22983426ec072e

1 files changed, 31 insertions, 0 deletions

diff --git a/rust/source_provider_test.go b/rust/source_provider_test.go
new file mode 100644
index 000000000..6e68ae62c
--- /dev/null
+++ b/rust/source_provider_test.go
@@ -0,0 +1,31 @@
+// Copyright 2020 The Android Open Source Project
+//
+// 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.
+
+package rust
+
+import (
+	"testing"
+)
+
+var stemRequiredError = "source_stem property is undefined but required for rust_bindgen modules"
+
+func TestSourceProviderRequiredFields(t *testing.T) {
+	testRustError(t, stemRequiredError, `
+		rust_bindgen {
+			name: "libbindgen",
+			wrapper_src: "src/any.h",
+			crate_name: "bindgen",
+		}
+	`)
+}