Add rust-project.json generator

Because we are not relying on Cargo.toml for our crate dependencies,
we need to provide a structured file to rust-analyzer which describes
the locations of the crates. Add a generator for that purpose, similarly
to cc/compdb and cc/ccdeps.

Bug: 156395307
Test: SOONG_GEN_RUST_PROJECT=1 m nothing && \
      cat ${ANDROID_BUILD_TOP}/out/soong/rust-project.json
Change-Id: I46efe0adeddae281eaf86707504c3aa15b5e80b8

1 files changed, 55 insertions, 0 deletions

diff --git a/rust/project_json_test.go b/rust/project_json_test.go
new file mode 100644
index 000000000..6786e72c7
--- /dev/null
+++ b/rust/project_json_test.go
@@ -0,0 +1,55 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// 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 (
+	"io/ioutil"
+	"path/filepath"
+	"testing"
+
+	"android/soong/android"
+	"android/soong/cc"
+)
+
+func TestProjectJson(t *testing.T) {
+	bp := `rust_library {
+		  name: "liba",
+		  srcs: ["src/lib.rs"],
+		  crate_name: "a"
+		}` + GatherRequiredDepsForTest()
+	env := map[string]string{"SOONG_GEN_RUST_PROJECT": "1"}
+	fs := map[string][]byte{
+		"foo.rs":     nil,
+		"src/lib.rs": nil,
+	}
+
+	cc.GatherRequiredFilesForTest(fs)
+
+	config := android.TestArchConfig(buildDir, env, bp, fs)
+	ctx := CreateTestContext()
+	ctx.Register(config)
+	_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
+	android.FailIfErrored(t, errs)
+	_, errs = ctx.PrepareBuildActions(config)
+	android.FailIfErrored(t, errs)
+
+	// The JSON file is generated via WriteFileToOutputDir. Therefore, it
+	// won't appear in the Output of the TestingSingleton. Manually verify
+	// it exists.
+	_, err := ioutil.ReadFile(filepath.Join(buildDir, "rust-project.json"))
+	if err != nil {
+		t.Errorf("rust-project.json has not been generated")
+	}
+}