Add rust_protobuf module.

This adds a new SourceProvider module type to handle protobuf code
generation. See the new test for an example of how to call this.

Bug: 143953733
Test: New soong tests pass.
Test: Replacing genrules in crosvm with rust_protobuf modules.
Change-Id: Ie3117129cde37b8736bc18ee09bf5cde27c01c34

1 files changed, 109 insertions, 0 deletions

diff --git a/rust/protobuf.go b/rust/protobuf.go
new file mode 100644
index 000000000..897300f19
--- /dev/null
+++ b/rust/protobuf.go
@@ -0,0 +1,109 @@
+// 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 (
+	"android/soong/android"
+)
+
+var (
+	defaultProtobufFlags = []string{""}
+)
+
+func init() {
+	android.RegisterModuleType("rust_protobuf", RustProtobufFactory)
+	android.RegisterModuleType("rust_protobuf_host", RustProtobufHostFactory)
+}
+
+var _ SourceProvider = (*protobufDecorator)(nil)
+
+type ProtobufProperties struct {
+	// Path to the proto file that will be used to generate the source
+	Proto *string `android:"path,arch_variant"`
+
+	// List of additional flags to pass to aprotoc
+	Proto_flags []string `android:"arch_variant"`
+}
+
+type protobufDecorator struct {
+	*BaseSourceProvider
+
+	Properties ProtobufProperties
+}
+
+func (proto *protobufDecorator) GenerateSource(ctx ModuleContext, deps PathDeps) android.Path {
+	var protoFlags android.ProtoFlags
+	pluginPath := ctx.Config().HostToolPath(ctx, "protoc-gen-rust")
+
+	protoFlags.OutTypeFlag = "--rust_out"
+
+	protoFlags.Flags = append(protoFlags.Flags, " --plugin="+pluginPath.String())
+	protoFlags.Flags = append(protoFlags.Flags, defaultProtobufFlags...)
+	protoFlags.Flags = append(protoFlags.Flags, proto.Properties.Proto_flags...)
+
+	protoFlags.Deps = append(protoFlags.Deps, pluginPath)
+
+	protoFile := android.OptionalPathForModuleSrc(ctx, proto.Properties.Proto)
+	if !protoFile.Valid() {
+		ctx.PropertyErrorf("proto", "invalid path to proto file")
+	}
+
+	outDir := android.PathForModuleOut(ctx)
+	depFile := android.PathForModuleOut(ctx, proto.BaseSourceProvider.getStem(ctx)+".d")
+	outputs := android.WritablePaths{android.PathForModuleOut(ctx, proto.BaseSourceProvider.getStem(ctx)+".rs")}
+
+	rule := android.NewRuleBuilder()
+	android.ProtoRule(ctx, rule, protoFile.Path(), protoFlags, protoFlags.Deps, outDir, depFile, outputs)
+	rule.Build(pctx, ctx, "protoc_"+protoFile.Path().Rel(), "protoc "+protoFile.Path().Rel())
+
+	proto.BaseSourceProvider.OutputFile = outputs[0]
+	return outputs[0]
+}
+
+func (proto *protobufDecorator) SourceProviderProps() []interface{} {
+	return append(proto.BaseSourceProvider.SourceProviderProps(), &proto.Properties)
+}
+
+func (proto *protobufDecorator) SourceProviderDeps(ctx DepsContext, deps Deps) Deps {
+	deps = proto.BaseSourceProvider.SourceProviderDeps(ctx, deps)
+	deps.Rustlibs = append(deps.Rustlibs, "libprotobuf")
+	return deps
+}
+
+// rust_protobuf generates protobuf rust code from the provided proto file. This uses the protoc-gen-rust plugin for
+// protoc. Additional flags to the protoc command can be passed via the proto_flags property. This module type will
+// create library variants that can be used as a crate dependency by adding it to the rlibs, dylibs, and rustlibs
+// properties of other modules.
+func RustProtobufFactory() android.Module {
+	module, _ := NewRustProtobuf(android.HostAndDeviceSupported)
+	return module.Init()
+}
+
+// A host-only variant of rust_protobuf. Refer to rust_protobuf for more details.
+func RustProtobufHostFactory() android.Module {
+	module, _ := NewRustProtobuf(android.HostSupported)
+	return module.Init()
+}
+
+func NewRustProtobuf(hod android.HostOrDeviceSupported) (*Module, *protobufDecorator) {
+	protobuf := &protobufDecorator{
+		BaseSourceProvider: NewSourceProvider(),
+		Properties:         ProtobufProperties{},
+	}
+
+	module := NewSourceProviderModule(hod, protobuf, false)
+
+	return module, protobuf
+}