bp2build: cc_object converter.

This CL introduces a basic bp2build converter for cc_object modules.
cc_objects maps cleanly to cc_library targets, but with -fnoaddrsig.

This CL also demonstrates generating include deps within a macro to
allow the cc_object compilation to depend on a relative-include header
within an include dir.

e.g. if "foo.cc" includes "android/log.h" and the latter is located at
"include/android/log.h", the autogenerated header deps would export
"android/log.h" correctly to the foo.cc upstream target.

Test: GENERATE_BAZEL_FILES=true m nothing && bp2build-sync write && bazel build //bionic/libc:crtbegin_so1

Change-Id: Ifd9e097051ec184ab0a1929d07918f0ff4f24d98

cc/object.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	"android/soong/android"
+	"android/soong/bazel"
 )
 
 //
@@ -27,6 +28,8 @@ import (
 func init() {
 	android.RegisterModuleType("cc_object", ObjectFactory)
 	android.RegisterSdkMemberType(ccObjectSdkMemberType)
+
+	android.RegisterBp2BuildMutator("cc_object", ObjectBp2Build)
 }
 
 var ccObjectSdkMemberType = &librarySdkMemberType{
@@ -82,9 +85,80 @@ func ObjectFactory() android.Module {
 	module.compiler.appendCflags([]string{"-fno-addrsig"})
 
 	module.sdkMemberTypes = []android.SdkMemberType{ccObjectSdkMemberType}
+
 	return module.Init()
 }
 
+// For bp2build conversion.
+type bazelObjectAttributes struct {
+	Srcs               bazel.LabelList
+	Copts              []string
+	Local_include_dirs []string
+}
+
+type bazelObject struct {
+	android.BazelTargetModuleBase
+	bazelObjectAttributes
+}
+
+func (m *bazelObject) Name() string {
+	return m.BaseModuleName()
+}
+
+func (m *bazelObject) GenerateAndroidBuildActions(ctx android.ModuleContext) {}
+
+func BazelObjectFactory() android.Module {
+	module := &bazelObject{}
+	module.AddProperties(&module.bazelObjectAttributes)
+	android.InitBazelTargetModule(module)
+	return module
+}
+
+// ObjectBp2Build is the bp2build converter from cc_object modules to the
+// Bazel equivalent target, plus any necessary include deps for the cc_object.
+func ObjectBp2Build(ctx android.TopDownMutatorContext) {
+	m, ok := ctx.Module().(*Module)
+	if !ok || !m.Properties.Bazel_module.Bp2build_available {
+		return
+	}
+
+	// a Module can be something other than a cc_object.
+	if ctx.ModuleType() != "cc_object" {
+		return
+	}
+
+	if m.compiler == nil {
+		// a cc_object must have access to the compiler decorator for its props.
+		ctx.ModuleErrorf("compiler must not be nil for a cc_object module")
+	}
+
+	var copts []string
+	var srcs []string
+	var localIncludeDirs []string
+	for _, props := range m.compiler.compilerProps() {
+		if baseCompilerProps, ok := props.(*BaseCompilerProperties); ok {
+			copts = baseCompilerProps.Cflags
+			srcs = baseCompilerProps.Srcs
+			localIncludeDirs = baseCompilerProps.Local_include_dirs
+			break
+		}
+	}
+
+	attrs := &bazelObjectAttributes{
+		Srcs:               android.BazelLabelForModuleSrc(ctx, srcs),
+		Copts:              copts,
+		Local_include_dirs: localIncludeDirs,
+	}
+
+	props := bazel.NewBazelTargetModuleProperties(
+		m.Name(),
+		"cc_object",
+		"//build/bazel/rules:cc_object.bzl",
+	)
+
+	ctx.CreateBazelTargetModule(BazelObjectFactory, props, attrs)
+}
+
 func (object *objectLinker) appendLdflags(flags []string) {
 	panic(fmt.Errorf("appendLdflags on objectLinker not supported"))
 }