android/proto.go

// Copyright 2017 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 android

import (
	"strings"

	"android/soong/bazel"

	"github.com/google/blueprint"
	"github.com/google/blueprint/proptools"
)

const (
	canonicalPathFromRootDefault = true
)

// TODO(ccross): protos are often used to communicate between multiple modules.  If the only
// way to convert a proto to source is to reference it as a source file, and external modules cannot
// reference source files in other modules, then every module that owns a proto file will need to
// export a library for every type of external user (lite vs. full, c vs. c++ vs. java).  It would
// be better to support a proto module type that exported a proto file along with some include dirs,
// and then external modules could depend on the proto module but use their own settings to
// generate the source.

type ProtoFlags struct {
	Flags                 []string
	CanonicalPathFromRoot bool
	Dir                   ModuleGenPath
	SubDir                ModuleGenPath
	OutTypeFlag           string
	OutParams             []string
	Deps                  Paths
}

type protoDependencyTag struct {
	blueprint.BaseDependencyTag
	name string
}

var ProtoPluginDepTag = protoDependencyTag{name: "plugin"}

func ProtoDeps(ctx BottomUpMutatorContext, p *ProtoProperties) {
	if String(p.Proto.Plugin) != "" && String(p.Proto.Type) != "" {
		ctx.ModuleErrorf("only one of proto.type and proto.plugin can be specified.")
	}

	if plugin := String(p.Proto.Plugin); plugin != "" {
		ctx.AddFarVariationDependencies(ctx.Config().BuildOSTarget.Variations(),
			ProtoPluginDepTag, "protoc-gen-"+plugin)
	}
}

func GetProtoFlags(ctx ModuleContext, p *ProtoProperties) ProtoFlags {
	var flags []string
	var deps Paths

	if len(p.Proto.Local_include_dirs) > 0 {
		localProtoIncludeDirs := PathsForModuleSrc(ctx, p.Proto.Local_include_dirs)
		flags = append(flags, JoinWithPrefix(localProtoIncludeDirs.Strings(), "-I"))
	}
	if len(p.Proto.Include_dirs) > 0 {
		rootProtoIncludeDirs := PathsForSource(ctx, p.Proto.Include_dirs)
		flags = append(flags, JoinWithPrefix(rootProtoIncludeDirs.Strings(), "-I"))
	}

	ctx.VisitDirectDepsWithTag(ProtoPluginDepTag, func(dep Module) {
		if hostTool, ok := dep.(HostToolProvider); !ok || !hostTool.HostToolPath().Valid() {
			ctx.PropertyErrorf("proto.plugin", "module %q is not a host tool provider",
				ctx.OtherModuleName(dep))
		} else {
			plugin := String(p.Proto.Plugin)
			deps = append(deps, hostTool.HostToolPath().Path())
			flags = append(flags, "--plugin=protoc-gen-"+plugin+"="+hostTool.HostToolPath().String())
		}
	})

	var protoOutFlag string
	if plugin := String(p.Proto.Plugin); plugin != "" {
		protoOutFlag = "--" + plugin + "_out"
	}

	return ProtoFlags{
		Flags:                 flags,
		Deps:                  deps,
		OutTypeFlag:           protoOutFlag,
		CanonicalPathFromRoot: proptools.BoolDefault(p.Proto.Canonical_path_from_root, canonicalPathFromRootDefault),
		Dir:                   PathForModuleGen(ctx, "proto"),
		SubDir:                PathForModuleGen(ctx, "proto", ctx.ModuleDir()),
	}
}

type ProtoProperties struct {
	Proto struct {
		// Proto generator type.  C++: full or lite.  Java: micro, nano, stream, or lite.
		Type *string `android:"arch_variant"`

		// Proto plugin to use as the generator.  Must be a cc_binary_host module.
		Plugin *string `android:"arch_variant"`

		// list of directories that will be added to the protoc include paths.
		Include_dirs []string

		// list of directories relative to the bp file that will
		// be added to the protoc include paths.
		Local_include_dirs []string

		// whether to identify the proto files from the root of the
		// source tree (the original method in Android, useful for
		// android-specific protos), or relative from where they were
		// specified (useful for external/third party protos).
		//
		// This defaults to true today, but is expected to default to
		// false in the future.
		Canonical_path_from_root *bool
	} `android:"arch_variant"`
}

func ProtoRule(rule *RuleBuilder, protoFile Path, flags ProtoFlags, deps Paths,
	outDir WritablePath, depFile WritablePath, outputs WritablePaths) {

	var protoBase string
	if flags.CanonicalPathFromRoot {
		protoBase = "."
	} else {
		rel := protoFile.Rel()
		protoBase = strings.TrimSuffix(protoFile.String(), rel)
	}

	rule.Command().
		BuiltTool("aprotoc").
		FlagWithArg(flags.OutTypeFlag+"=", strings.Join(flags.OutParams, ",")+":"+outDir.String()).
		FlagWithDepFile("--dependency_out=", depFile).
		FlagWithArg("-I ", protoBase).
		Flags(flags.Flags).
		Input(protoFile).
		Implicits(deps).
		ImplicitOutputs(outputs)

	rule.Command().
		BuiltTool("dep_fixer").Flag(depFile.String())
}

// Bp2buildProtoInfo contains information necessary to pass on to language specific conversion.
type Bp2buildProtoInfo struct {
	Type *string
	Name string
}

type protoAttrs struct {
	Srcs                bazel.LabelListAttribute
	Strip_import_prefix *string
	Deps                bazel.LabelListAttribute
}

// For each package in the include_dirs property a proto_library target should
// be added to the BUILD file in that package and a mapping should be added here
var includeDirsToProtoDeps = map[string]string{
	"external/protobuf/src": "//external/protobuf:libprotobuf-proto",
}

// Bp2buildProtoProperties converts proto properties, creating a proto_library and returning the
// information necessary for language-specific handling.
func Bp2buildProtoProperties(ctx Bp2buildMutatorContext, m *ModuleBase, srcs bazel.LabelListAttribute) (Bp2buildProtoInfo, bool) {
	var info Bp2buildProtoInfo
	if srcs.IsEmpty() {
		return info, false
	}

	info.Name = m.Name() + "_proto"
	attrs := protoAttrs{
		Srcs: srcs,
	}

	for axis, configToProps := range m.GetArchVariantProperties(ctx, &ProtoProperties{}) {
		for _, rawProps := range configToProps {
			var props *ProtoProperties
			var ok bool
			if props, ok = rawProps.(*ProtoProperties); !ok {
				ctx.ModuleErrorf("Could not cast ProtoProperties to expected type")
			}
			if axis == bazel.NoConfigAxis {
				info.Type = props.Proto.Type

				if !proptools.BoolDefault(props.Proto.Canonical_path_from_root, canonicalPathFromRootDefault) {
					// an empty string indicates to strips the package path
					path := ""
					attrs.Strip_import_prefix = &path
				}

				for _, dir := range props.Proto.Include_dirs {
					if dep, ok := includeDirsToProtoDeps[dir]; ok {
						attrs.Deps.Add(bazel.MakeLabelAttribute(dep))
					} else {
						ctx.PropertyErrorf("Could not find the proto_library target for include dir", dir)
					}
				}
			} else if props.Proto.Type != info.Type && props.Proto.Type != nil {
				ctx.ModuleErrorf("Cannot handle arch-variant types for protos at this time.")
			}
		}
	}

	ctx.CreateBazelTargetModule(
		bazel.BazelTargetModuleProperties{Rule_class: "proto_library"},
		CommonAttributes{Name: info.Name},
		&attrs)

	return info, true
}