platform_build_soong/android/defaults.go

// Copyright 2015 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 (
	"github.com/google/blueprint"
	"github.com/google/blueprint/proptools"
)

type defaultsDependencyTag struct {
	blueprint.BaseDependencyTag
}

var DefaultsDepTag defaultsDependencyTag

type defaultsProperties struct {
	Defaults []string
}

type DefaultableModuleBase struct {
	defaultsProperties    defaultsProperties
	defaultableProperties []interface{}
}

func (d *DefaultableModuleBase) defaults() *defaultsProperties {
	return &d.defaultsProperties
}

func (d *DefaultableModuleBase) setProperties(props []interface{}) {
	d.defaultableProperties = props
}

// Interface that must be supported by any module to which defaults can be applied.
type Defaultable interface {
	// Get a pointer to the struct containing the Defaults property.
	defaults() *defaultsProperties

	// Set the property structures into which defaults will be added.
	setProperties([]interface{})

	// Apply defaults from the supplied Defaults to the property structures supplied to
	// setProperties(...).
	applyDefaults(TopDownMutatorContext, []Defaults)
}

type DefaultableModule interface {
	Module
	Defaultable
}

var _ Defaultable = (*DefaultableModuleBase)(nil)

func InitDefaultableModule(module DefaultableModule) {
	module.setProperties(module.(Module).GetProperties())

	module.AddProperties(module.defaults())
}

type DefaultsModuleBase struct {
	DefaultableModuleBase
}

// The common pattern for defaults modules is to register separate instances of
// the xxxProperties structs in the AddProperties calls, rather than reusing the
// ones inherited from Module.
//
// The effect is that e.g. myDefaultsModuleInstance.base().xxxProperties won't
// contain the values that have been set for the defaults module. Rather, to
// retrieve the values it is necessary to iterate over properties(). E.g. to get
// the commonProperties instance that have the real values:
//
//   d := myModule.(Defaults)
//   for _, props := range d.properties() {
//     if cp, ok := props.(*commonProperties); ok {
//       ... access property values in cp ...
//     }
//   }
//
// The rationale is that the properties on a defaults module apply to the
// defaultable modules using it, not to the defaults module itself. E.g. setting
// the "enabled" property false makes inheriting modules disabled by default,
// rather than disabling the defaults module itself.
type Defaults interface {
	Defaultable

	// Although this function is unused it is actually needed to ensure that only modules that embed
	// DefaultsModuleBase will type-assert to the Defaults interface.
	isDefaults() bool

	// Get the structures containing the properties for which defaults can be provided.
	properties() []interface{}
}

func (d *DefaultsModuleBase) isDefaults() bool {
	return true
}

func (d *DefaultsModuleBase) properties() []interface{} {
	return d.defaultableProperties
}

func (d *DefaultsModuleBase) GenerateAndroidBuildActions(ctx ModuleContext) {
}

func InitDefaultsModule(module DefaultableModule) {
	module.AddProperties(
		&hostAndDeviceProperties{},
		&commonProperties{},
		&variableProperties{})

	InitArchModule(module)
	InitDefaultableModule(module)

	// Add properties that will not have defaults applied to them.
	module.AddProperties(&module.base().nameProperties)

	module.base().module = module
}

var _ Defaults = (*DefaultsModuleBase)(nil)

func (defaultable *DefaultableModuleBase) applyDefaults(ctx TopDownMutatorContext,
	defaultsList []Defaults) {

	for _, defaults := range defaultsList {
		for _, prop := range defaultable.defaultableProperties {
			for _, def := range defaults.properties() {
				if proptools.TypeEqual(prop, def) {
					err := proptools.PrependProperties(prop, def, nil)
					if err != nil {
						if propertyErr, ok := err.(*proptools.ExtendPropertyError); ok {
							ctx.PropertyErrorf(propertyErr.Property, "%s", propertyErr.Err.Error())
						} else {
							panic(err)
						}
					}
				}
			}
		}
	}
}

func RegisterDefaultsPreArchMutators(ctx RegisterMutatorsContext) {
	ctx.BottomUp("defaults_deps", defaultsDepsMutator).Parallel()
	ctx.TopDown("defaults", defaultsMutator).Parallel()
}

func defaultsDepsMutator(ctx BottomUpMutatorContext) {
	if defaultable, ok := ctx.Module().(Defaultable); ok {
		ctx.AddDependency(ctx.Module(), DefaultsDepTag, defaultable.defaults().Defaults...)
	}
}

func defaultsMutator(ctx TopDownMutatorContext) {
	if defaultable, ok := ctx.Module().(Defaultable); ok && len(defaultable.defaults().Defaults) > 0 {
		var defaultsList []Defaults
		seen := make(map[Defaults]bool)

		ctx.WalkDeps(func(module, parent Module) bool {
			if ctx.OtherModuleDependencyTag(module) == DefaultsDepTag {
				if defaults, ok := module.(Defaults); ok {
					if !seen[defaults] {
						seen[defaults] = true
						defaultsList = append(defaultsList, defaults)
						return len(defaults.defaults().Defaults) > 0
					}
				} else {
					ctx.PropertyErrorf("defaults", "module %s is not an defaults module",
						ctx.OtherModuleName(module))
				}
			}
			return false
		})
		defaultable.applyDefaults(ctx, defaultsList)
	}
}