Add modules for converting java modules between host and device

java_device_for_host and java_host_for_device allow treating a
device module as a host module and vice versa.  They will be useful
for converting layoutlib and robolectric to Soong, as these modules
run device java code on the host.

Bug: 117920228
Test: device_host_converter_test.go
Change-Id: Ia9a371fb41a97bc16338097f3ce8b40099744167

java/device_host_converter.go

@@ -0,0 +1,131 @@
+// Copyright 2019 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 java
+
+import (
+	"android/soong/android"
+
+	"github.com/google/blueprint"
+)
+
+type DeviceHostConverter struct {
+	android.ModuleBase
+	android.DefaultableModuleBase
+
+	properties DeviceHostConverterProperties
+
+	headerJars                    android.Paths
+	implementationJars            android.Paths
+	implementationAndResourceJars android.Paths
+	resourceJars                  android.Paths
+}
+
+type DeviceHostConverterProperties struct {
+	// List of modules whose contents will be visible to modules that depend on this module.
+	Libs []string
+}
+
+type DeviceForHost struct {
+	DeviceHostConverter
+}
+
+// java_device_for_host makes the classes.jar output of a device java_library module available to host
+// java_library modules.
+//
+// It is rarely necessary, and its used is restricted to a few whitelisted projects.
+func DeviceForHostFactory() android.Module {
+	module := &DeviceForHost{}
+
+	module.AddProperties(&module.properties)
+
+	InitJavaModule(module, android.HostSupported)
+	return module
+}
+
+type HostForDevice struct {
+	DeviceHostConverter
+}
+
+// java_host_for_device makes the classes.jar output of a host java_library module available to device
+// java_library modules.
+//
+// It is rarely necessary, and its used is restricted to a few whitelisted projects.
+func HostForDeviceFactory() android.Module {
+	module := &HostForDevice{}
+
+	module.AddProperties(&module.properties)
+
+	InitJavaModule(module, android.DeviceSupported)
+	return module
+}
+
+var deviceHostConverterDepTag = dependencyTag{name: "device_host_converter"}
+
+func (d *DeviceForHost) DepsMutator(ctx android.BottomUpMutatorContext) {
+	variation := []blueprint.Variation{{Mutator: "arch", Variation: "android_common"}}
+	ctx.AddFarVariationDependencies(variation, deviceHostConverterDepTag, d.properties.Libs...)
+}
+
+func (d *HostForDevice) DepsMutator(ctx android.BottomUpMutatorContext) {
+	variation := []blueprint.Variation{{Mutator: "arch", Variation: ctx.Config().BuildOsCommonVariant}}
+	ctx.AddFarVariationDependencies(variation, deviceHostConverterDepTag, d.properties.Libs...)
+}
+
+func (d *DeviceHostConverter) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	if len(d.properties.Libs) < 1 {
+		ctx.PropertyErrorf("libs", "at least one dependency is required")
+	}
+
+	ctx.VisitDirectDepsWithTag(deviceHostConverterDepTag, func(m android.Module) {
+		if dep, ok := m.(Dependency); ok {
+			d.headerJars = append(d.headerJars, dep.HeaderJars()...)
+			d.implementationJars = append(d.implementationJars, dep.ImplementationJars()...)
+			d.implementationAndResourceJars = append(d.implementationAndResourceJars, dep.ImplementationAndResourcesJars()...)
+			d.resourceJars = append(d.resourceJars, dep.ResourceJars()...)
+		} else {
+			ctx.PropertyErrorf("libs", "module %q cannot be used as a dependency", ctx.OtherModuleName(m))
+		}
+	})
+}
+
+var _ Dependency = (*DeviceHostConverter)(nil)
+
+func (d *DeviceHostConverter) HeaderJars() android.Paths {
+	return d.headerJars
+}
+
+func (d *DeviceHostConverter) ImplementationJars() android.Paths {
+	return d.implementationJars
+}
+
+func (d *DeviceHostConverter) ResourceJars() android.Paths {
+	return d.resourceJars
+}
+
+func (d *DeviceHostConverter) ImplementationAndResourcesJars() android.Paths {
+	return d.implementationAndResourceJars
+}
+
+func (d *DeviceHostConverter) DexJar() android.Path {
+	return nil
+}
+
+func (d *DeviceHostConverter) AidlIncludeDirs() android.Paths {
+	return nil
+}
+
+func (d *DeviceHostConverter) ExportedSdkLibs() []string {
+	return nil
+}