Build rules for compat config docs generation.

We add a compat config build rule to extract the merged config, and
then update the droiddoc build rule to consume that.

Test: m -j offline-sdk-docs
Bug: 144927670
Change-Id: Ib1e85f97895c89227882e665572bda9bfc2a8cba
Exempt-From-Owner-Approval: ag/10097965 approved internally, Colin requested to patch to aosp

java/droiddoc.go

@@ -223,6 +223,9 @@ type DroiddocProperties struct {
 
 	// if set to true, generate docs through Dokka instead of Doclava.
 	Dokka_enabled *bool
+
+	// Compat config XML. Generates compat change documentation if set.
+	Compat_config *string `android:"path"`
 }
 
 type DroidstubsProperties struct {
@@ -1037,6 +1040,11 @@ func (d *Droiddoc) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 
 	cmd.Flag(d.Javadoc.args).Implicits(d.Javadoc.argFiles)
 
+	if d.properties.Compat_config != nil {
+		compatConfig := android.PathForModuleSrc(ctx, String(d.properties.Compat_config))
+		cmd.FlagWithInput("-compatconfig ", compatConfig)
+	}
+
 	var desc string
 	if Bool(d.properties.Dokka_enabled) {
 		desc = "dokka"

java/platform_compat_config.go

@@ -16,11 +16,17 @@ package java
 
 import (
 	"android/soong/android"
+	"fmt"
 )
 
 func init() {
 	android.RegisterSingletonType("platform_compat_config_singleton", platformCompatConfigSingletonFactory)
 	android.RegisterModuleType("platform_compat_config", platformCompatConfigFactory)
+	android.RegisterModuleType("global_compat_config", globalCompatConfigFactory)
+}
+
+func platformCompatConfigPath(ctx android.PathContext) android.OutputPath {
+	return android.PathForOutput(ctx, "compat_config", "merged_compat_config.xml")
 }
 
 type platformCompatConfigSingleton struct {
@@ -68,7 +74,7 @@ func (p *platformCompatConfigSingleton) GenerateBuildActions(ctx android.Singlet
 	}
 
 	rule := android.NewRuleBuilder()
-	outputPath := android.PathForOutput(ctx, "compat_config", "merged_compat_config.xml")
+	outputPath := platformCompatConfigPath(ctx)
 
 	rule.Command().
 		BuiltTool(ctx, "process-compat-config").
@@ -130,3 +136,49 @@ func platformCompatConfigFactory() android.Module {
 	android.InitAndroidArchModule(module, android.DeviceSupported, android.MultilibFirst)
 	return module
 }
+
+//============== merged_compat_config =================
+type globalCompatConfigProperties struct {
+	// name of the file into which the metadata will be copied.
+	Filename *string
+}
+
+type globalCompatConfig struct {
+	android.ModuleBase
+
+	properties globalCompatConfigProperties
+
+	outputFilePath android.OutputPath
+}
+
+func (c *globalCompatConfig) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	filename := String(c.properties.Filename)
+
+	inputPath := platformCompatConfigPath(ctx)
+	c.outputFilePath = android.PathForModuleOut(ctx, filename).OutputPath
+
+	// This ensures that outputFilePath has the correct name for others to
+	// use, as the source file may have a different name.
+	ctx.Build(pctx, android.BuildParams{
+		Rule:   android.Cp,
+		Output: c.outputFilePath,
+		Input:  inputPath,
+	})
+}
+
+func (h *globalCompatConfig) OutputFiles(tag string) (android.Paths, error) {
+	switch tag {
+	case "":
+		return android.Paths{h.outputFilePath}, nil
+	default:
+		return nil, fmt.Errorf("unsupported module reference tag %q", tag)
+	}
+}
+
+// global_compat_config provides access to the merged compat config xml file generated by the build.
+func globalCompatConfigFactory() android.Module {
+	module := &globalCompatConfig{}
+	module.AddProperties(&module.properties)
+	android.InitAndroidArchModule(module, android.HostAndDeviceSupported, android.MultilibCommon)
+	return module
+}