Improve android_app_import.dpi_variants handling.

Instead of circumventing the limitation of Prebuilt implementation by
picking a source path itself, it now uses the same mechanism as
archMutator and replaces the source path in advance so that Prebuilt
always sees the corrent source path.

Because this requires the Apk field to be a string pointer, the single
source prebuilt implementation is being updated to be reflection-based.

Test: Soong unit tests, m soong_docs, TreeHugger
Change-Id: I2304f15e32d632f74f95f0d9e9bf1f75ff3e2225

1 files changed, 40 insertions, 8 deletions

diff --git a/android/prebuilt.go b/android/prebuilt.go
index 3d9804ce..48d3b68b 100644
--- a/android/prebuilt.go
+++ b/android/prebuilt.go
@@ -16,6 +16,7 @@ package android
 
 import (
 	"fmt"
+	"reflect"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -43,7 +44,10 @@ type Prebuilt struct {
 	properties PrebuiltProperties
 	module     Module
 	srcs       *[]string
-	src        *string
+
+	// Metadata for single source Prebuilt modules.
+	srcProps reflect.Value
+	srcField reflect.StructField
 }
 
 func (p *Prebuilt) Name(name string) string {
@@ -71,11 +75,16 @@ func (p *Prebuilt) SingleSourcePath(ctx ModuleContext) Path {
 		// sources.
 		return PathForModuleSrc(ctx, (*p.srcs)[0])
 	} else {
-		if proptools.String(p.src) == "" {
-			ctx.PropertyErrorf("src", "missing prebuilt source file")
+		if !p.srcProps.IsValid() {
+			ctx.ModuleErrorf("prebuilt source was not set")
+		}
+		src := p.getSingleSourceFieldValue()
+		if src == "" {
+			ctx.PropertyErrorf(proptools.FieldNameForProperty(p.srcField.Name),
+				"missing prebuilt source file")
 			return nil
 		}
-		return PathForModuleSrc(ctx, *p.src)
+		return PathForModuleSrc(ctx, src)
 	}
 }
 
@@ -89,10 +98,12 @@ func InitPrebuiltModule(module PrebuiltInterface, srcs *[]string) {
 	p.srcs = srcs
 }
 
-func InitSingleSourcePrebuiltModule(module PrebuiltInterface, src *string) {
+func InitSingleSourcePrebuiltModule(module PrebuiltInterface, srcProps interface{}, srcField string) {
 	p := module.Prebuilt()
 	module.AddProperties(&p.properties)
-	p.src = src
+	p.srcProps = reflect.ValueOf(srcProps).Elem()
+	p.srcField, _ = p.srcProps.Type().FieldByName(srcField)
+	p.checkSingleSourceProperties()
 }
 
 type PrebuiltInterface interface {
@@ -129,7 +140,7 @@ func PrebuiltMutator(ctx BottomUpMutatorContext) {
 func PrebuiltSelectModuleMutator(ctx TopDownMutatorContext) {
 	if m, ok := ctx.Module().(PrebuiltInterface); ok && m.Prebuilt() != nil {
 		p := m.Prebuilt()
-		if p.srcs == nil && p.src == nil {
+		if p.srcs == nil && !p.srcProps.IsValid() {
 			panic(fmt.Errorf("prebuilt module did not have InitPrebuiltModule called on it"))
 		}
 		if !p.properties.SourceExists {
@@ -172,7 +183,7 @@ func (p *Prebuilt) usePrebuilt(ctx TopDownMutatorContext, source Module) bool {
 		return false
 	}
 
-	if p.src != nil && *p.src == "" {
+	if p.srcProps.IsValid() && p.getSingleSourceFieldValue() == "" {
 		return false
 	}
 
@@ -187,3 +198,24 @@ func (p *Prebuilt) usePrebuilt(ctx TopDownMutatorContext, source Module) bool {
 func (p *Prebuilt) SourceExists() bool {
 	return p.properties.SourceExists
 }
+
+func (p *Prebuilt) checkSingleSourceProperties() {
+	if !p.srcProps.IsValid() || p.srcField.Name == "" {
+		panic(fmt.Errorf("invalid single source prebuilt %+v", p))
+	}
+
+	if p.srcProps.Kind() != reflect.Struct && p.srcProps.Kind() != reflect.Interface {
+		panic(fmt.Errorf("invalid single source prebuilt %+v", p.srcProps))
+	}
+}
+
+func (p *Prebuilt) getSingleSourceFieldValue() string {
+	value := p.srcProps.FieldByIndex(p.srcField.Index)
+	if value.Kind() == reflect.Ptr {
+		value = value.Elem()
+	}
+	if value.Kind() != reflect.String {
+		panic(fmt.Errorf("prebuilt src field %q should be a string or a pointer to one", p.srcField.Name))
+	}
+	return value.String()
+}