Merge "Refactor prebuilt to use srcs supplier function" am: 175ef303a3

Change-Id: I830bd1de9078a403d720376a518ec95ef4bdd261

android/prebuilt.go

@@ -50,12 +50,9 @@ type PrebuiltProperties struct {
 
 type Prebuilt struct {
 	properties PrebuiltProperties
-	module     Module
-	srcs       *[]string
 
-	// Metadata for single source Prebuilt modules.
-	srcProps reflect.Value
-	srcField reflect.StructField
+	srcsSupplier     PrebuiltSrcsSupplier
+	srcsPropertyName string
 }
 
 func (p *Prebuilt) Name(name string) string {
@@ -72,31 +69,26 @@ func (p *Prebuilt) ForcePrefer() {
 // preference configs. We'll want to add native support for dynamic source cases if we end up having
 // more modules like this.
 func (p *Prebuilt) SingleSourcePath(ctx ModuleContext) Path {
-	if p.srcs != nil {
-		if len(*p.srcs) == 0 {
-			ctx.PropertyErrorf("srcs", "missing prebuilt source file")
+	if p.srcsSupplier != nil {
+		srcs := p.srcsSupplier()
+
+		if len(srcs) == 0 {
+			ctx.PropertyErrorf(p.srcsPropertyName, "missing prebuilt source file")
 			return nil
 		}
 
-		if len(*p.srcs) > 1 {
-			ctx.PropertyErrorf("srcs", "multiple prebuilt source files")
+		if len(srcs) > 1 {
+			ctx.PropertyErrorf(p.srcsPropertyName, "multiple prebuilt source files")
 			return nil
 		}
 
 		// Return the singleton source after expanding any filegroup in the
 		// sources.
-		return PathForModuleSrc(ctx, (*p.srcs)[0])
-	} else {
-		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
-		}
+		src := srcs[0]
 		return PathForModuleSrc(ctx, src)
+	} else {
+		ctx.ModuleErrorf("prebuilt source was not set")
+		return nil
 	}
 }
 
@@ -104,18 +96,80 @@ func (p *Prebuilt) UsePrebuilt() bool {
 	return p.properties.UsePrebuilt
 }
 
-func InitPrebuiltModule(module PrebuiltInterface, srcs *[]string) {
+// Called to provide the srcs value for the prebuilt module.
+//
+// Return the src value or nil if it is not available.
+type PrebuiltSrcsSupplier func() []string
+
+// Initialize the module as a prebuilt module that uses the provided supplier to access the
+// prebuilt sources of the module.
+//
+// The supplier will be called multiple times and must return the same values each time it
+// is called. If it returns an empty array (or nil) then the prebuilt module will not be used
+// as a replacement for a source module with the same name even if prefer = true.
+//
+// If the Prebuilt.SingleSourcePath() is called on the module then this must return an array
+// containing exactly one source file.
+//
+// The provided property name is used to provide helpful error messages in the event that
+// a problem arises, e.g. calling SingleSourcePath() when more than one source is provided.
+func InitPrebuiltModuleWithSrcSupplier(module PrebuiltInterface, srcsSupplier PrebuiltSrcsSupplier, srcsPropertyName string) {
 	p := module.Prebuilt()
 	module.AddProperties(&p.properties)
-	p.srcs = srcs
+
+	if srcsSupplier == nil {
+		panic(fmt.Errorf("srcsSupplier must not be nil"))
+	}
+	if srcsPropertyName == "" {
+		panic(fmt.Errorf("srcsPropertyName must not be empty"))
+	}
+
+	p.srcsSupplier = srcsSupplier
+	p.srcsPropertyName = srcsPropertyName
+}
+
+func InitPrebuiltModule(module PrebuiltInterface, srcs *[]string) {
+	if srcs == nil {
+		panic(fmt.Errorf("srcs must not be nil"))
+	}
+
+	srcsSupplier := func() []string {
+		return *srcs
+	}
+
+	InitPrebuiltModuleWithSrcSupplier(module, srcsSupplier, "srcs")
 }
 
 func InitSingleSourcePrebuiltModule(module PrebuiltInterface, srcProps interface{}, srcField string) {
-	p := module.Prebuilt()
-	module.AddProperties(&p.properties)
-	p.srcProps = reflect.ValueOf(srcProps).Elem()
-	p.srcField, _ = p.srcProps.Type().FieldByName(srcField)
-	p.checkSingleSourceProperties()
+	srcPropsValue := reflect.ValueOf(srcProps).Elem()
+	srcStructField, _ := srcPropsValue.Type().FieldByName(srcField)
+	if !srcPropsValue.IsValid() || srcStructField.Name == "" {
+		panic(fmt.Errorf("invalid single source prebuilt %+v", module))
+	}
+
+	if srcPropsValue.Kind() != reflect.Struct && srcPropsValue.Kind() != reflect.Interface {
+		panic(fmt.Errorf("invalid single source prebuilt %+v", srcProps))
+	}
+
+	srcFieldIndex := srcStructField.Index
+	srcPropertyName := proptools.PropertyNameForField(srcField)
+
+	srcsSupplier := func() []string {
+		value := srcPropsValue.FieldByIndex(srcFieldIndex)
+		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 but was %d %q", srcPropertyName, value.Kind(), value))
+		}
+		src := value.String()
+		if src == "" {
+			return nil
+		}
+		return []string{src}
+	}
+
+	InitPrebuiltModuleWithSrcSupplier(module, srcsSupplier, srcPropertyName)
 }
 
 type PrebuiltInterface interface {
@@ -152,7 +206,7 @@ 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.srcProps.IsValid() {
+		if p.srcsSupplier == nil {
 			panic(fmt.Errorf("prebuilt module did not have InitPrebuiltModule called on it"))
 		}
 		if !p.properties.SourceExists {
@@ -191,11 +245,7 @@ func PrebuiltPostDepsMutator(ctx BottomUpMutatorContext) {
 // usePrebuilt returns true if a prebuilt should be used instead of the source module.  The prebuilt
 // will be used if it is marked "prefer" or if the source module is disabled.
 func (p *Prebuilt) usePrebuilt(ctx TopDownMutatorContext, source Module) bool {
-	if p.srcs != nil && len(*p.srcs) == 0 {
-		return false
-	}
-
-	if p.srcProps.IsValid() && p.getSingleSourceFieldValue() == "" {
+	if p.srcsSupplier != nil && len(p.srcsSupplier()) == 0 {
 		return false
 	}
 
@@ -210,24 +260,3 @@ 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()
-}