Prepare for a type-safe OnceKey

Add an opaque OnceKey type and use it for all calls to Once in
build/soong.  A future patch will convert the arguments to
Once* to OnceKey once users outside build/soong have been updated.

Test: onceper_test.go
Change-Id: Ifcb338e6e603e804e507203c9508d30ffb2df966

5 files changed, 9 insertions, 5 deletions

diff --git a/java/android_resources.go b/java/android_resources.go
index efd3e3dd0..44cb709e4 100644
--- a/java/android_resources.go
+++ b/java/android_resources.go
@@ -46,7 +46,7 @@ type overlayGlobResult struct {
 	paths android.DirectorySortedPaths
 }
 
-const overlayDataKey = "overlayDataKey"
+var overlayDataKey = android.NewOnceKey("overlayDataKey")
 
 type globbedResourceDir struct {
 	dir   android.Path
diff --git a/java/dexpreopt.go b/java/dexpreopt.go
index bb72b7dec..33c46f4fe 100644
--- a/java/dexpreopt.go
+++ b/java/dexpreopt.go
@@ -81,12 +81,14 @@ func (d *dexpreopter) dexpreoptDisabled(ctx android.ModuleContext) bool {
 	return false
 }
 
+var dexpreoptGlobalConfigKey = android.NewOnceKey("DexpreoptGlobalConfig")
+
 func (d *dexpreopter) dexpreopt(ctx android.ModuleContext, dexJarFile android.ModuleOutPath) android.ModuleOutPath {
 	if d.dexpreoptDisabled(ctx) {
 		return dexJarFile
 	}
 
-	globalConfig := ctx.Config().Once("DexpreoptGlobalConfig", func() interface{} {
+	globalConfig := ctx.Config().Once(dexpreoptGlobalConfigKey, func() interface{} {
 		if f := ctx.Config().DexpreoptGlobalConfig(); f != "" {
 			ctx.AddNinjaFileDeps(f)
 			globalConfig, err := dexpreopt.LoadGlobalConfig(f)
diff --git a/java/hiddenapi.go b/java/hiddenapi.go
index 983daa79c..c7eac733f 100644
--- a/java/hiddenapi.go
+++ b/java/hiddenapi.go
@@ -121,7 +121,7 @@ func hiddenAPIEncodeDex(ctx android.ModuleContext, output android.WritablePath,
 	hiddenAPISaveDexInputs(ctx, dexInput)
 }
 
-const hiddenAPIOutputsKey = "hiddenAPIOutputsKey"
+var hiddenAPIOutputsKey = android.NewOnceKey("hiddenAPIOutputsKey")
 
 var hiddenAPIOutputsLock sync.Mutex
 
diff --git a/java/sdk.go b/java/sdk.go
index 988610f5b..0959be7de 100644
--- a/java/sdk.go
+++ b/java/sdk.go
@@ -28,7 +28,7 @@ func init() {
 	android.RegisterPreSingletonType("sdk", sdkSingletonFactory)
 }
 
-const sdkSingletonKey = "sdkSingletonKey"
+var sdkSingletonKey = android.NewOnceKey("sdkSingletonKey")
 
 type sdkContext interface {
 	// sdkVersion eturns the sdk_version property of the current module, or an empty string if it is not set.
diff --git a/java/sdk_library.go b/java/sdk_library.go
index ca3131c2f..1b0fe75e0 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -627,8 +627,10 @@ func (module *sdkLibrary) ImplementationJars(ctx android.BaseContext, sdkVersion
 	}
 }
 
+var javaSdkLibrariesKey = android.NewOnceKey("javaSdkLibraries")
+
 func javaSdkLibraries(config android.Config) *[]string {
-	return config.Once("javaSdkLibraries", func() interface{} {
+	return config.Once(javaSdkLibrariesKey, func() interface{} {
 		return &[]string{}
 	}).(*[]string)
 }