Revert "Revert "Limit System SDK to 34 for Java modules in the v..."

Revert submission 2897568-revert-2894701-limit_systemsdk-WNEMOTGMRS

Reason for revert: Forward fix was merged

Reverted changes: /q/submissionid:2897568-revert-2894701-limit_systemsdk-WNEMOTGMRS

Change-Id: Id857406513fbf33a20e5d3836742ebd8a0105516
diff --git a/android/sdk_version.go b/android/sdk_version.go
index aafcee7..9c84a27 100644
--- a/android/sdk_version.go
+++ b/android/sdk_version.go
@@ -16,6 +16,7 @@
 
 import (
 	"fmt"
+	"reflect"
 	"strconv"
 	"strings"
 )
@@ -162,6 +163,17 @@
 	// If BOARD_CURRENT_API_LEVEL_FOR_VENDOR_MODULES has a numeric value,
 	// use it instead of "current" for the vendor partition.
 	currentSdkVersion := ctx.DeviceConfig().CurrentApiLevelForVendorModules()
+	// b/314011075: special case for Java modules in vendor partition. They can no longer use
+	// SDK 35 or later. Their maximum API level is limited to 34 (Android U). This is to
+	// discourage the use of Java APIs in the vendor partition which hasn't been officially
+	// supported since the Project Treble back in Android 10. We would like to eventually
+	// evacuate all Java modules from the partition, but that shall be done progressively.
+	// Note that the check for the availability of SDK 34 is to not break existing tests where
+	// any of the frozen SDK version is unavailable.
+	if isJava(ctx.Module()) && isSdkVersion34AvailableIn(ctx.Config()) {
+		currentSdkVersion = "34"
+	}
+
 	if currentSdkVersion == "current" {
 		return s
 	}
@@ -290,28 +302,79 @@
 	}
 }
 
+// Checks if the use of this SDK `s` is valid for the given module context `ctx`.
 func (s SdkSpec) ValidateSystemSdk(ctx EarlyModuleContext) bool {
-	// Ensures that the specified system SDK version is one of BOARD_SYSTEMSDK_VERSIONS (for vendor/product Java module)
-	// Assuming that BOARD_SYSTEMSDK_VERSIONS := 28 29,
-	// sdk_version of the modules in vendor/product that use system sdk must be either system_28, system_29 or system_current
-	if s.Kind != SdkSystem || s.ApiLevel.IsPreview() {
+	// Do some early checks. This check is currently only for Java modules. And our only concern
+	// is the use of "system" SDKs.
+	if !isJava(ctx.Module()) || s.Kind != SdkSystem {
 		return true
 	}
-	allowedVersions := ctx.DeviceConfig().PlatformSystemSdkVersions()
-	if ctx.DeviceSpecific() || ctx.SocSpecific() || (ctx.ProductSpecific() && ctx.Config().EnforceProductPartitionInterface()) {
-		systemSdkVersions := ctx.DeviceConfig().SystemSdkVersions()
-		if len(systemSdkVersions) > 0 {
-			allowedVersions = systemSdkVersions
+
+	inVendor := ctx.DeviceSpecific() || ctx.SocSpecific()
+	inProduct := ctx.ProductSpecific()
+	isProductUnbundled := ctx.Config().EnforceProductPartitionInterface()
+	inApex := false
+	if am, ok := ctx.Module().(ApexModule); ok {
+		inApex = am.InAnyApex()
+	}
+	isUnbundled := inVendor || (inProduct && isProductUnbundled) || inApex
+
+	// Bundled modules can use any SDK
+	if !isUnbundled {
+		return true
+	}
+
+	// Unbundled modules are allowed to use BOARD_SYSTEMSDK_VERSIONS
+	supportedVersions := ctx.DeviceConfig().SystemSdkVersions()
+
+	// b/314011075: special case for vendor modules. Java modules in the vendor partition can
+	// not use SDK 35 or later. This is to discourage the use of Java APIs in the vendor
+	// partition which hasn't been officially supported since the Project Treble back in Android
+	// 10. We would like to eventually evacuate all Java modules from the partition, but that
+	// shall be done progressively.
+	if inVendor {
+		// 28 was the API when BOARD_SYSTEMSDK_VERSIONS was introduced, so that's the oldest
+		// we should allow.
+		supportedVersions = []string{}
+		for v := 28; v <= 34; v++ {
+			supportedVersions = append(supportedVersions, strconv.Itoa(v))
 		}
 	}
-	if len(allowedVersions) > 0 && !InList(s.ApiLevel.String(), allowedVersions) {
+
+	// APEXes in the system partition are still considered as part of the platform, thus can use
+	// more SDKs from PLATFORM_SYSTEMSDK_VERSIONS
+	if inApex && !inVendor {
+		supportedVersions = ctx.DeviceConfig().PlatformSystemSdkVersions()
+	}
+
+	thisVer, err := s.EffectiveVersion(ctx)
+	if err != nil {
+		ctx.PropertyErrorf("sdk_version", "invalid sdk version %q", s.Raw)
+		return false
+	}
+
+	thisVerString := strconv.Itoa(thisVer.FinalOrPreviewInt())
+	if thisVer.IsPreview() {
+		thisVerString = *ctx.Config().productVariables.Platform_sdk_version_or_codename
+	}
+
+	if !InList(thisVerString, supportedVersions) {
 		ctx.PropertyErrorf("sdk_version", "incompatible sdk version %q. System SDK version should be one of %q",
-			s.Raw, allowedVersions)
+			s.Raw, supportedVersions)
 		return false
 	}
 	return true
 }
 
+func isJava(m Module) bool {
+	moduleType := reflect.TypeOf(m).String()
+	return strings.HasPrefix(moduleType, "*java.")
+}
+
+func isSdkVersion34AvailableIn(c Config) bool {
+	return c.PlatformSdkVersion().FinalInt() >= 34
+}
+
 func init() {
 	RegisterMakeVarsProvider(pctx, javaSdkMakeVars)
 }