Add kotlin-lang flag.

This allows targets to choose whether they compile with kotlin 1.9
or kotlin 2

Bug: 383569207
Flag: EXEMPT this is a flag itself
Test: built system image
Change-Id: I1228ed1d8a5f9d6029261e4a867a2301069e315f

2 files changed, 20 insertions, 3 deletions

diff --git a/java/base.go b/java/base.go
index 1aef37ca4..a2fc29de7 100644
--- a/java/base.go
+++ b/java/base.go
@@ -90,6 +90,10 @@ type CommonProperties struct {
 	// list of module-specific flags that will be used for kotlinc compiles
 	Kotlincflags []string `android:"arch_variant"`
 
+	// Kotlin language version to target. Currently only 1.9 and 2 are supported.
+	// See kotlinc's `-language-version` flag.
+	Kotlin_lang_version *string
+
 	// list of java libraries that will be in the classpath
 	Libs []string `android:"arch_variant"`
 
@@ -1331,6 +1335,16 @@ func (j *Module) compile(ctx android.ModuleContext, extraSrcJars, extraClasspath
 		kotlincFlags := j.properties.Kotlincflags
 		CheckKotlincFlags(ctx, kotlincFlags)
 
+		kotlin_lang_version := proptools.StringDefault(j.properties.Kotlin_lang_version, "1.9")
+		if kotlin_lang_version == "1.9" {
+			kotlincFlags = append(kotlincFlags, "-language-version 1.9")
+		} else if kotlin_lang_version == "2" {
+			kotlincFlags = append(kotlincFlags, "-Xsuppress-version-warnings", "-Xconsistent-data-class-copy-visibility")
+		} else {
+			ctx.PropertyErrorf("kotlin_lang_version", "Must be one of `1.9` or `2`")
+
+		}
+
 		// Workaround for KT-46512
 		kotlincFlags = append(kotlincFlags, "-Xsam-conversions=class")
 
@@ -2059,7 +2073,9 @@ func CheckKotlincFlags(ctx android.ModuleContext, flags []string) {
 		} else if strings.HasPrefix(flag, "-Xintellij-plugin-root") {
 			ctx.PropertyErrorf("kotlincflags",
 				"Bad flag: `%s`, only use internal compiler for consistency.", flag)
-		} else if inList(flag, config.KotlincIllegalFlags) {
+		} else if slices.ContainsFunc(config.KotlincIllegalFlags, func(f string) bool {
+			return strings.HasPrefix(flag, f)
+		}) {
 			ctx.PropertyErrorf("kotlincflags", "Flag `%s` already used by build system", flag)
 		} else if flag == "-include-runtime" {
 			ctx.PropertyErrorf("kotlincflags", "Bad flag: `%s`, do not include runtime.", flag)
diff --git a/java/config/kotlin.go b/java/config/kotlin.go
index bf4c886d1..ffb025d9c 100644
--- a/java/config/kotlin.go
+++ b/java/config/kotlin.go
@@ -21,6 +21,7 @@ var (
 	KotlincIllegalFlags = []string{
 		"-no-jdk",
 		"-no-stdlib",
+		"-language-version",
 	}
 )
 
@@ -49,12 +50,12 @@ func init() {
 		"-J--add-opens=java.base/java.util=ALL-UNNAMED", // https://youtrack.jetbrains.com/issue/KT-43704
 	}, " "))
 
-	pctx.StaticVariable("KotlincGlobalFlags", strings.Join([]string{"-language-version 1.9"}, " "))
+	pctx.StaticVariable("KotlincGlobalFlags", strings.Join([]string{}, " "))
 	// Use KotlincKytheGlobalFlags to prevent kotlinc version skew issues between android and
 	// g3 kythe indexers.
 	// This is necessary because there might be instances of kotlin code in android
 	// platform that are not fully compatible with the kotlinc used in g3 kythe indexers.
 	// e.g. uninitialized variables are a warning in 1.*, but an error in 2.*
 	// https://github.com/JetBrains/kotlin/blob/master/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt#L748
-	pctx.StaticVariable("KotlincKytheGlobalFlags", strings.Join([]string{"-language-version 1.9"}, " "))
+	pctx.StaticVariable("KotlincKytheGlobalFlags", strings.Join([]string{}, " "))
 }