Use -language-version 1.9 in the kotlinKythe build rule

There are some instances of .kt code in android platform that are not
fully compatible with kotlinc > 2. To account for this version skew when
generating xrefs, implicitly add `-language-version 1.9` to the args in
the .kzip file. The main kotlinc build rules remain the same.

This value has been picked manually by running
`external/kotlinc/bin/kotlinc -version` at ToT

Bug: 265428637
Test: verified that `-language-version 1.9` is added to the build
command of the .kzip files
Test: ran the indexer locally on the .kzip of `PermissionController-lib`
(this android_library contains .kt code that does not compile with
verison >2)

Change-Id: Icfb72800404d83f63204de23a1ec34b40ee05847

1 files changed, 7 insertions, 0 deletions

diff --git a/java/config/kotlin.go b/java/config/kotlin.go
index e5e187cad..302d021db 100644
--- a/java/config/kotlin.go
+++ b/java/config/kotlin.go
@@ -50,4 +50,11 @@ func init() {
 	}, " "))
 
 	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"}, " "))
 }