KSP is not thread safe in a multiplex worker environment #1385
Description
When using KSP in a persistent multiplexed worker environment we see unexplainable build errors claiming that KSP is unable to resolve types defined in the same module that's currently being processed. We believe this is happening because of the changed introduced here to avoid leaking memory, are now causing KSP to wipe out the resolver cached needed by other threads.
A few examples of the errors that we are seeing:
KSTypeReference#resolve returning null:
error: [ksp] java.lang.NullPointerException
at com.google.devtools.ksp.symbol.impl.kotlin.KSTypeReferenceImpl.resolve(KSTypeReferenceImpl.kt:124)
at com.lyft.ksp.skabbard.KspUtilsKt.resolveToUnderlying(KspUtils.kt:61)
at com.lyft.ksp.skabbard.ClassOnlyTraversingResolver$getSymbolsWithAnnotation$1.invoke(ClassOnlyTraversingResolver.kt:37)
at com.lyft.ksp.skabbard.ClassOnlyTraversingResolver$getSymbolsWithAnnotation$1.invoke(ClassOnlyTraversingResolver.kt:33)
at kotlin.sequences.FilteringSequence$iterator$1.calcNext(Sequences.kt:171)
at kotlin.sequences.FilteringSequence$iterator$1.hasNext(Sequences.kt:194)
at kotlin.sequences.FilteringSequence$iterator$1.calcNext(Sequences.kt:169)
at kotlin.sequences.FilteringSequence$iterator$1.hasNext(Sequences.kt:194)
at kotlin.sequences.TransformingSequence$iterator$1.hasNext(Sequences.kt:214)
KSP is unable to resolve types defined in the same module that's being processed:
error: [ksp] java.lang.IllegalStateException: Cannot find package fragment com.lyft.android.scoop.unidirectional.interop
vFile = /private/var/tmp/_bazel_blee/499a001013731d09bffd82f8601a3161/execroot/instantandroid/instant-scoop/unidirectional/interop/src/main/java/com/lyft/android/scoop/unidirectional/interop/ScoopInteropGraph.kt, file package = 'com.lyft.android.scoop.unidirectional.interop'
at org.jetbrains.kotlin.resolve.lazy.declarations.AbstractDeclarationProviderFactory.diagnoseMissingPackageFragment(AbstractDeclarationProviderFactory.java:51)
at org.jetbrains.kotlin.resolve.lazy.ResolveSession.getPackageFragmentOrDiagnoseFailure(ResolveSession.java:275)
at org.jetbrains.kotlin.resolve.lazy.LazyDeclarationResolver.getMemberScopeDeclaredIn$frontend(LazyDeclarationResolver.kt:223)
at org.jetbrains.kotlin.resolve.lazy.LazyDeclarationResolver.findClassDescriptorIfAny(LazyDeclarationResolver.kt:71)
at org.jetbrains.kotlin.resolve.lazy.LazyDeclarationResolver.getClassDescriptorIfAny(LazyDeclarationResolver.kt:59)
at org.jetbrains.kotlin.resolve.lazy.LazyDeclarationResolver$resolveToDescriptor$1.visitClass(LazyDeclarationResolver.kt:100)
at org.jetbrains.kotlin.resolve.lazy.LazyDeclarationResolver$resolveToDescriptor$1.visitClass(LazyDeclarationResolver.kt:94)