FIR IDE: implement completion for packages

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirCompletionContributor.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.idea.fir.low.level.api.util.originalKtFile
 import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtFile
+import java.io.File
 
 class KotlinFirCompletionContributor : CompletionContributor() {
     init {
@@ -98,6 +99,10 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
                 complete(importDirectivePackageMembersCompletionContributor, positionContext)
             }
 
+            is FirPackageDirectivePositionContext -> {
+                complete(packageCompletionContributor, positionContext)
+            }
+
             is FirUnknownPositionContext -> {
                 complete(keywordContributor, positionContext)
             }

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/context/FirPositionCompletionContext.kt

@@ -30,9 +30,16 @@ internal class FirImportDirectivePositionContext(
     override val reference: KtSimpleNameReference,
     override val nameExpression: KtSimpleNameExpression,
     override val explicitReceiver: KtExpression?,
-    val importDirective: KtImportDirective,
 ) : FirNameReferencePositionContext()
 
+internal class FirPackageDirectivePositionContext(
+    override val position: PsiElement,
+    override val reference: KtSimpleNameReference,
+    override val nameExpression: KtSimpleNameExpression,
+    override val explicitReceiver: KtExpression?,
+) : FirNameReferencePositionContext()
+
+
 
 internal class FirTypeNameReferencePositionContext(
     override val position: PsiElement,
@@ -90,7 +97,15 @@ internal object FirPositionCompletionContextDetector {
                     reference,
                     nameExpression,
                     explicitReceiver,
-                    parent.parentOfType(withSelf = true)!!
+                )
+            }
+
+            nameExpression.isImportExpressionInsidePackageDirective() -> {
+                FirPackageDirectivePositionContext(
+                    position,
+                    reference,
+                    nameExpression,
+                    explicitReceiver,
                 )
             }
             else -> {
@@ -108,6 +123,15 @@ internal object FirPositionCompletionContextDetector {
         else -> false
     }
 
+    private fun KtExpression.isImportExpressionInsidePackageDirective() = when (val parent = parent) {
+        is KtPackageDirective -> parent.packageNameExpression == this
+        is KtDotQualifiedExpression -> {
+            val packageDirective = parent.parent as? KtPackageDirective
+            packageDirective?.packageNameExpression == parent
+        }
+        else -> false
+    }
+
     private fun detectForTypeContext(
         userType: KtUserType,
         position: PsiElement,
@@ -145,7 +169,7 @@ internal object FirPositionCompletionContextDetector {
                 positionContext.nameExpression,
                 action
             )
-            is FirUnknownPositionContext, is FirImportDirectivePositionContext -> {
+            is FirUnknownPositionContext, is FirImportDirectivePositionContext, is FirPackageDirectivePositionContext -> {
                 analyse(basicContext.originalKtFile, action)
             }
         }