Introduce LT file abstraction in tests parallel to KtFile

allows to create a valid LT-based file with synthetic path important
for dumps comparisons in tests

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/analysis/FirAnalyzerFacade.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.fir.builder.PsiHandlingMode
 import org.jetbrains.kotlin.fir.builder.RawFirBuilder
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.lightTree.LightTree2Fir
+import org.jetbrains.kotlin.fir.lightTree.LightTreeFile
 import org.jetbrains.kotlin.fir.moduleData
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.providers.firProvider
@@ -30,7 +31,6 @@ import org.jetbrains.kotlin.ir.backend.jvm.serialization.JvmDescriptorMangler
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImpl
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi2ir.generators.GeneratorExtensions
-import java.io.File
 
 abstract class AbstractFirAnalyzerFacade {
     abstract val scopeSession: ScopeSession
@@ -45,7 +45,7 @@ class FirAnalyzerFacade(
     val session: FirSession,
     val languageVersionSettings: LanguageVersionSettings,
     val ktFiles: Collection<KtFile> = emptyList(), // may be empty if light tree mode enabled
-    val originalFiles: Collection<File> = emptyList(), // may be empty if light tree mode disabled
+    val lightTreeFiles: Collection<LightTreeFile> = emptyList(), // may be empty if light tree mode disabled
     val irGeneratorExtensions: Collection<IrGenerationExtension>,
     val useLightTree: Boolean = false,
     val enablePluginPhases: Boolean = false,
@@ -62,7 +62,7 @@ class FirAnalyzerFacade(
         val firProvider = (session.firProvider as FirProviderImpl)
         firFiles = if (useLightTree) {
             val builder = LightTree2Fir(session, firProvider.kotlinScopeProvider)
-            originalFiles.map {
+            lightTreeFiles.map {
                 builder.buildFirFile(it).also { firFile ->
                     firProvider.recordFile(firFile)
                 }

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/LightTree2Fir.kt

@@ -39,6 +39,12 @@ class LightTree2Fir(
             KotlinLightParser.parseLambdaExpression(builder)
             return builder.lightTree
         }
+
+        fun buildLightTree(code: String): FlyweightCapableTreeStructure<LighterASTNode> {
+            val builder = PsiBuilderFactoryImpl().createBuilder(parserDefinition, makeLexer(), code)
+            KotlinLightParser.parse(builder)
+            return builder.lightTree
+        }
     }
 
     fun buildFirFile(path: Path): FirFile {
@@ -50,10 +56,11 @@ class LightTree2Fir(
         return buildFirFile(code, file.name, file.path)
     }
 
-    fun buildLightTree(code: String): FlyweightCapableTreeStructure<LighterASTNode> {
-        val builder = PsiBuilderFactoryImpl().createBuilder(parserDefinition, makeLexer(), code)
-        KotlinLightParser.parse(builder)
-        return builder.lightTree
+    fun buildFirFile(lightTreeFile: LightTreeFile): FirFile = with(lightTreeFile) {
+        DeclarationsConverter(
+            session, scopeProvider, lightTree, diagnosticsReporter = diagnosticsReporter,
+            diagnosticContext = makeDiagnosticContext(path)
+        ).convertFile(lightTree.root, fileName, path)
     }
 
     fun buildFirFile(code: String, fileName: String, path: String?): FirFile {
@@ -63,3 +70,10 @@ class LightTree2Fir(
             .convertFile(lightTree.root, fileName, path)
     }
 }
+
+data class LightTreeFile(
+    val lightTree: FlyweightCapableTreeStructure<LighterASTNode>,
+    val fileName: String,
+    val path: String?
+)
+

compiler/fir/raw-fir/light-tree2fir/tests/org/jetbrains/kotlin/fir/lightTree/TotalKotlinTest.kt

@@ -35,7 +35,7 @@ class TotalKotlinTest : AbstractRawFirBuilderTestCase() {
 
     private fun generateFirFromLightTree(onlyLightTree: Boolean, converter: LightTree2Fir, text: String, fileName: String, filePath: String) {
         if (onlyLightTree) {
-            val lightTree = converter.buildLightTree(text)
+            val lightTree = LightTree2Fir.buildLightTree(text)
             DebugUtil.lightTreeToString(lightTree, false)
         } else {
             val firFile = converter.buildFirFile(text, fileName, filePath)

compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/services/SourceFileProvider.kt

@@ -6,6 +6,8 @@
 package org.jetbrains.kotlin.test.services
 
 import com.intellij.openapi.project.Project
+import org.jetbrains.kotlin.fir.lightTree.LightTree2Fir
+import org.jetbrains.kotlin.fir.lightTree.LightTreeFile
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.test.model.TestFile
 import org.jetbrains.kotlin.test.util.KtTestUtil
@@ -97,6 +99,20 @@ fun SourceFileProvider.getKtFilesForSourceFiles(testFiles: Collection<TestFile>,
     }.toMap()
 }
 
+fun SourceFileProvider.getLightTreeKtFileForSourceFile(testFile: TestFile): LightTreeFile {
+    val shortName = testFile.name.substringAfterLast('/').substringAfterLast('\\')
+    val file = getRealFileForSourceFile(testFile)
+    val lightTree = LightTree2Fir.buildLightTree(file.readText())
+    return LightTreeFile(lightTree, shortName, "/$shortName") // emulating behavior of KtTestUtil.createFile so path looks the same in testdata
+}
+
+fun SourceFileProvider.getLightTreeFilesForSourceFiles(testFiles: Collection<TestFile>): Map<TestFile, LightTreeFile> {
+    return testFiles.mapNotNull {
+        if (!it.isKtFile) return@mapNotNull null
+        it to getLightTreeKtFileForSourceFile(it)
+    }.toMap()
+}
+
 val TestFile.isKtFile: Boolean
     get() = name.endsWith(".kt") || name.endsWith(".kts")
 

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/FirFrontendFacade.kt

@@ -66,8 +66,8 @@ class FirFrontendFacade(
         PsiElementFinder.EP.getPoint(project).unregisterExtension(JavaElementFinder::class.java)
 
         val lightTreeEnabled = FirDiagnosticsDirectives.USE_LIGHT_TREE in module.directives
-        val (ktFiles, originalFiles) = if (lightTreeEnabled) {
-            emptyList<KtFile>() to module.files.filter { it.isKtFile }.map { testServices.sourceFileProvider.getRealFileForSourceFile(it) }
+        val (ktFiles, lightTreeFiles) = if (lightTreeEnabled) {
+            emptyList<KtFile>() to testServices.sourceFileProvider.getLightTreeFilesForSourceFiles(module.files).values
         } else {
             testServices.sourceFileProvider.getKtFilesForSourceFiles(module.files, project).values to emptyList()
         }
@@ -120,7 +120,7 @@ class FirFrontendFacade(
             session,
             languageVersionSettings,
             ktFiles,
-            originalFiles,
+            lightTreeFiles,
             IrGenerationExtension.getInstances(project),
             lightTreeEnabled,
             enablePluginPhases