[LL] Add a test base for PSI-modifying low-level API tests

- To support PSI modification, the test environment requires some
  additional configuration, which is encapsulated in
  `AnalysisApiPsiModificationTestServiceRegistrar`.
- The test also has to allow write access explicitly, which is
  configured in `AnalysisApiFirModifiablePsiSourceTestConfigurator`.

analysis/analysis-api-impl-base/tests/org/jetbrains/kotlin/analysis/api/impl/base/test/configurators/AnalysisApiModifiablePsiTestServiceRegistrar.kt

@@ -0,0 +1,120 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.analysis.api.impl.base.test.configurators
+
+import com.intellij.core.CoreApplicationEnvironment
+import com.intellij.lang.ASTNode
+import com.intellij.mock.MockApplication
+import com.intellij.mock.MockFileDocumentManagerImpl
+import com.intellij.mock.MockProject
+import com.intellij.openapi.editor.Document
+import com.intellij.openapi.editor.impl.DocumentImpl
+import com.intellij.openapi.editor.impl.DocumentWriteAccessGuard
+import com.intellij.openapi.fileEditor.FileDocumentManager
+import com.intellij.openapi.fileEditor.impl.FileDocumentManagerBase
+import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.pom.PomModel
+import com.intellij.pom.core.impl.PomModelImpl
+import com.intellij.pom.tree.TreeAspect
+import com.intellij.psi.PsiFile
+import com.intellij.psi.PsiTreeChangeEvent
+import com.intellij.psi.PsiTreeChangeListener
+import com.intellij.psi.impl.source.codeStyle.IndentHelper
+import org.jetbrains.kotlin.analysis.test.framework.test.configurators.AnalysisApiTestServiceRegistrar
+import org.jetbrains.kotlin.test.services.TestServices
+
+/**
+ * Registers services which are required for PSI modification operations (such as deleting a PSI element) to complete without throwing
+ * exceptions.
+ */
+object AnalysisApiModifiablePsiTestServiceRegistrar : AnalysisApiTestServiceRegistrar() {
+    override fun registerApplicationServices(application: MockApplication, testServices: TestServices) {
+        application.apply {
+            registerFileDocumentManager()
+
+            registerService(IndentHelper::class.java, MockIndentHelper::class.java)
+
+            CoreApplicationEnvironment.registerExtensionPoint(
+                extensionArea,
+                DocumentWriteAccessGuard.EP_NAME,
+                MockDocumentWriteAccessGuard::class.java,
+            )
+        }
+    }
+
+    /**
+     * [MockFileDocumentManagerImpl] doesn't put the cached document as user data under [MockFileDocumentManagerImpl.myCachedDocumentKey] on
+     * the virtual file, making [MockFileDocumentManagerImpl.getCachedDocument] effectively return `null`. We extend the file document
+     * manager to simulate the behavior of [FileDocumentManagerBase], which puts [FileDocumentManagerBase.HARD_REF_TO_DOCUMENT_KEY] user
+     * data on the virtual file.
+     */
+    private fun MockApplication.registerFileDocumentManager() {
+        // To register our own file document manager, we need to remove the manager already registered with our application at this point.
+        picoContainer.unregisterComponent(FileDocumentManager::class.java.name)
+
+        registerService(
+            FileDocumentManager::class.java,
+            object : MockFileDocumentManagerImpl(FileDocumentManagerBase.HARD_REF_TO_DOCUMENT_KEY, { DocumentImpl(it) }) {
+                override fun getDocument(file: VirtualFile): Document? {
+                    val document = super.getDocument(file) ?: return null
+                    file.putUserDataIfAbsent(FileDocumentManagerBase.HARD_REF_TO_DOCUMENT_KEY, document)
+                    return document
+                }
+            },
+        )
+    }
+
+    override fun registerProjectExtensionPoints(project: MockProject, testServices: TestServices) {
+        CoreApplicationEnvironment.registerExtensionPoint(
+            project.extensionArea,
+            PsiTreeChangeListener.EP.name,
+            MockPsiTreeChangeListener::class.java,
+        )
+    }
+
+    override fun registerProjectServices(project: MockProject, testServices: TestServices) {
+        project.apply {
+            registerService(TreeAspect::class.java)
+            registerService(PomModel::class.java, PomModelImpl::class.java)
+        }
+    }
+}
+
+@Suppress("UnstableApiUsage")
+private class MockDocumentWriteAccessGuard : DocumentWriteAccessGuard() {
+    override fun isWritable(document: Document): Result = success()
+}
+
+private class MockIndentHelper : IndentHelper() {
+    override fun getIndent(file: PsiFile, element: ASTNode): Int = 0
+    override fun getIndent(file: PsiFile, element: ASTNode, includeNonSpace: Boolean): Int = 0
+}
+
+private class MockPsiTreeChangeListener : PsiTreeChangeListener {
+    override fun beforeChildAddition(event: PsiTreeChangeEvent) {}
+
+    override fun beforeChildRemoval(event: PsiTreeChangeEvent) {}
+
+    override fun beforeChildReplacement(event: PsiTreeChangeEvent) {}
+
+    override fun beforeChildMovement(event: PsiTreeChangeEvent) {}
+
+    override fun beforeChildrenChange(event: PsiTreeChangeEvent) {}
+
+    override fun beforePropertyChange(event: PsiTreeChangeEvent) {}
+
+    override fun childAdded(event: PsiTreeChangeEvent) {}
+
+    override fun childRemoved(event: PsiTreeChangeEvent) {}
+
+    override fun childReplaced(event: PsiTreeChangeEvent) {}
+
+    override fun childrenChanged(event: PsiTreeChangeEvent) {}
+
+    override fun childMoved(event: PsiTreeChangeEvent) {}
+
+    override fun propertyChanged(event: PsiTreeChangeEvent) {}
+}

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/test/base/AbstractLowLevelApiModifiablePsiSingleFileTest.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.analysis.low.level.api.fir.test.base
+
+import com.intellij.openapi.application.ApplicationManager
+import com.intellij.openapi.command.WriteCommandAction
+import org.jetbrains.kotlin.analysis.api.impl.base.test.configurators.AnalysisApiModifiablePsiTestServiceRegistrar
+import org.jetbrains.kotlin.analysis.low.level.api.fir.test.configurators.AnalysisApiFirSourceTestConfigurator
+import org.jetbrains.kotlin.analysis.test.framework.test.configurators.AnalysisApiTestConfigurator
+import org.jetbrains.kotlin.analysis.test.framework.test.configurators.AnalysisApiTestServiceRegistrar
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.test.services.TestModuleStructure
+import org.jetbrains.kotlin.test.services.TestServices
+import org.jetbrains.kotlin.test.testFramework.runWriteAction
+
+/**
+ * [AbstractLowLevelApiModifiablePsiSingleFileTest] applies additional configuration to support the modification of PSI during the test.
+ */
+abstract class AbstractLowLevelApiModifiablePsiSingleFileTest : AbstractLowLevelApiSingleFileTest() {
+    override val configurator: AnalysisApiTestConfigurator get() = AnalysisApiFirModifiablePsiSourceTestConfigurator
+
+    abstract fun doTestWithPsiModification(ktFile: KtFile, moduleStructure: TestModuleStructure, testServices: TestServices)
+
+    final override fun doTestByFileStructure(ktFile: KtFile, moduleStructure: TestModuleStructure, testServices: TestServices) {
+        ApplicationManager.getApplication().invokeAndWait {
+            runWriteAction {
+                WriteCommandAction.runWriteCommandAction(ktFile.project) {
+                    doTestWithPsiModification(ktFile, moduleStructure, testServices)
+                }
+            }
+        }
+    }
+}
+
+object AnalysisApiFirModifiablePsiSourceTestConfigurator : AnalysisApiFirSourceTestConfigurator(analyseInDependentSession = false) {
+    override val serviceRegistrars: List<AnalysisApiTestServiceRegistrar> = buildList {
+        addAll(super.serviceRegistrars)
+        add(AnalysisApiModifiablePsiTestServiceRegistrar)
+    }
+
+    override val isWriteAccessAllowed: Boolean get() = true
+}