[intention-preview] IDEA-304606 Call generatePreview with the copy of file from getElementToMakeWritable, rather than current file

Tested with AddModuleDirectiveFix

GitOrigin-RevId: 769cbab88190cb59bd767d53faf91095a8953ba4

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/AddModuleDirectiveFix.kt

@@ -3,12 +3,10 @@ package com.intellij.codeInsight.daemon.impl.quickfix
 
 import com.intellij.codeInsight.daemon.QuickFixBundle
 import com.intellij.codeInsight.intention.impl.BaseIntentionAction
-import com.intellij.codeInsight.intention.preview.IntentionPreviewInfo
 import com.intellij.codeInspection.LocalQuickFixAndIntentionActionOnPsiElement
 import com.intellij.openapi.editor.Editor
 import com.intellij.openapi.project.Project
 import com.intellij.psi.*
-import com.intellij.psi.util.PsiTreeUtil
 import com.intellij.psi.util.PsiUtil
 
 abstract class AddModuleDirectiveFix(module: PsiJavaModule) : LocalQuickFixAndIntentionActionOnPsiElement(module) {
@@ -21,14 +19,6 @@ abstract class AddModuleDirectiveFix(module: PsiJavaModule) : LocalQuickFixAndIn
     invoke(project, startElement as PsiJavaModule)
 
   protected abstract fun invoke(project: Project, module: PsiJavaModule)
-
-  override fun generatePreview(project: Project, editor: Editor, file: PsiFile): IntentionPreviewInfo {
-    val moduleFile = (startElement.containingFile.copy() as? PsiFile) ?: return IntentionPreviewInfo.EMPTY
-    val module = (PsiTreeUtil.findSameElementInCopy(startElement, moduleFile) as? PsiJavaModule) ?: return IntentionPreviewInfo.EMPTY
-    val beforeText = module.text
-    invoke(project, module)
-    return IntentionPreviewInfo.CustomDiff(moduleFile.fileType, moduleFile.name, beforeText, module.text)
-  }
 }
 
 class AddRequiresDirectiveFix(module: PsiJavaModule, private val requiredName: String) : AddModuleDirectiveFix(module) {

java/java-tests/testSrc/com/intellij/java/codeInspection/Java9ReflectionClassVisibilityTest.kt

@@ -57,7 +57,8 @@ class Java9ReflectionClassVisibilityTest : LightJava9ModulesCodeInsightFixtureTe
   fun testExportsPackagePreview() {
     moduleInfo("module MAIN { requires API; }", MAIN)
     moduleInfo("module API { exports my.api; }", M2)
-    doTestPreview("Add 'exports my.impl' directive to module-info.java", "module API { exports my.api; exports my.impl; }")
+    doTestPreview("Add 'exports my.impl' directive to module-info.java",
+                  "module API { exports my.api;\n    exports my.impl;\n}")
   }
 
   fun testNotInRequirements() {

platform/analysis-api/src/com/intellij/codeInsight/intention/IntentionAction.java

@@ -107,8 +107,10 @@ public interface IntentionAction extends FileModifier {
    * overriding {@code getFileModifierForPreview} or {@code generatePreview} is desired.
    *
    * @param project current project
-   * @param editor editor. Could be a simplified headless Editor implementation that lacks some features.
-   * @param file non-physical file to apply
+   * @param editor editor where a file copy is opened. 
+   *               Could be a simplified headless Editor implementation that lacks some features.
+   * @param file a non-physical file to apply, which is a copy of the file that contains element returned from
+   *             {@link #getElementToMakeWritable(PsiFile)}, or copy of the current file if that method returns null
    * @return an object that describes the action preview to display
    */
   default @NotNull IntentionPreviewInfo generatePreview(@NotNull Project project, @NotNull Editor editor, @NotNull PsiFile file) {

platform/lang-impl/src/com/intellij/codeInsight/intention/impl/preview/IntentionPreviewComputable.kt

@@ -107,11 +107,14 @@ internal class IntentionPreviewComputable(private val project: Project,
         IntentionPreviewInfo.DIFF,
         IntentionPreviewInfo.DIFF_NO_TRIM -> {
           val document = psiFileCopy!!.viewProvider.document
+          val anotherFile = psiFileCopy.originalFile != origFile
           val policy = if (result == IntentionPreviewInfo.DIFF) ComparisonPolicy.TRIM_WHITESPACES else ComparisonPolicy.DEFAULT
           IntentionPreviewDiffResult(
             psiFile = psiFileCopy,
-            origFile = origFile,
+            origFile = psiFileCopy.originalFile,
             policy = policy,
+            fileName = if (anotherFile) psiFileCopy.name else null,
+            normalDiff = !anotherFile,
             lineFragments = comparisonManager.compareLines(origFile.text, document.text, policy, DumbProgressIndicator.INSTANCE))
         }
         IntentionPreviewInfo.EMPTY, IntentionPreviewInfo.FALLBACK_DIFF -> null
@@ -135,21 +138,22 @@ internal class IntentionPreviewComputable(private val project: Project,
 
   private fun invokePreview(origFile: PsiFile, selection: TextRange, caretOffset: Int): Pair<IntentionPreviewInfo, PsiFile?> {
     var info: IntentionPreviewInfo = IntentionPreviewInfo.EMPTY
-    val psiFileCopy = IntentionPreviewUtils.obtainCopyForPreview(origFile)
+    val fileToCopy = action.getElementToMakeWritable(origFile) ?. containingFile ?: origFile
+    val psiFileCopy = IntentionPreviewUtils.obtainCopyForPreview(fileToCopy)
     val editorCopy = IntentionPreviewEditor(psiFileCopy, originalEditor.settings)
-    editorCopy.caretModel.moveToOffset(caretOffset)
-    editorCopy.selectionModel.setSelection(selection.startOffset, selection.endOffset)
+    if (fileToCopy == origFile) {
+      editorCopy.caretModel.moveToOffset(caretOffset)
+      editorCopy.selectionModel.setSelection(selection.startOffset, selection.endOffset)
+    }
     originalEditor.document.setReadOnly(true)
     ProgressManager.checkCanceled()
     IntentionPreviewUtils.previewSession(editorCopy) {
       PostprocessReformattingAspect.getInstance(project)
         .postponeFormattingInside { info = action.generatePreview(project, editorCopy, psiFileCopy) }
     }
-    if (info == IntentionPreviewInfo.FALLBACK_DIFF) {
+    if (info == IntentionPreviewInfo.FALLBACK_DIFF && fileToCopy == origFile) {
       if (!action.startInWriteAction()) return info to null
       if (action.getElementToMakeWritable(originalFile)?.containingFile !== originalFile) return info to null
-      // Use fallback algorithm only if invokeForPreview is not explicitly overridden
-      // in this case, the absence of diff could be intended, thus should not be logged as error
       val action = findCopyIntention(project, editorCopy, psiFileCopy, action) ?: return info to null
       val unwrapped = IntentionActionDelegate.unwrap(action)
       val cls = (if (unwrapped is QuickFixWrapper) unwrapped.fix else unwrapped)::class.java