correct event firing when AST has no PSI (EA-111703 - IAE: PsiChangeHandler.$$$reportNull$$$)

platform/core-impl/src/com/intellij/pom/tree/events/impl/ChangeInfoImpl.java

@@ -22,6 +22,7 @@ import com.intellij.psi.impl.PsiManagerImpl;
 import com.intellij.psi.impl.PsiTreeChangeEventImpl;
 import com.intellij.psi.impl.source.tree.CompositeElement;
 import com.intellij.psi.impl.source.tree.TreeElement;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public class ChangeInfoImpl implements ChangeInfo {
@@ -64,12 +65,10 @@ public class ChangeInfoImpl implements ChangeInfo {
   }
 
   void fireEvent(int parentStart, PsiFile file, CompositeElement parent) {
-    PsiTreeChangeEventImpl e = new PsiTreeChangeEventImpl(file.getManager());
-    e.setFile(file);
-    e.setOffset(myOffset + parentStart);
+    PsiTreeChangeEventImpl e = createEvent(file, myOffset + parentStart);
 
     if (myOldChild == myNewChild && myNewChild != null) {
-      childrenChanged(e, myNewChild);
+      childrenChanged(e, myNewChild, myOldLength);
     }
     else if (myOldChild != null && myNewChild != null) {
       childReplaced(e, myOldChild, myNewChild, parent);
@@ -82,6 +81,19 @@ public class ChangeInfoImpl implements ChangeInfo {
     }
   }
 
+  @NotNull
+  static PsiTreeChangeEventImpl createEvent(PsiFile file, int offset) {
+    PsiTreeChangeEventImpl e = new PsiTreeChangeEventImpl(file.getManager());
+    e.setFile(file);
+    e.setOffset(offset);
+    return e;
+  }
+
+  boolean hasNoPsi() {
+    return myOldChild != null && myOldChild.getPsi() == null || 
+           myNewChild != null && myNewChild.getPsi() == null;
+  }
+
   private static void childAdded(PsiTreeChangeEventImpl e, TreeElement child, CompositeElement parent) {
     e.setParent(parent.getPsi());
     e.setChild(child.getPsi());
@@ -104,9 +116,9 @@ public class ChangeInfoImpl implements ChangeInfo {
     getPsiManagerImpl(e).childReplaced(e);
   }
 
-  private void childrenChanged(PsiTreeChangeEventImpl e, TreeElement parent) {
+  static void childrenChanged(PsiTreeChangeEventImpl e, TreeElement parent, int oldLength) {
     e.setParent(parent.getPsi());
-    e.setOldLength(myOldLength);
+    e.setOldLength(oldLength);
     getPsiManagerImpl(e).childrenChanged(e);
   }
 

platform/core-impl/src/com/intellij/pom/tree/events/impl/TreeChangeImpl.java

@@ -39,6 +39,7 @@ public class TreeChangeImpl implements TreeChange, Comparable<TreeChangeImpl> {
 
   public TreeChangeImpl(@NotNull CompositeElement parent) {
     myParent = parent;
+    assert myParent.getPsi() != null;
     mySuperParents = JBIterable.generate(parent.getTreeParent(), TreeElement::getTreeParent).toList();
     for (TreeElement child : getCurrentChildren()) {
       myInitialChildren.add(child);
@@ -152,7 +153,13 @@ public class TreeChangeImpl implements TreeChange, Comparable<TreeChangeImpl> {
 
   void fireEvents(PsiFile file) {
     int start = myParent.getStartOffset();
-    for (ChangeInfoImpl change : getAllChanges().values()) {
+    Collection<ChangeInfoImpl> changes = getAllChanges().values();
+    if (ContainerUtil.exists(changes, c -> c.hasNoPsi())) {
+      ChangeInfoImpl.childrenChanged(ChangeInfoImpl.createEvent(file, start), myParent, myParent.getTextLength() - getLengthDelta());
+      return;
+    }
+    
+    for (ChangeInfoImpl change : changes) {
       change.fireEvent(start, file, myParent);
     }
   }

platform/platform-tests/testSrc/com/intellij/psi/impl/PsiEventConsistencyTest.kt

@@ -125,6 +125,17 @@ class PsiEventConsistencyTest : LightPlatformCodeInsightFixtureTestCase() {
       assertEquals(root.text, file.viewProvider.document!!.text)
     }
   }
+  
+  fun `test changes on AST without PSI`() {
+    val file = createEmptyFile()
+    WriteCommandAction.runWriteCommandAction(project) {
+      val root = file.node as FileElement
+      root.replaceChild(root.firstChildNode, leaf(leafTypes[0], "A"))
+      
+      assertEquals("A", root.text)
+      assertEquals(root.text, file.viewProvider.document!!.text)
+    }
+  }
 
   fun testPsiDocSynchronization() {
     ImperativeCommand.checkScenarios { RandomAstChanges() }
@@ -198,6 +209,13 @@ class PsiEventConsistencyTest : LightPlatformCodeInsightFixtureTestCase() {
   }
 
   private fun leaf(type: IElementType, text: String): TreeElement {
+    if (text[0].isUpperCase()) {
+      // no PSI
+      return withDummyHolder(object : LeafElement(type, text) {
+        override fun toString() = text
+      })
+    }
+
     return withDummyHolder(object : LeafPsiElement(type, text) {
       override fun toString() = text
     })