From 6fe6119f89b66234c385d653f58a46e4bb7bdccd Mon Sep 17 00:00:00 2001
From: Kuba Niegowski <j.niegowski@cksource.com>
Date: Wed, 12 Apr 2023 19:22:05 +0200
Subject: [PATCH] The target ranges should not be fixed while editor is in
 composition mode.

---
 .../src/controller/editingcontroller.ts       | 11 ++++++++--
 .../tests/controller/editingcontroller.js     | 22 +++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/packages/ckeditor5-engine/src/controller/editingcontroller.ts b/packages/ckeditor5-engine/src/controller/editingcontroller.ts
index 28343c619dd..1a7d6ab2082 100644
--- a/packages/ckeditor5-engine/src/controller/editingcontroller.ts
+++ b/packages/ckeditor5-engine/src/controller/editingcontroller.ts
@@ -10,6 +10,7 @@
 import {
 	CKEditorError,
 	ObservableMixin,
+	env,
 	type GetCallback
 } from '@ckeditor/ckeditor5-utils';
 
@@ -125,7 +126,7 @@ export default class EditingController extends ObservableMixin() {
 
 		// Fix `beforeinput` target ranges so that they map to the valid model ranges.
 		this.listenTo<ViewDocumentInputEvent>( this.view.document, 'beforeinput',
-			fixTargetRanges( this.mapper, this.model.schema ),
+			fixTargetRanges( this.mapper, this.model.schema, this.view ),
 			{ priority: 'high' }
 		);
 
@@ -252,8 +253,14 @@ export default class EditingController extends ObservableMixin() {
  *
  * This is using the same logic as the selection post-fixer.
  */
-function fixTargetRanges( mapper: Mapper, schema: Schema ): GetCallback<ViewDocumentInputEvent> {
+function fixTargetRanges( mapper: Mapper, schema: Schema, view: View ): GetCallback<ViewDocumentInputEvent> {
 	return ( evt, data ) => {
+		// The Renderer is disabled while composing on non-android browsers, so we can't be sure that target ranges
+		// could be properly mapped to view and model because the DOM and view tree drifted apart.
+		if ( view.document.isComposing && !env.isAndroid ) {
+			return;
+		}
+
 		for ( let i = 0; i < data.targetRanges.length; i++ ) {
 			const viewRange = data.targetRanges[ i ];
 			const modelRange = mapper.toModelRange( viewRange );
diff --git a/packages/ckeditor5-engine/tests/controller/editingcontroller.js b/packages/ckeditor5-engine/tests/controller/editingcontroller.js
index 657c8832186..6aea8fdb966 100644
--- a/packages/ckeditor5-engine/tests/controller/editingcontroller.js
+++ b/packages/ckeditor5-engine/tests/controller/editingcontroller.js
@@ -935,6 +935,28 @@ describe( 'EditingController', () => {
 			sinon.assert.calledOnce( enterSpy );
 		} );
 
+		it( 'should not crash while trying to fix null range while composing', () => {
+			setModelData( model, '<paragraph>a</paragraph>' );
+
+			const targetRanges = [ null ];
+
+			const eventData = {
+				inputType: 'insertCompositionText',
+				data: 'ab',
+				targetRanges
+			};
+
+			viewDocument.isComposing = true;
+			fireBeforeInputEvent( eventData );
+
+			// Verify beforeinput range.
+			sinon.assert.calledOnce( beforeInputSpy );
+
+			const inputData = beforeInputSpy.args[ 0 ][ 1 ];
+			expect( inputData.inputType ).to.equal( eventData.inputType );
+			expect( inputData.targetRanges[ 0 ] ).to.be.null;
+		} );
+
 		function fireBeforeInputEvent( eventData ) {
 			viewDocument.fire( 'beforeinput', {
 				domEvent: {