updateEditingValueWithDeltas should fail loudly when TextRange is invalid (#107426)

* Make deltas fail loudly

* analyzer fixes

* empty

* updates

* Analyzer fixes

* Make it more obvious what kind of TextRange is failing and where

* update tests

* Add tests for concrete TextEditinDelta apply method

* trailing spaces

* address nits

* fix analyzer
Co-authored-by: Renzo Olivares <roliv@google.com>

packages/flutter/lib/src/services/text_editing_delta.dart

@@ -24,13 +24,21 @@ TextAffinity? _toTextAffinity(String? affinity) {
   return null;
 }
 
-/// Replaces a range of text in the original string with the text given in the
-/// replacement string.
-String _replace(String originalText, String replacementText, int start, int end) {
-  final String textStart = originalText.substring(0, start);
-  final String textEnd = originalText.substring(end, originalText.length);
-  final String newText = textStart + replacementText + textEnd;
-  return newText;
+// Replaces a range of text in the original string with the text given in the
+// replacement string.
+String _replace(String originalText, String replacementText, TextRange replacementRange) {
+  assert(replacementRange.isValid);
+  return originalText.replaceRange(replacementRange.start, replacementRange.end, replacementText);
+}
+
+// Verify that the given range is within the text.
+bool _debugTextRangeIsValid(TextRange range, String text) {
+  if (!range.isValid) {
+    return true;
+  }
+
+  return (range.start >= 0 && range.start <= text.length)
+                            && (range.end >= 0 && range.end <= text.length);
 }
 
 /// A structure representing a granular change that has occurred to the editing
@@ -126,6 +134,9 @@ abstract class TextEditingDelta {
     );
 
     if (isNonTextUpdate) {
+      assert(_debugTextRangeIsValid(newSelection, oldText), 'The selection range: $newSelection is not within the bounds of text: $oldText of length: ${oldText.length}');
+      assert(_debugTextRangeIsValid(newComposing, oldText), 'The composing range: $newComposing is not within the bounds of text: $oldText of length: ${oldText.length}');
+
       return TextEditingDeltaNonTextUpdate(
         oldText: oldText,
         selection: newSelection,
@@ -133,7 +144,13 @@ abstract class TextEditingDelta {
       );
     }
 
-    final String newText = _replace(oldText, replacementSource, replacementDestinationStart, replacementDestinationEnd);
+    assert(_debugTextRangeIsValid(TextRange(start: replacementDestinationStart, end: replacementDestinationEnd), oldText), 'The delta range: ${TextRange(start: replacementSourceStart, end: replacementSourceEnd)} is not within the bounds of text: $oldText of length: ${oldText.length}');
+
+    final String newText = _replace(oldText, replacementSource, TextRange(start: replacementDestinationStart, end: replacementDestinationEnd));
+
+    assert(_debugTextRangeIsValid(newSelection, newText), 'The selection range: $newSelection is not within the bounds of text: $newText of length: ${newText.length}');
+    assert(_debugTextRangeIsValid(newComposing, newText), 'The composing range: $newComposing is not within the bounds of text: $newText of length: ${newText.length}');
+
     final bool isEqual = oldText == newText;
 
     final bool isDeletionGreaterThanOne = (replacementDestinationEnd - replacementDestinationStart) - (replacementSourceEnd - replacementSourceStart) > 1;
@@ -265,7 +282,10 @@ class TextEditingDeltaInsertion extends TextEditingDelta {
     // policy and apply the delta to the oldText. This is due to the asyncronous
     // nature of the connection between the framework and platform text input plugins.
     String newText = oldText;
-    newText = _replace(newText, textInserted, insertionOffset, insertionOffset);
+    assert(_debugTextRangeIsValid(TextRange.collapsed(insertionOffset), newText), 'Applying TextEditingDeltaInsertion failed, the insertionOffset: $insertionOffset is not within the bounds of $newText of length: ${newText.length}');
+    newText = _replace(newText, textInserted, TextRange.collapsed(insertionOffset));
+    assert(_debugTextRangeIsValid(selection, newText), 'Applying TextEditingDeltaInsertion failed, the selection range: $selection is not within the bounds of $newText of length: ${newText.length}');
+    assert(_debugTextRangeIsValid(composing, newText), 'Applying TextEditingDeltaInsertion failed, the composing range: $composing is not within the bounds of $newText of length: ${newText.length}');
     return value.copyWith(text: newText, selection: selection, composing: composing);
   }
 }
@@ -298,7 +318,10 @@ class TextEditingDeltaDeletion extends TextEditingDelta {
     // policy and apply the delta to the oldText. This is due to the asyncronous
     // nature of the connection between the framework and platform text input plugins.
     String newText = oldText;
-    newText = _replace(newText, '', deletedRange.start, deletedRange.end);
+    assert(_debugTextRangeIsValid(deletedRange, newText), 'Applying TextEditingDeltaDeletion failed, the deletedRange: $deletedRange is not within the bounds of $newText of length: ${newText.length}');
+    newText = _replace(newText, '', deletedRange);
+    assert(_debugTextRangeIsValid(selection, newText), 'Applying TextEditingDeltaDeletion failed, the selection range: $selection is not within the bounds of $newText of length: ${newText.length}');
+    assert(_debugTextRangeIsValid(composing, newText), 'Applying TextEditingDeltaDeletion failed, the composing range: $composing is not within the bounds of $newText of length: ${newText.length}');
     return value.copyWith(text: newText, selection: selection, composing: composing);
   }
 }
@@ -341,7 +364,10 @@ class TextEditingDeltaReplacement extends TextEditingDelta {
     // policy and apply the delta to the oldText. This is due to the asyncronous
     // nature of the connection between the framework and platform text input plugins.
     String newText = oldText;
-    newText = _replace(newText, replacementText, replacedRange.start, replacedRange.end);
+    assert(_debugTextRangeIsValid(replacedRange, newText), 'Applying TextEditingDeltaReplacement failed, the replacedRange: $replacedRange is not within the bounds of $newText of length: ${newText.length}');
+    newText = _replace(newText, replacementText, replacedRange);
+    assert(_debugTextRangeIsValid(selection, newText), 'Applying TextEditingDeltaReplacement failed, the selection range: $selection is not within the bounds of $newText of length: ${newText.length}');
+    assert(_debugTextRangeIsValid(composing, newText), 'Applying TextEditingDeltaReplacement failed, the composing range: $composing is not within the bounds of $newText of length: ${newText.length}');
     return value.copyWith(text: newText, selection: selection, composing: composing);
   }
 }
@@ -372,6 +398,8 @@ class TextEditingDeltaNonTextUpdate extends TextEditingDelta {
     // To stay inline with the plain text model we should follow a last write wins
     // policy and apply the delta to the oldText. This is due to the asyncronous
     // nature of the connection between the framework and platform text input plugins.
+    assert(_debugTextRangeIsValid(selection, oldText), 'Applying TextEditingDeltaNonTextUpdate failed, the selection range: $selection is not within the bounds of $oldText of length: ${oldText.length}');
+    assert(_debugTextRangeIsValid(composing, oldText), 'Applying TextEditingDeltaNonTextUpdate failed, the composing region: $composing is not within the bounds of $oldText of length: ${oldText.length}');
     return TextEditingValue(text: oldText, selection: selection, composing: composing);
   }
 }

packages/flutter/test/services/delta_text_input_test.dart

@@ -4,6 +4,7 @@
 
 import 'dart:convert' show jsonDecode;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -65,6 +66,162 @@ void main() {
         expect(client.latestMethodCall, 'updateEditingValueWithDeltas');
       },
     );
+
+    test('Invalid TextRange fails loudly when being converted to JSON - NonTextUpdate', () async {
+      final List<FlutterErrorDetails> record = <FlutterErrorDetails>[];
+      FlutterError.onError = (FlutterErrorDetails details) {
+        record.add(details);
+      };
+
+      final FakeDeltaTextInputClient client = FakeDeltaTextInputClient(const TextEditingValue(text: '1'));
+      const TextInputConfiguration configuration = TextInputConfiguration(enableDeltaModel: true);
+      TextInput.attach(client, configuration);
+
+      const String jsonDelta = '{'
+          '"oldText": "1",'
+          ' "deltaText": "",'
+          ' "deltaStart": -1,'
+          ' "deltaEnd": -1,'
+          ' "selectionBase": 3,'
+          ' "selectionExtent": 3,'
+          ' "selectionAffinity" : "TextAffinity.downstream" ,'
+          ' "selectionIsDirectional": false,'
+          ' "composingBase": -1,'
+          ' "composingExtent": -1}';
+
+      final ByteData? messageBytes = const JSONMessageCodec().encodeMessage(<String, dynamic>{
+        'method': 'TextInputClient.updateEditingStateWithDeltas',
+        'args': <dynamic>[-1, jsonDecode('{"deltas": [$jsonDelta]}')],
+      });
+
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+        'flutter/textinput',
+        messageBytes,
+        (ByteData? _) {},
+      );
+      expect(record.length, 1);
+      // Verify the error message in parts because Web formats the message
+      // differently from others.
+      expect(record[0].exception.toString(), matches(RegExp(r'\bThe selection range: TextSelection.collapsed\(offset: 3, affinity: TextAffinity.downstream, isDirectional: false\)(?!\w)')));
+      expect(record[0].exception.toString(), matches(RegExp(r'\bis not within the bounds of text: 1 of length: 1\b')));
+    });
+
+    test('Invalid TextRange fails loudly when being converted to JSON - Faulty deltaStart and deltaEnd', () async {
+      final List<FlutterErrorDetails> record = <FlutterErrorDetails>[];
+      FlutterError.onError = (FlutterErrorDetails details) {
+        record.add(details);
+      };
+
+      final FakeDeltaTextInputClient client = FakeDeltaTextInputClient(TextEditingValue.empty);
+      const TextInputConfiguration configuration = TextInputConfiguration(enableDeltaModel: true);
+      TextInput.attach(client, configuration);
+
+      const String jsonDelta = '{'
+          '"oldText": "",'
+          ' "deltaText": "hello",'
+          ' "deltaStart": 0,'
+          ' "deltaEnd": 1,'
+          ' "selectionBase": 5,'
+          ' "selectionExtent": 5,'
+          ' "selectionAffinity" : "TextAffinity.downstream" ,'
+          ' "selectionIsDirectional": false,'
+          ' "composingBase": -1,'
+          ' "composingExtent": -1}';
+
+      final ByteData? messageBytes = const JSONMessageCodec().encodeMessage(<String, dynamic>{
+        'method': 'TextInputClient.updateEditingStateWithDeltas',
+        'args': <dynamic>[-1, jsonDecode('{"deltas": [$jsonDelta]}')],
+      });
+
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+        'flutter/textinput',
+        messageBytes,
+        (ByteData? _) {},
+      );
+      expect(record.length, 1);
+      // Verify the error message in parts because Web formats the message
+      // differently from others.
+      expect(record[0].exception.toString(), matches(RegExp(r'\bThe delta range: TextRange\(start: 0, end: 5\)(?!\w)')));
+      expect(record[0].exception.toString(), matches(RegExp(r'\bis not within the bounds of text:  of length: 0\b')));
+    });
+
+    test('Invalid TextRange fails loudly when being converted to JSON - Faulty Selection', () async {
+      final List<FlutterErrorDetails> record = <FlutterErrorDetails>[];
+      FlutterError.onError = (FlutterErrorDetails details) {
+        record.add(details);
+      };
+
+      final FakeDeltaTextInputClient client = FakeDeltaTextInputClient(TextEditingValue.empty);
+      const TextInputConfiguration configuration = TextInputConfiguration(enableDeltaModel: true);
+      TextInput.attach(client, configuration);
+
+      const String jsonDelta = '{'
+          '"oldText": "",'
+          ' "deltaText": "hello",'
+          ' "deltaStart": 0,'
+          ' "deltaEnd": 0,'
+          ' "selectionBase": 6,'
+          ' "selectionExtent": 6,'
+          ' "selectionAffinity" : "TextAffinity.downstream" ,'
+          ' "selectionIsDirectional": false,'
+          ' "composingBase": -1,'
+          ' "composingExtent": -1}';
+
+      final ByteData? messageBytes = const JSONMessageCodec().encodeMessage(<String, dynamic>{
+        'method': 'TextInputClient.updateEditingStateWithDeltas',
+        'args': <dynamic>[-1, jsonDecode('{"deltas": [$jsonDelta]}')],
+      });
+
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+        'flutter/textinput',
+        messageBytes,
+        (ByteData? _) {},
+      );
+      expect(record.length, 1);
+      // Verify the error message in parts because Web formats the message
+      // differently from others.
+      expect(record[0].exception.toString(), matches(RegExp(r'\bThe selection range: TextSelection.collapsed\(offset: 6, affinity: TextAffinity.downstream, isDirectional: false\)(?!\w)')));
+      expect(record[0].exception.toString(), matches(RegExp(r'\bis not within the bounds of text: hello of length: 5\b')));
+    });
+
+    test('Invalid TextRange fails loudly when being converted to JSON - Faulty Composing Region', () async {
+      final List<FlutterErrorDetails> record = <FlutterErrorDetails>[];
+      FlutterError.onError = (FlutterErrorDetails details) {
+        record.add(details);
+      };
+
+      final FakeDeltaTextInputClient client = FakeDeltaTextInputClient(const TextEditingValue(text: 'worl'));
+      const TextInputConfiguration configuration = TextInputConfiguration(enableDeltaModel: true);
+      TextInput.attach(client, configuration);
+
+      const String jsonDelta = '{'
+          '"oldText": "worl",'
+          ' "deltaText": "world",'
+          ' "deltaStart": 0,'
+          ' "deltaEnd": 4,'
+          ' "selectionBase": 5,'
+          ' "selectionExtent": 5,'
+          ' "selectionAffinity" : "TextAffinity.downstream" ,'
+          ' "selectionIsDirectional": false,'
+          ' "composingBase": 0,'
+          ' "composingExtent": 6}';
+
+      final ByteData? messageBytes = const JSONMessageCodec().encodeMessage(<String, dynamic>{
+        'method': 'TextInputClient.updateEditingStateWithDeltas',
+        'args': <dynamic>[-1, jsonDecode('{"deltas": [$jsonDelta]}')],
+      });
+
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+        'flutter/textinput',
+        messageBytes,
+        (ByteData? _) {},
+      );
+      expect(record.length, 1);
+      // Verify the error message in parts because Web formats the message
+      // differently from others.
+      expect(record[0].exception.toString(), matches(RegExp(r'\bThe composing range: TextRange\(start: 0, end: 6\)(?!\w)')));
+      expect(record[0].exception.toString(), matches(RegExp(r'\bis not within the bounds of text: world of length: 5\b')));
+    });
   });
 }
 

packages/flutter/test/services/text_editing_delta_test.dart

@@ -57,6 +57,19 @@ void main() {
       expect(delta.selection, expectedSelection);
       expect(delta.composing, expectedComposing);
     });
+
+    test('Verify invalid TextEditingDeltaInsertion fails to apply', () {
+      const TextEditingDeltaInsertion delta =
+              TextEditingDeltaInsertion(
+                oldText: 'hello worl',
+                textInserted: 'd',
+                insertionOffset: 11,
+                selection: TextSelection.collapsed(offset: 11),
+                composing: TextRange.empty,
+              );
+
+      expect(() { delta.apply(TextEditingValue.empty); }, throwsAssertionError);
+    });
   });
 
   group('TextEditingDeltaDeletion', () {
@@ -109,6 +122,18 @@ void main() {
       expect(delta.selection, expectedSelection);
       expect(delta.composing, expectedComposing);
     });
+
+    test('Verify invalid TextEditingDeltaDeletion fails to apply', () {
+      const TextEditingDeltaDeletion delta =
+              TextEditingDeltaDeletion(
+                oldText: 'hello world',
+                deletedRange: TextRange(start: 5, end: 12),
+                selection: TextSelection.collapsed(offset: 5),
+                composing: TextRange.empty,
+              );
+
+      expect(() { delta.apply(TextEditingValue.empty); }, throwsAssertionError);
+    });
   });
 
   group('TextEditingDeltaReplacement', () {
@@ -189,6 +214,19 @@ void main() {
       expect(delta.selection, expectedSelection);
       expect(delta.composing, expectedComposing);
     });
+
+    test('Verify invalid TextEditingDeltaReplacement fails to apply', () {
+      const TextEditingDeltaReplacement delta =
+              TextEditingDeltaReplacement(
+                oldText: 'hello worl',
+                replacementText: 'world',
+                replacedRange: TextRange(start: 5, end: 11),
+                selection: TextSelection.collapsed(offset: 11),
+                composing: TextRange.empty,
+              );
+
+      expect(() { delta.apply(TextEditingValue.empty); }, throwsAssertionError);
+    });
   });
 
   group('TextEditingDeltaNonTextUpdate', () {
@@ -213,5 +251,16 @@ void main() {
       expect(delta.selection, expectedSelection);
       expect(delta.composing, expectedComposing);
     });
+
+    test('Verify invalid TextEditingDeltaNonTextUpdate fails to apply', () {
+      const TextEditingDeltaNonTextUpdate delta =
+              TextEditingDeltaNonTextUpdate(
+                oldText: 'hello world',
+                selection: TextSelection.collapsed(offset: 12),
+                composing: TextRange.empty,
+              );
+
+      expect(() { delta.apply(TextEditingValue.empty); }, throwsAssertionError);
+    });
   });
 }