Deprecate maxLengthEnforced for text fields (#72043)

packages/flutter/lib/src/cupertino/text_field.dart

@@ -262,6 +262,11 @@ class CupertinoTextField extends StatefulWidget {
     this.minLines,
     this.expands = false,
     this.maxLength,
+    @Deprecated(
+      'Use maxLengthEnforcement parameter which provides more specific '
+      'behavior related to the maxLength limit. '
+      'This feature was deprecated after v1.25.0-5.0.pre.'
+    )
     this.maxLengthEnforced = true,
     this.maxLengthEnforcement,
     this.onChanged,
@@ -409,6 +414,11 @@ class CupertinoTextField extends StatefulWidget {
     this.minLines,
     this.expands = false,
     this.maxLength,
+    @Deprecated(
+      'Use maxLengthEnforcement parameter which provides more specific '
+      'behavior related to the maxLength limit. '
+      'This feature was deprecated after v1.25.0-5.0.pre.'
+    )
     this.maxLengthEnforced = true,
     this.maxLengthEnforcement,
     this.onChanged,
@@ -654,6 +664,11 @@ class CupertinoTextField extends StatefulWidget {
   ///
   /// If true, prevents the field from allowing more than [maxLength]
   /// characters.
+  @Deprecated(
+    'Use maxLengthEnforcement parameter which provides more specific '
+    'behavior related to the maxLength limit. '
+    'This feature was deprecated after v1.25.0-5.0.pre.'
+  )
   final bool maxLengthEnforced;
 
   /// Determines how the [maxLength] limit should be enforced.
@@ -808,7 +823,7 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with Restoratio
   FocusNode get _effectiveFocusNode => widget.focusNode ?? (_focusNode ??= FocusNode());
 
   MaxLengthEnforcement get _effectiveMaxLengthEnforcement => widget.maxLengthEnforcement
-    ?? LengthLimitingTextInputFormatter.inferredDefaultMaxLengthEnforcement;
+    ?? LengthLimitingTextInputFormatter.getDefaultMaxLengthEnforcement();
 
   bool _showSelectionHandles = false;
 

packages/flutter/lib/src/material/text_field.dart

@@ -359,6 +359,11 @@ class TextField extends StatefulWidget {
     this.minLines,
     this.expands = false,
     this.maxLength,
+    @Deprecated(
+      'Use maxLengthEnforcement parameter which provides more specific '
+      'behavior related to the maxLength limit. '
+      'This feature was deprecated after v1.25.0-5.0.pre.'
+    )
     this.maxLengthEnforced = true,
     this.maxLengthEnforcement,
     this.onChanged,
@@ -606,6 +611,11 @@ class TextField extends StatefulWidget {
   ///
   /// If true, prevents the field from allowing more than [maxLength]
   /// characters.
+  @Deprecated(
+    'Use maxLengthEnforcement parameter which provides more specific '
+    'behavior related to the maxLength limit. '
+    'This feature was deprecated after v1.25.0-5.0.pre.'
+  )
   final bool maxLengthEnforced;
 
   /// Determines how the [maxLength] limit should be enforced.
@@ -856,7 +866,7 @@ class _TextFieldState extends State<TextField> with RestorationMixin implements
   FocusNode get _effectiveFocusNode => widget.focusNode ?? (_focusNode ??= FocusNode());
 
   MaxLengthEnforcement get _effectiveMaxLengthEnforcement => widget.maxLengthEnforcement
-    ?? LengthLimitingTextInputFormatter.inferredDefaultMaxLengthEnforcement;
+    ?? LengthLimitingTextInputFormatter.getDefaultMaxLengthEnforcement(Theme.of(context).platform);
 
   bool _isHovering = false;
 

packages/flutter/lib/src/material/text_form_field.dart

@@ -165,6 +165,11 @@ class TextFormField extends FormField<String> {
       'This feature was deprecated after v1.19.0.'
     )
     bool autovalidate = false,
+    @Deprecated(
+      'Use maxLengthEnforcement parameter which provides more specific '
+      'behavior related to the maxLength limit. '
+      'This feature was deprecated after v1.25.0-5.0.pre.'
+    )
     bool maxLengthEnforced = true,
     MaxLengthEnforcement? maxLengthEnforcement,
     int? maxLines = 1,

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

@@ -415,7 +415,8 @@ class LengthLimitingTextInputFormatter extends TextInputFormatter {
   /// {@macro flutter.services.textFormatter.maxLengthEnforcement}
   final MaxLengthEnforcement? maxLengthEnforcement;
 
-  /// Return an effective [MaxLengthEnforcement] according the target platform.
+  /// Returns a [MaxLengthEnforcement] that follows the specified [platform]'s
+  /// convention.
   ///
   /// {@template flutter.services.textFormatter.effectiveMaxLengthEnforcement}
   /// ### Platform specific behaviors
@@ -432,11 +433,13 @@ class LengthLimitingTextInputFormatter extends TextInputFormatter {
   ///    [MaxLengthEnforcement.truncateAfterCompositionEnds]. These platforms
   ///    allow the composition to exceed by default.
   /// {@endtemplate}
-  static MaxLengthEnforcement get inferredDefaultMaxLengthEnforcement {
+  static MaxLengthEnforcement getDefaultMaxLengthEnforcement([
+    TargetPlatform? platform,
+  ]) {
     if (kIsWeb) {
       return MaxLengthEnforcement.truncateAfterCompositionEnds;
     } else {
-      switch (defaultTargetPlatform) {
+      switch (platform ?? defaultTargetPlatform) {
         case TargetPlatform.android:
         case TargetPlatform.windows:
           return MaxLengthEnforcement.enforced;
@@ -493,7 +496,7 @@ class LengthLimitingTextInputFormatter extends TextInputFormatter {
 
     assert(maxLength > 0);
 
-    switch (maxLengthEnforcement ?? inferredDefaultMaxLengthEnforcement) {
+    switch (maxLengthEnforcement ?? getDefaultMaxLengthEnforcement()) {
       case MaxLengthEnforcement.none:
         return newValue;
       case MaxLengthEnforcement.enforced:

packages/flutter/test/services/text_formatter_test.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -460,6 +461,28 @@ void main() {
         expect(formatted.text, 'bbbbbbbbbb');
       });
     });
+
+    group('get enforcement from target platform', () {
+      // The enforcement on Web will be always `MaxLengthEnforcement.truncateAfterCompositionEnds`
+
+      test('with TargetPlatform.windows', () async {
+        final MaxLengthEnforcement enforcement = LengthLimitingTextInputFormatter.getDefaultMaxLengthEnforcement(
+          TargetPlatform.windows,
+        );
+        if (kIsWeb) {
+          expect(enforcement, MaxLengthEnforcement.truncateAfterCompositionEnds);
+        } else {
+          expect(enforcement, MaxLengthEnforcement.enforced);
+        }
+      });
+
+      test('with TargetPlatform.macOS', () async {
+        final MaxLengthEnforcement enforcement = LengthLimitingTextInputFormatter.getDefaultMaxLengthEnforcement(
+          TargetPlatform.macOS,
+        );
+        expect(enforcement, MaxLengthEnforcement.truncateAfterCompositionEnds);
+      });
+    });
   });
 
   test('FilteringTextInputFormatter should return the old value if new value contains non-white-listed character', () {