done (#82286)

packages/flutter/lib/src/rendering/editable.dart

@@ -3194,7 +3194,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   @override
   double computeMaxIntrinsicWidth(double height) {
     _layoutText(maxWidth: double.infinity);
-    return _textPainter.maxIntrinsicWidth + cursorWidth;
+    return _textPainter.maxIntrinsicWidth + _caretMargin;
   }
 
   /// An estimate of the height of a line in the text. See [TextPainter.preferredLineHeight].

packages/flutter/test/material/text_field_test.dart

@@ -6611,6 +6611,7 @@ void main() {
     // the cursor regardless of alignment.
     stepWidth = null;
     const double WIDTH_OF_CHAR = 16.0;
+    const double CARET_GAP = 1.0;
     await tester.pumpWidget(buildFrame(
       stepWidth: stepWidth,
       cursorWidth: 18.0,
@@ -6618,7 +6619,7 @@ void main() {
     ));
     await tester.enterText(find.byType(TextField), text);
     await tester.pumpAndSettle();
-    expect(tester.getSize(find.byType(TextField)).width, WIDTH_OF_CHAR * text.length + 18.0);
+    expect(tester.getSize(find.byType(TextField)).width, WIDTH_OF_CHAR * text.length + 18.0 + CARET_GAP);
     await tester.pumpWidget(buildFrame(
       stepWidth: stepWidth,
       cursorWidth: 18.0,
@@ -6626,7 +6627,7 @@ void main() {
     ));
     await tester.enterText(find.byType(TextField), text);
     await tester.pumpAndSettle();
-    expect(tester.getSize(find.byType(TextField)).width, WIDTH_OF_CHAR * text.length + 18.0);
+    expect(tester.getSize(find.byType(TextField)).width, WIDTH_OF_CHAR * text.length + 18.0 + CARET_GAP);
   });
 
   testWidgets('TextField style is merged with theme', (WidgetTester tester) async {

packages/flutter/test/rendering/editable_test.dart

@@ -85,7 +85,7 @@ void main() {
     );
     expect(editable.getMinIntrinsicWidth(double.infinity), 50.0);
     // The width includes the width of the cursor (1.0).
-    expect(editable.getMaxIntrinsicWidth(double.infinity), 51.0);
+    expect(editable.getMaxIntrinsicWidth(double.infinity), 52.0);
     expect(editable.getMinIntrinsicHeight(double.infinity), 10.0);
     expect(editable.getMaxIntrinsicHeight(double.infinity), 10.0);