Label unnecessarily ellided (#59807)

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

@@ -986,9 +986,15 @@ class _RenderDecoration extends RenderBox {
       + contentPadding.right));
     // Increase the available width for the label when it is scaled down.
     final double invertedLabelScale = lerpDouble(1.00, 1 / _kFinalLabelScale, decoration.floatingLabelProgress);
+    final double labelWidth = math.max(0.0, constraints.maxWidth - (
+      _boxSize(icon).width
+      + contentPadding.left
+      + _boxSize(prefixIcon).width
+      + _boxSize(suffixIcon).width
+      + contentPadding.right));
     boxToBaseline[label] = _layoutLineBox(
       label,
-      boxConstraints.copyWith(maxWidth: inputWidth * invertedLabelScale),
+      boxConstraints.copyWith(maxWidth: labelWidth * invertedLabelScale),
     );
     boxToBaseline[hint] = _layoutLineBox(
       hint,

packages/flutter/test/material/input_decorator_test.dart

@@ -4158,4 +4158,64 @@ void main() {
 
     expect(tester.getTopLeft(find.text(hintText)).dy, topPosition);
   });
+
+  testWidgets("InputDecorator label width isn't affected by prefix or suffix", (WidgetTester tester) async {
+    const String labelText = 'My Label';
+    const String prefixText = 'The five boxing wizards jump quickly.';
+    const String suffixText = 'Suffix';
+
+    Widget getLabeledInputDecorator(bool showFix) {
+      return MaterialApp(
+        home: Material(
+          child: Builder(
+            builder: (BuildContext context) {
+              return Theme(
+                data: Theme.of(context),
+                child: Align(
+                  alignment: Alignment.topLeft,
+                  child: TextField(
+                    decoration: InputDecoration(
+                      icon: const Icon(Icons.assistant),
+                      prefixText: showFix ? prefixText : null,
+                      suffixText: showFix ? suffixText : null,
+                      suffixIcon: const Icon(Icons.threesixty),
+                      labelText: labelText,
+                    ),
+                  ),
+                ),
+              );
+            },
+          ),
+        ),
+      );
+    }
+
+    // Build with no prefix or suffix.
+    await tester.pumpWidget(getLabeledInputDecorator(false));
+
+    // Get the width of the label when there is no prefix/suffix.
+    expect(find.text(prefixText), findsNothing);
+    expect(find.text(suffixText), findsNothing);
+    final double labelWidth = tester.getSize(find.text(labelText)).width;
+
+    // Build with a prefix and suffix.
+    await tester.pumpWidget(getLabeledInputDecorator(true));
+
+    // The prefix and suffix exist but aren't visible. They have not affected
+    // the width of the label.
+    expect(find.text(prefixText), findsOneWidget);
+    expect(getOpacity(tester, prefixText), 0.0);
+    expect(find.text(suffixText), findsOneWidget);
+    expect(getOpacity(tester, suffixText), 0.0);
+    expect(tester.getSize(find.text(labelText)).width, labelWidth);
+
+    // Tap to focus.
+    await tester.tap(find.byType(TextField));
+    await tester.pumpAndSettle();
+
+    // The prefix and suffix are visible, and the label is floating and still
+    // hasn't had its width affected.
+    expect(tester.getSize(find.text(labelText)).width, labelWidth);
+    expect(getOpacity(tester, prefixText), 1.0);
+  });
 }