Set [InputDecoration.floatingLabelBehavior] default to null (#70683)

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

@@ -2518,7 +2518,7 @@ class InputDecoration {
       'This feature was deprecated after v1.13.2.'
     )
     this.hasFloatingPlaceholder = true,
-    this.floatingLabelBehavior = FloatingLabelBehavior.auto,
+    this.floatingLabelBehavior,
     this.isCollapsed = false,
     this.isDense,
     this.contentPadding,
@@ -2564,7 +2564,7 @@ class InputDecoration {
       'This feature was deprecated after v1.13.2.'
     )
     this.hasFloatingPlaceholder = true,
-    this.floatingLabelBehavior = FloatingLabelBehavior.auto,
+    this.floatingLabelBehavior,
     this.hintStyle,
     this.filled = false,
     this.fillColor,
@@ -2752,9 +2752,9 @@ class InputDecoration {
   ///
   /// When [FloatingLabelBehavior.never] the label will always appear in an empty
   /// field in place of the content.
-  ///
-  /// Defaults to [FloatingLabelBehavior.auto].
   /// {@endtemplate}
+  ///
+  /// If null, [InputDecorationTheme.floatingLabelBehavior] will be used.
   final FloatingLabelBehavior? floatingLabelBehavior;
 
   /// Whether the [InputDecorator.child] is part of a dense form (i.e., uses less vertical
@@ -3700,6 +3700,8 @@ class InputDecorationTheme with Diagnosticable {
   final bool hasFloatingPlaceholder;
 
   /// {@macro flutter.material.inputDecoration.floatingLabelBehavior}
+  ///
+  /// Defaults to [FloatingLabelBehavior.auto].
   final FloatingLabelBehavior floatingLabelBehavior;
 
   /// Whether the input decorator's child is part of a dense form (i.e., uses

packages/flutter/test/material/input_decorator_test.dart

@@ -3052,7 +3052,7 @@ void main() {
     );
     expect(
       child.toString(),
-      "InputDecorator-[<'key'>](decoration: InputDecoration(floatingLabelBehavior: FloatingLabelBehavior.auto), baseStyle: TextStyle(<all styles inherited>), isFocused: false, isEmpty: false)",
+      "InputDecorator-[<'key'>](decoration: InputDecoration(), baseStyle: TextStyle(<all styles inherited>), isFocused: false, isEmpty: false)",
     );
   });
 

packages/flutter/test/material/text_field_test.dart

@@ -7524,7 +7524,7 @@ void main() {
 
     expect(description, <String>[
       'enabled: false',
-      'decoration: InputDecoration(labelText: "foo", floatingLabelBehavior: FloatingLabelBehavior.auto)',
+      'decoration: InputDecoration(labelText: "foo")',
       'style: TextStyle(inherit: true, color: Color(0xff00ff00))',
       'autofocus: true',
       'autocorrect: false',
@@ -8691,4 +8691,58 @@ void main() {
     expect(inputWidth, wideWidth);
     expect(cursorRight, inputWidth - kCaretGap);
   });
+
+  // Regressing test for https://github.com/flutter/flutter/issues/70625
+  testWidgets('TextFields can inherit [FloatingLabelBehaviour] from InputDecorationTheme.', (WidgetTester tester) async {
+    final FocusNode focusNode = FocusNode();
+    Widget textFieldBuilder({FloatingLabelBehavior behavior = FloatingLabelBehavior.auto, }) {
+      return MaterialApp(
+        theme: ThemeData(
+          inputDecorationTheme: InputDecorationTheme(
+            floatingLabelBehavior: behavior,
+          ),
+        ),
+        home: Scaffold(
+          body: TextField(
+            focusNode: focusNode,
+            decoration: const InputDecoration(
+              labelText: 'Label',
+            ),
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(textFieldBuilder(behavior: FloatingLabelBehavior.auto));
+    // The label will be positioned within the content when unfocused.
+    expect(tester.getTopLeft(find.text('Label')).dy, 20.0);
+
+    focusNode.requestFocus();
+    await tester.pumpAndSettle(); // label animation.
+    // The label will float above the content when focused.
+    expect(tester.getTopLeft(find.text('Label')).dy, 12.0);
+
+    focusNode.unfocus();
+    await tester.pumpAndSettle(); // label animation.
+
+    await tester.pumpWidget(textFieldBuilder(behavior: FloatingLabelBehavior.never));
+    await tester.pumpAndSettle(); // theme animation.
+    // The label will be positioned within the content.
+    expect(tester.getTopLeft(find.text('Label')).dy, 20.0);
+
+    focusNode.requestFocus();
+    await tester.pumpAndSettle(); // label animation.
+    // The label will always be positioned within the content.
+    expect(tester.getTopLeft(find.text('Label')).dy, 20.0);
+
+    await tester.pumpWidget(textFieldBuilder(behavior: FloatingLabelBehavior.always));
+    await tester.pumpAndSettle(); // theme animation.
+    // The label will always float above the content.
+    expect(tester.getTopLeft(find.text('Label')).dy, 12.0);
+
+    focusNode.unfocus();
+    await tester.pumpAndSettle(); // label animation.
+    // The label will always float above the content.
+    expect(tester.getTopLeft(find.text('Label')).dy, 12.0);
+  });
 }