Fix multiline TextInput placeholder missing or clipped on iOS when it changes without a resize

packages/react-native/Libraries/Text/TextInput/Multiline/RCTUITextView.mm

@@ -396,6 +396,9 @@ - (void)_updatePlaceholder
   _placeholderView.attributedText = [[NSAttributedString alloc] initWithString:_placeholder ?: @""
                                                                     attributes:[self _placeholderTextAttributes]];
   [self _invalidatePlaceholderVisibility];
+  // `layoutSubviews` sizes the placeholder label to fit its text, and the new text may need a different size. Nothing
+  // else lays the label out again when this view keeps its size (also after it is recycled).
+  [self setNeedsLayout];
 }
 
 - (NSDictionary<NSAttributedStringKey, id> *)_placeholderTextAttributes

packages/react-native/React/Tests/Text/RCTUITextViewTests.mm

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <React/RCTUITextView.h>
+#import <XCTest/XCTest.h>
+
+static UILabel *RCTPlaceholderLabel(RCTUITextView *textView)
+{
+  for (UIView *subview in textView.subviews) {
+    if ([subview isKindOfClass:[UILabel class]]) {
+      return (UILabel *)subview;
+    }
+  }
+  return nil;
+}
+
+@interface RCTUITextViewTests : XCTestCase
+@end
+
+@implementation RCTUITextViewTests
+
+- (void)testPlaceholderIsLaidOutWhenSetOnALaidOutView
+{
+  RCTUITextView *textView = [[RCTUITextView alloc] initWithFrame:CGRectMake(0, 0, 340, 122)];
+  [textView layoutIfNeeded];
+
+  textView.placeholder = @"Type 5 characters to show length helper";
+  [textView layoutIfNeeded];
+
+  XCTAssertNotNil(RCTPlaceholderLabel(textView));
+  XCTAssertGreaterThan(CGRectGetHeight(RCTPlaceholderLabel(textView).frame), 0);
+}
+
+- (void)testPlaceholderIsLaidOutWhenItGetsLongerOnALaidOutView
+{
+  RCTUITextView *textView = [[RCTUITextView alloc] initWithFrame:CGRectMake(0, 0, 340, 122)];
+  textView.placeholder = @"Short placeholder";
+  [textView layoutIfNeeded];
+  CGFloat oneLineHeight = CGRectGetHeight(RCTPlaceholderLabel(textView).frame);
+
+  textView.placeholder = @"Tell us why you're interested in this position and what you would bring to the team";
+  [textView layoutIfNeeded];
+
+  XCTAssertGreaterThan(CGRectGetHeight(RCTPlaceholderLabel(textView).frame), oneLineHeight);
+}
+
+@end