Fix TextInput placeholder keeping a removed lineHeight on iOS

packages/react-native/Libraries/Text/TextInput/Singleline/RCTUITextField.mm

@@ -168,6 +168,15 @@ - (void)setDisableKeyboardShortcuts:(BOOL)disableKeyboardShortcuts
     [textAttributes removeObjectForKey:NSForegroundColorAttributeName];
   }
 
+  // UITextField's placeholder label keeps the paragraph style of the previous placeholder and applies it to a
+  // placeholder that has none, so a line height that was removed from the text attributes would still be used.
+  // A paragraph style matching the label's initial one avoids that.
+  if (textAttributes[NSParagraphStyleAttributeName] == nil) {
+    NSMutableParagraphStyle *paragraphStyle = [NSMutableParagraphStyle new];
+    paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
+    textAttributes[NSParagraphStyleAttributeName] = paragraphStyle;
+  }
+
   return textAttributes;
 }
 

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

@@ -0,0 +1,57 @@
+/*
+ * 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/RCTUITextField.h>
+#import <XCTest/XCTest.h>
+
+static NSParagraphStyle *RCTPlaceholderParagraphStyle(RCTUITextField *textField)
+{
+  return [textField.attributedPlaceholder attribute:NSParagraphStyleAttributeName atIndex:0 effectiveRange:NULL];
+}
+
+@interface RCTUITextFieldTests : XCTestCase
+@end
+
+@implementation RCTUITextFieldTests
+
+- (void)testPlaceholderDropsLineHeightRemovedFromTextAttributes
+{
+  NSMutableParagraphStyle *lineHeightParagraphStyle = [NSMutableParagraphStyle new];
+  lineHeightParagraphStyle.minimumLineHeight = 34;
+  lineHeightParagraphStyle.maximumLineHeight = 34;
+  RCTUITextField *textField = [RCTUITextField new];
+  textField.placeholder = @"Search";
+  textField.defaultTextAttributes = @{
+    NSFontAttributeName : [UIFont systemFontOfSize:17],
+    NSParagraphStyleAttributeName : lineHeightParagraphStyle,
+  };
+
+  textField.defaultTextAttributes = @{NSFontAttributeName : [UIFont systemFontOfSize:17]};
+
+  NSParagraphStyle *paragraphStyle = RCTPlaceholderParagraphStyle(textField);
+  XCTAssertNotNil(paragraphStyle);
+  XCTAssertEqual(paragraphStyle.minimumLineHeight, 0);
+  XCTAssertEqual(paragraphStyle.maximumLineHeight, 0);
+  XCTAssertEqual(paragraphStyle.lineBreakMode, NSLineBreakByTruncatingTail);
+}
+
+- (void)testPlaceholderKeepsParagraphStyleFromTextAttributes
+{
+  NSMutableParagraphStyle *paragraphStyle = [NSMutableParagraphStyle new];
+  paragraphStyle.alignment = NSTextAlignmentCenter;
+  RCTUITextField *textField = [RCTUITextField new];
+  textField.placeholder = @"Search";
+
+  textField.defaultTextAttributes = @{
+    NSFontAttributeName : [UIFont systemFontOfSize:17],
+    NSParagraphStyleAttributeName : paragraphStyle,
+  };
+
+  XCTAssertEqual(RCTPlaceholderParagraphStyle(textField).alignment, NSTextAlignmentCenter);
+}
+
+@end