Open Radar

 
Area:
UIKit

Summary:
A UILabel with text only consisting of line breaks is taller than text containing line breaks and other characters.

Steps to Reproduce:
1. Download the sample project.
2. Build and run on any iOS simulator
3. Notice the assertion fails because of different sizes.

The code is actually really simple to reproduce:

    let label1 = UILabel(frame: .zero)
    label1.text = "\n"
    let label1Size = label1.systemLayoutSizeFitting(UILayoutFittingCompressedSize)

    let label2 = UILabel(frame: .zero)
    label2.text = "a\n"
    let label2Size = label2.systemLayoutSizeFitting(UILayoutFittingCompressedSize)

    assert(label1Size == label2Size) // fails

Expected Results:
A UILabel with the text "\n" should have the same height as a UILabel with the text "a\n". 

Actual Results:
A UILabel with the text "\n" has double the height as a UILabel with the text "a\n". The issue is still reproduced even if the label's numberOfLines property is set to 1.

Version/Build:
Xcode Version 9.2 (9C40b)
iOS 11.1 Simulator (Any device type)