LengthFormatter: rounding error

Number:rdar://FB8208224 Date Originated:07/28/2020
Status:Open Resolved:
Product: Product Version:
Classification: Reproducible:
LengthFormatter.string(fromMeters:) contains a bug when rounding values that are <0.5 short of an even foot.


let formatter = LengthFormatter()
formatter.numberFormatter.maximumFractionDigits = 0
formatter.locale = Locale(identifier: "en_US")
let meters = 1.82
let formattedString = formatter.string(from: meters)

// formattedString is "5 ft 12 in"
// Expected value should be "6 ft 0in"

This is because the value of `1.82 meters` converts to ~71.65 inches. 

However, the calculations "feet = floor(value / 12)" and "inches = value % 12" occur _before_ LengthFormatter.numberFormatter performs its rounding operations, and there is no second check on the rounded inch value to see if feet/inches need to be recalculated afterward


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