Fix for negative zero with feet inches parsing. Added tests (#675)

Author: tmilnthorp

UnitsNet.Tests/CustomCode/LengthTests.FeetInches.cs

@@ -34,6 +34,10 @@ public void FeetInchesRoundTrip()
         [InlineData("1′", 1)] // Feet only
         [InlineData("1\"", 0.08333333)] // Inches only
         [InlineData("1″", 0.08333333)] // Inches only
+        [InlineData("0' 1\"", 0.08333333)] // Inches only
+        [InlineData("0' 1″", 0.08333333)] // Inches only
+        [InlineData("0′ 1\"", 0.08333333)] // Inches only
+        [InlineData("0′ 1″", 0.08333333)] // Inches only
         [InlineData("1' 1\"", 1.08333333)] // Normal form
         [InlineData("1′ 1″", 1.08333333)] // Normal form
         [InlineData(" 1′ 1″ ", 1.08333333)] // Normal form, requires trimming
@@ -45,6 +49,10 @@ public void FeetInchesRoundTrip()
         [InlineData("-1′", -1)] // Feet only
         [InlineData("-1\"", -0.08333333)] // Inches only
         [InlineData("-1″", -0.08333333)] // Inches only
+        [InlineData("-0' 1\"", -0.08333333)] // Inches only
+        [InlineData("-0' 1″", -0.08333333)] // Inches only
+        [InlineData("-0′ 1\"", -0.08333333)] // Inches only
+        [InlineData("-0′ 1″", -0.08333333)] // Inches only
         [InlineData("-1' 1\"", -1.08333333)] // Normal form
         [InlineData("-1′ 1″", -1.08333333)] // Normal form
         [InlineData(" -1′ 1″ ", -1.08333333)] // Normal form, requires trimming

UnitsNet/CustomCode/Quantities/Length.extra.cs

@@ -88,17 +88,24 @@ public static bool TryParseFeetInches([CanBeNull] string str, out Length result,
             string inchRegex = quantityParser.CreateRegexPatternForUnit(LengthUnit.Inch, formatProvider, matchEntireString: false);
 
             // Match entire string exactly
-            string pattern = $@"^(?<feet>{footRegex})\s?(?<inches>{inchRegex})$";
+            string pattern = $@"^(?<negativeSign>\-?)(?<feet>{footRegex})\s?(?<inches>{inchRegex})$";
 
             var match = new Regex(pattern, RegexOptions.Singleline).Match(str);
-            if (!match.Success) return false;
+            if (!match.Success)
+                return false;
 
+            var negativeSignGroup = match.Groups["negativeSign"];
             var feetGroup = match.Groups["feet"];
             var inchesGroup = match.Groups["inches"];
+
             if (TryParse(feetGroup.Value, formatProvider, out Length feet) &&
                 TryParse(inchesGroup.Value, formatProvider, out Length inches))
             {
-                result = feet.Value >= 0 ? feet + inches : feet - inches;
+                result = feet + inches;
+
+                if(negativeSignGroup.Length > 0)
+                    result = -result;
+
                 return true;
             }