Merge pull request #591 from angularsen/fix-parsing-ambiguous-lowercase-units

Fix parsing ambiguous abbreviations when lowercase

Author: angularsen

UnitsNet.Tests/UnitParserTests.cs

@@ -65,6 +65,13 @@ public void Parse_AbbreviationCaseInsensitive_Uppercase_Years()
             Assert.Equal(expected, actual);
         }
 
+        [Fact]
+        public void Parse_GivenAbbreviationsThatAreAmbiguousWhenLowerCase_ReturnsCorrectUnit()
+        {
+            Assert.Equal(PressureUnit.Megabar, Pressure.ParseUnit("Mbar"));
+            Assert.Equal(PressureUnit.Millibar, Pressure.ParseUnit("mbar"));
+        }
+
         [Fact]
         public void Parse_UnknownAbbreviationThrowsUnitNotFoundException()
         {

UnitsNet/CustomCode/UnitParser.cs

@@ -90,7 +90,11 @@ object Parse([NotNull] string unitAbbreviation, Type unitType, [CanBeNull] IForm
             if(!_unitAbbreviationsCache.TryGetUnitValueAbbreviationLookup(unitType, formatProvider, out var abbreviations))
                 throw new UnitNotFoundException($"No abbreviations defined for unit type [{unitType}] for culture [{formatProvider}].");
 
-            var unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation);
+            var unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: true);
+
+            // Narrow the search if too many hits, for example Megabar "Mbar" and Millibar "mbar" need to be distinguished
+            if (unitIntValues.Count > 1)
+                unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: false);
 
             switch (unitIntValues.Count)
             {
@@ -191,7 +195,12 @@ bool TryParse(string unitAbbreviation, Type unitType, [CanBeNull] IFormatProvide
             if(!_unitAbbreviationsCache.TryGetUnitValueAbbreviationLookup(unitType, formatProvider, out var abbreviations))
                 return false;
 
-            var unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation);
+            var unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: true);
+
+            // Narrow the search if too many hits, for example Megabar "Mbar" and Millibar "mbar" need to be distinguished
+            if (unitIntValues.Count > 1)
+                unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: false);
+
             if(unitIntValues.Count != 1)
                 return false;
 

UnitsNet/CustomCode/UnitValueAbbreviationLookup.cs

@@ -31,14 +31,9 @@ namespace UnitsNet
 {
     internal class UnitValueAbbreviationLookup
     {
-        private UnitToAbbreviationMap unitToAbbreviationMap = new UnitToAbbreviationMap();
-        private AbbreviationToUnitMap abbreviationToUnitMap = new AbbreviationToUnitMap();
-
-        internal UnitValueAbbreviationLookup()
-        {
-            unitToAbbreviationMap = new UnitToAbbreviationMap();
-            abbreviationToUnitMap = new AbbreviationToUnitMap();
-        }
+        private readonly UnitToAbbreviationMap unitToAbbreviationMap = new UnitToAbbreviationMap();
+        private readonly AbbreviationToUnitMap abbreviationToUnitMap = new AbbreviationToUnitMap();
+        private readonly AbbreviationToUnitMap lowerCaseAbbreviationToUnitMap = new AbbreviationToUnitMap();
 
         internal string[] GetAllUnitAbbreviationsForQuantity()
         {
@@ -61,32 +56,43 @@ internal List<string> GetAbbreviationsForUnit(int unit)
             return abbreviations.Distinct().ToList();
         }
 
-        internal List<int> GetUnitsForAbbreviation(string abbreviation)
+        internal List<int> GetUnitsForAbbreviation(string abbreviation, bool ignoreCase)
         {
             var lowerCaseAbbreviation = abbreviation.ToLower();
-            if(!abbreviationToUnitMap.TryGetValue(lowerCaseAbbreviation, out var units))
-                abbreviationToUnitMap[lowerCaseAbbreviation] = units = new List<int>();
+            var key = ignoreCase ? lowerCaseAbbreviation : abbreviation;
+            var map = ignoreCase ? lowerCaseAbbreviationToUnitMap : abbreviationToUnitMap;
+
+            if(!map.TryGetValue(key, out List<int> units))
+                map[key] = units = new List<int>();
 
             return units.Distinct().ToList();
         }
 
         internal void Add(int unit, string abbreviation, bool setAsDefault = false)
         {
             var lowerCaseAbbreviation = abbreviation.ToLower();
+
             if(!unitToAbbreviationMap.TryGetValue(unit, out var abbreviationsForUnit))
                 abbreviationsForUnit = unitToAbbreviationMap[unit] = new List<string>();
 
-            if(!abbreviationToUnitMap.TryGetValue(lowerCaseAbbreviation, out var unitsForAbbreviation))
-                abbreviationToUnitMap[lowerCaseAbbreviation] = unitsForAbbreviation = new List<int>();
+            if(!abbreviationToUnitMap.TryGetValue(abbreviation, out var unitsForAbbreviation))
+                abbreviationToUnitMap[abbreviation] = unitsForAbbreviation = new List<int>();
+
+            if(!lowerCaseAbbreviationToUnitMap.TryGetValue(lowerCaseAbbreviation, out var unitsForLowerCaseAbbreviation))
+                lowerCaseAbbreviationToUnitMap[lowerCaseAbbreviation] = unitsForLowerCaseAbbreviation = new List<int>();
+
+            unitsForLowerCaseAbbreviation.Remove(unit);
+            unitsForLowerCaseAbbreviation.Add(unit);
 
-            abbreviationsForUnit.Remove(abbreviation);
             unitsForAbbreviation.Remove(unit);
+            unitsForAbbreviation.Add(unit);
 
+            abbreviationsForUnit.Remove(abbreviation);
             if (setAsDefault)
                 abbreviationsForUnit.Insert(0, abbreviation);
             else
                 abbreviationsForUnit.Add(abbreviation);
-            unitsForAbbreviation.Add(unit);
+
         }
     }
 }