Move default unit converter registration to quantity types (#1018)

Ref #1016 

Instead of a huge single method in UnitConverter, it is split up into a static method per quanitity type.

Author: tmilnthorp

CodeGen/Generators/UnitsNetGen/QuantityGenerator.cs

@@ -344,6 +344,42 @@ private void GenerateStaticMethods()
 
         #region Static Methods
 
+        /// <summary>
+        /// Registers the default conversion functions in the given <see cref=""UnitConverter""/> instance.
+        /// </summary>
+        /// <param name=""unitConverter"">The <see cref=""UnitConverter""/> to register the default conversion functions in.</param>
+        internal static void RegisterDefaultConversions(UnitConverter unitConverter)
+        {{
+            // Register in unit converter: BaseUnit -> {_quantity.Name}Unit");
+
+        foreach(var unit in _quantity.Units)
+        {
+            if(unit.SingularName == _quantity.BaseUnit)
+                continue;
+
+            Writer.WL( $@"
+            unitConverter.SetConversionFunction<{_quantity.Name}>({_unitEnumName}.{_quantity.BaseUnit}, {_quantity.Name}Unit.{unit.SingularName}, quantity => quantity.ToUnit({_quantity.Name}Unit.{unit.SingularName}));");
+        }
+
+        Writer.WL( $@"
+            
+            // Register in unit converter: BaseUnit <-> BaseUnit
+            unitConverter.SetConversionFunction<{_quantity.Name}>({_unitEnumName}.{_quantity.BaseUnit}, {_unitEnumName}.{_quantity.BaseUnit}, quantity => quantity);
+
+            // Register in unit converter: {_quantity.Name}Unit -> BaseUnit" );
+
+        foreach(var unit in _quantity.Units)
+        {
+            if(unit.SingularName == _quantity.BaseUnit)
+                continue;
+
+            Writer.WL($@"
+            unitConverter.SetConversionFunction<{_quantity.Name}>({_quantity.Name}Unit.{unit.SingularName}, {_unitEnumName}.{_quantity.BaseUnit}, quantity => quantity.ToBaseUnit());" );
+        }
+
+        Writer.WL( $@"
+        }}
+
         /// <summary>
         ///     Get unit abbreviation string.
         /// </summary>

CodeGen/Generators/UnitsNetGen/UnitConverterGenerator.cs

@@ -69,7 +69,6 @@ public static void Generate(string rootDir, Quantity[] quantities)
             GenerateUnitAbbreviationsCache(quantities, $"{outputDir}/UnitAbbreviationsCache.g.cs");
             GenerateQuantityType(quantities, $"{outputDir}/QuantityType.g.cs");
             GenerateStaticQuantity(quantities, $"{outputDir}/Quantity.g.cs");
-            GenerateUnitConverter(quantities, $"{outputDir}/UnitConverter.g.cs");
 
             var unitCount = quantities.SelectMany(q => q.Units).Count();
             Log.Information("");
@@ -143,12 +142,5 @@ private static void GenerateStaticQuantity(Quantity[] quantities, string filePat
             File.WriteAllText(filePath, content);
             Log.Information("✅ Quantity.g.cs");
         }
-
-        private static void GenerateUnitConverter(Quantity[] quantities, string filePath)
-        {
-            var content = new UnitConverterGenerator(quantities).Generate();
-            File.WriteAllText(filePath, content);
-            Log.Information("✅ UnitConverter.g.cs");
-        }
     }
 }