Merge pull request #2 from desmondinho/feat/merge-nullable

feat: improve nullability support

src/TwMerge.cs

@@ -31,10 +31,15 @@ public TwMerge()
     /// </summary>
     /// <param name="classNames">The collection of CSS classes to be merged.</param>
     /// <returns>A <see langword="string"/> of merged CSS classes.</returns>
-    public string Merge( params string[] classNames )
+    public string? Merge( params string?[] classNames )
     {
         var joinedClassNames = string.Join( ' ', classNames );
 
+        if( string.IsNullOrEmpty( joinedClassNames ) )
+        {
+            return null;
+        }
+
         if( _cache.TryGetValue( joinedClassNames, out var cachedResult ) )
         {
             return cachedResult;
@@ -54,7 +59,7 @@ private string Merge( string classList )
 
         var filteredClassNames = FilterConflictingClasses( classes );
 
-        return string.Join( " ", filteredClassNames );
+        return string.Join( ' ', filteredClassNames );
     }
 
     private ClassInfo GetClassInfo( string className )

src/TwMergeConfig.cs

@@ -1131,7 +1131,7 @@ private static readonly (string[] Items, Func<string, bool>[] Validators) _blur
          * Grayscale
          * See https://tailwindcss.com/docs/grayscale
          */
-        new ClassGroup( "grayscale", "grayscale", _zeroAndEmpty ),
+        new ClassGroup( "grayscale", "grayscale", _zeroAndEmpty, _arbitraryValue ),
         /*
          * Hue Rotate
          * See https://tailwindcss.com/docs/hue-rotate

tests/TwMergeTests.cs

@@ -0,0 +1,42 @@
+namespace TailwindMerge.Tests;
+
+public class TwMergeTests
+{
+    [Theory]
+    [InlineData( "mix-blend-normal mix-blend-multiply", "mix-blend-multiply" )]
+    [InlineData( "h-10 h-min", "h-min" )]
+    [InlineData( "stroke-black stroke-1", "stroke-black stroke-1" )]
+    [InlineData( "stroke-2 stroke-[3]", "stroke-[3]" )]
+    [InlineData( "outline-black outline-1", "outline-black outline-1" )]
+    [InlineData( "grayscale-0 grayscale-[50%]", "grayscale-[50%]" )]
+    [InlineData( "grow grow-[2]", "grow-[2]" )]
+    [InlineData( "", null )]
+    [InlineData( null, null )]
+    public void Merge_MergesCorrectly( string classList, string expected )
+    {
+        // Act
+        var actual = new TwMerge().Merge( classList );
+
+        // Assert
+        Assert.Equal( expected, actual );
+    }
+
+    [Fact]
+    public void Merge_SameValues_ReturnsCachedResult()
+    {
+        // Arrange
+        var twMerge = new TwMerge();
+
+        // Act
+        var actual = twMerge.Merge( "h-10 h-min" );
+
+        // Assert
+        Assert.Equal( "h-min", actual );
+
+        // Act
+        actual = twMerge.Merge( "h-10 h-min" );
+
+        // Assert
+        Assert.Equal( "h-min", actual );
+    }
+}