Fix adjust-color handling of transparent values #319

* Consider the alpha channel if transparent is given as input (was previously ignored, and would return 'black')
* Return literal 'transparent' untouched if it was given as input, without parameters

Author: mkgl

src/main/java/com/vaadin/sass/internal/parser/function/AdjustColorFunctionGenerator.java

@@ -43,12 +43,17 @@ protected SassListItem computeForArgumentList(LexicalUnitImpl function,
         checkParams(function, actualArguments);
         LexicalUnitImpl color = getColor(function, actualArguments);
         float alpha = 1;
-        if (ColorUtil.isRgba(color) || ColorUtil.isHsla(color)) {
+        if (ColorUtil.isTransparent(color)) {
+            alpha = 0f;
+        } else if (ColorUtil.isRgba(color) || ColorUtil.isHsla(color)) {
             int lastIndex = color.getParameterList().size() - 1;
             alpha = color.getParameterList().get(lastIndex).getContainedValue()
                     .getFloatValue();
         }
         Float[] adjustBy = getAdjustments(function, actualArguments);
+        if (!anySet(adjustBy, 0, 7) && ColorUtil.isTransparent(color)) {
+            return LexicalUnitImpl.createIdent(ColorUtil.transparent);
+        }
         if (adjustBy[6] != null) {
             if ("adjust-color".equals(functionName)) {
                 alpha += adjustBy[6];

src/main/java/com/vaadin/sass/internal/util/ColorUtil.java

@@ -35,7 +35,7 @@ public class ColorUtil {
             .compile("#([0-9a-fA-F]{3}|[0-9a-fA-F]{6})");
     private static Map<String, String> colorNameToHex = new HashMap<String, String>();
     private static Map<String, String> hexToColorName = new HashMap<String, String>();
-    private static String transparent = "transparent";
+    public static String transparent = "transparent";
 
     static {
         colorNameToHex.put("aqua", "#00ffff");