support nil in syntax

Author: riktenx

src/main/java/com/lootfilters/lang/Lexer.java

@@ -23,6 +23,7 @@ public class Lexer {
         put("true", Token.Type.TRUE);
         put("meta", Token.Type.META);
         put("rule", Token.Type.RULE);
+        put("nil", Token.Type.NIL);
         put("if", Token.Type.IF);
         put("&&", Token.Type.OP_AND);
         put("||", Token.Type.OP_OR);

src/main/java/com/lootfilters/lang/Parser.java

@@ -48,6 +48,7 @@
 import static com.lootfilters.lang.Token.Type.LITERAL_INT;
 import static com.lootfilters.lang.Token.Type.LITERAL_STRING;
 import static com.lootfilters.lang.Token.Type.META;
+import static com.lootfilters.lang.Token.Type.NIL;
 import static com.lootfilters.lang.Token.Type.OP_AND;
 import static com.lootfilters.lang.Token.Type.OP_NOT;
 import static com.lootfilters.lang.Token.Type.OP_OR;
@@ -179,9 +180,9 @@ private void parseRule(boolean isTerminal, int sourceLine) {
                 case "color":
                     builder.textColor(assign[1].expectColor()); break;
                 case "backgroundColor":
-                    builder.backgroundColor(assign[1].expectColor()); break;
+                    builder.backgroundColor(assign[1].expectColor(true)); break;
                 case "borderColor":
-                    builder.borderColor(assign[1].expectColor()); break;
+                    builder.borderColor(assign[1].expectColor(true)); break;
                 case "hidden":
                     builder.hidden(assign[1].expectBoolean()); break;
                 case "showLootbeam":
@@ -363,6 +364,13 @@ private Token[] parseAssignment() { // assignments do not support nested express
     private void parseIcon(DisplayConfig.Builder builder) {
         tokens.takeExpect(IDENTIFIER);
         tokens.takeExpect(ASSIGN);
+        if (tokens.peek().is(NIL)) {
+            tokens.takeExpect(NIL);
+            tokens.takeExpect(STMT_END);
+            builder.icon(null);
+            return;
+        }
+
         var type = tokens.takeExpect(IDENTIFIER);
         var args = tokens.takeArgList();
         if (type.getValue().equals("Sprite")) {

src/main/java/com/lootfilters/lang/Token.java

@@ -14,7 +14,7 @@ public enum Type {
         IF, APPLY, RULE,
         META,
         COLON, COMMA,
-        TRUE, FALSE,
+        TRUE, FALSE, NIL,
         IDENTIFIER,
         LITERAL_INT, LITERAL_STRING,
         ASSIGN,
@@ -53,7 +53,11 @@ public String expectString() {
         return value;
     }
 
-    public Color expectColor() {
+    public Color expectColor(boolean allowNil) {
+        if (allowNil && type == Type.NIL) {
+            return null;
+        }
+
         if (type != Type.LITERAL_STRING) {
             throw new ParseException("unexpected non-string token", this);
         }
@@ -65,6 +69,10 @@ public Color expectColor() {
         return color;
     }
 
+    public Color expectColor() {
+        return expectColor(false);
+    }
+
     public boolean expectBoolean() {
         switch (type) {
             case TRUE: return true;

src/main/java/com/lootfilters/lang/TokenStream.java

@@ -83,6 +83,7 @@ public Token takeExpectLiteral() {
         var first = take();
         if (!first.is(Token.Type.LITERAL_INT)
                 && !first.is(Token.Type.LITERAL_STRING)
+                && !first.is(Token.Type.NIL)
                 && !first.is(Token.Type.TRUE)
                 && !first.is(Token.Type.FALSE)) {
             throw new ParseException("unexpected non-literal token", first);

src/main/java/com/lootfilters/model/SoundProvider.java

@@ -17,6 +17,8 @@ public static SoundProvider fromExpr(Token token) throws ParseException {
                 return new SoundEffect(token.expectInt());
             case LITERAL_STRING:
                 return new File(token.expectString());
+            case NIL:
+                return null;
             default:
                 throw new ParseException("sound: unexpected token", token);
         }