fixes to 'effect' and 'trace'

src/main/java/carpet/script/CarpetExpression.java

@@ -2070,11 +2070,12 @@ public class CarpetExpression
      * <h3><code>query(e,'trace', reach?, options?...)</code></h3>
      * <p>Returns the result of ray tracing from entity perspective, indicating what it is looking at. Default reach is 4.5
      * blocks (5 for creative players), and by default it traces for blocks and entities, identical to player attack tracing action.
-     * This can be customized with <code>options</code>, use 'blocks' to trace for blocks only, 'liquids' to include liquid blocks
+     * This can be customized with <code>options</code>, use 'blocks' to trace for blocks, 'liquids' to include liquid blocks
-     * as possible results, and 'entities' to trace entities as well.</p>
+     * as possible results, and 'entities' to trace entities. Any combination of the above is possible. When tracing
+     * entities and blocks, blocks will take over the priority even if transparent or non-colliding (aka fighting chickens
+     * in tall grass).</p>
      * <p>Regardless of the options selected, the result could be <code>null</code> if nothing is in reach, entity, if look
-     * targets an antity, and block value if block is in reach. Tracing always hits blocks. Even if an entity tracing is requested
+     * targets an entity, and block value if block is in reach.</p>
-     * and there is a block in the way - the block will be returned.</p>
      * <h3><code>query(e,'nbt',path?)</code></h3>
      * <p>Returns full NBT of the entity. If path is specified, it fetches only that portion of the NBT,
      * that corresponds to the path. For specification of <code>path</code> attribute, consult
@@ -2131,9 +2132,9 @@ public class CarpetExpression
      * <h3><code>modify(e, 'no_clip', boolean)</code></h3>
      * <p>Sets if the entity obeys any collisions, including collisions with the terrain and basic physics.
      * Not affecting players, since they are controlled client side</p>
-     * <h3><code>modify(e, 'effect', name, duration, amplifier?, show_particles?, show_icon?)</code></h3>
+     * <h3><code>modify(e, 'effect', name, duration?, amplifier?, show_particles?, show_icon?)</code></h3>
      * <p>Applies status effect to the living entity. Takes several optional parameters, which default to <code>0</code>,
-     * <code>true</code> and <code>true</code>.</p>
+     * <code>true</code> and <code>true</code>. If no duration is specified, or it is null or 0, the effect is removed.</p>
      * <h3><code>modify(e, 'home', null), modify(e, 'home', block, distance?), modify(e, 'home', x, y, z, distance?)</code></h3>
      * <p>Sets AI to stay around the home position, within <code>distance</code> blocks from it. <code>distance</code>
      * defaults to 16 blocks. <code>null</code> removes it. <i>May</i> not work fully with mobs that have this AI built in, like

src/main/java/carpet/script/value/EntityValue.java

@@ -385,6 +385,7 @@ public class EntityValue extends Value
             float reach = 4.5f;
             boolean entities = true;
             boolean liquids = false;
+            boolean blocks = true;
 
             if (a!=null)
             {
@@ -401,12 +402,14 @@ public class EntityValue extends Value
                     if (args.size() > 1)
                     {
                         entities = false;
+                        blocks = false;
                         for (int i = 1; i < args.size(); i++)
                         {
                             String what = args.get(i).getString();
                             if (what.equalsIgnoreCase("entities"))
                                 entities = true;
-                            else if (what.equalsIgnoreCase("blocks")) {}
+                            else if (what.equalsIgnoreCase("blocks"))
+                                blocks = true;
                             else if (what.equalsIgnoreCase("liquids"))
                                 liquids = true;
                             else throw new InternalExpressionException("Incorrect tracing: "+what);
@@ -420,11 +423,14 @@ public class EntityValue extends Value
             }
 
             HitResult hitres;
-            if (entities)
+            if (entities && !blocks)
+                hitres = Tracer.rayTraceEntities(e, 1, reach, reach*reach);
+            else if (entities)
                 hitres = Tracer.rayTrace(e, 1, reach, liquids);
             else
                 hitres = Tracer.rayTraceBlocks(e, 1, reach, liquids);
 
+            if (hitres == null) return Value.NULL;
             switch (hitres.getType())
             {
                 case MISS: return Value.NULL;
@@ -796,13 +802,23 @@ public class EntityValue extends Value
             else if (v instanceof ListValue)
             {
                 List<Value> lv = ((ListValue) v).getItems();
-                if (lv.size() >= 2 && lv.size() <= 5)
+                if (lv.size() >= 1 && lv.size() <= 5)
                 {
                     String effectName = lv.get(0).getString();
                     StatusEffect effect = Registry.STATUS_EFFECT.get(new Identifier(effectName));
                     if (effect == null)
                         throw new InternalExpressionException("Wrong effect name: "+effectName);
+                    if (lv.size() == 1)
+                    {
+                        le.removeStatusEffect(effect);
+                        return;
+                    }
                     int duration = (int)NumericValue.asNumber(lv.get(1)).getLong();
+                    if (duration <= 0)
+                    {
+                        le.removeStatusEffect(effect);
+                        return;
+                    } 
                     int amplifier = 0;
                     if (lv.size() > 2)
                         amplifier = (int)NumericValue.asNumber(lv.get(2)).getLong();