Fixed variable remove counter costs to work also correctly if X=0 (e.g. Retribution of the Ancients and Willbreaker).

Mage.Tests/src/test/java/org/mage/test/cards/control/ItThatBetraysTest.java

@@ -27,7 +27,6 @@
  */
 package org.mage.test.cards.control;
 
-import mage.abilities.keyword.HasteAbility;
 import mage.constants.PhaseStep;
 import mage.constants.Zone;
 import org.junit.Test;
@@ -37,15 +36,15 @@ import org.mage.test.serverside.base.CardTestPlayerBase;
  *
  * @author LevelX2
  */
-
 public class ItThatBetraysTest extends CardTestPlayerBase {
 
     /**
      * https://github.com/magefree/mage/issues/796
      *
-     * When an opponent sacrifices a fetchland and you have an It That Betrays in play,
-     * sacrificing the fetchland that comes under your control from its ability returns
-     * it to play under your control, allowing you to fetch infinite lands.
+     * When an opponent sacrifices a fetchland and you have an It That Betrays
+     * in play, sacrificing the fetchland that comes under your control from its
+     * ability returns it to play under your control, allowing you to fetch
+     * infinite lands.
      *
      */
     @Test
@@ -62,7 +61,7 @@ public class ItThatBetraysTest extends CardTestPlayerBase {
 
         assertLife(playerA, 19);
         assertLife(playerB, 19);
-        
+
         // Going to graveyard if player B sacrifices it
         assertGraveyardCount(playerA, "Flooded Strand", 1);
     }
@@ -71,7 +70,7 @@ public class ItThatBetraysTest extends CardTestPlayerBase {
     @Test
     public void testExileItThatBetraysEffect() {
         addCard(Zone.BATTLEFIELD, playerA, "Flooded Strand", 1);
-        
+
         addCard(Zone.BATTLEFIELD, playerA, "Rest in Peace", 1);
 
         addCard(Zone.BATTLEFIELD, playerB, "It That Betrays");
@@ -83,7 +82,7 @@ public class ItThatBetraysTest extends CardTestPlayerBase {
 
         assertLife(playerA, 19);
         assertLife(playerB, 20);
-        
+
         // Player B now controls a Flooded Strand, even though it went to exile
         assertPermanentCount(playerB, "Flooded Strand", 1);
     }

Mage.Tests/src/test/java/org/mage/test/cards/control/WillbreakerTest.java

@@ -0,0 +1,73 @@
+/*
+ *  Copyright 2010 BetaSteward_at_googlemail.com. All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without modification, are
+ *  permitted provided that the following conditions are met:
+ *
+ *     1. Redistributions of source code must retain the above copyright notice, this list of
+ *        conditions and the following disclaimer.
+ *
+ *     2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *        of conditions and the following disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY BetaSteward_at_googlemail.com ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ *  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BetaSteward_at_googlemail.com OR
+ *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ *  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ *  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ *  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *  The views and conclusions contained in the software and documentation are those of the
+ *  authors and should not be interpreted as representing official policies, either expressed
+ *  or implied, of BetaSteward_at_googlemail.com.
+ */
+package org.mage.test.cards.control;
+
+import mage.constants.PhaseStep;
+import mage.constants.Zone;
+import org.junit.Test;
+import org.mage.test.serverside.base.CardTestPlayerBase;
+
+/**
+ *
+ * @author LevelX2
+ */
+public class WillbreakerTest extends CardTestPlayerBase {
+
+    /**
+     * http://www.slightlymagic.net/forum/viewtopic.php?f=70&t=17664&start=120#p186736
+     *
+     * I tried to activate Retribution of the Ancients while I only controlled
+     * Nantuko Husk and Willbreaker without +1/+1 counters on them. The program
+     * didn't let me activate the RotA, even though the creature you choose
+     * doesn't need to have any counters on it (X can be 0, doesn't say
+     * otherwise on the card and it isn't a target requirement). It asked me to
+     * pay B, then choose a creature I controlled, which I did... and then
+     * nothing happened.
+     *
+     */
+    @Test
+    public void testRetributionOfTheAncientsZeroCounter() {
+        addCard(Zone.BATTLEFIELD, playerA, "Swamp", 1);
+        // {B}, Remove X +1/+1 counters from among creatures you control: Target creature gets -X/-X until end of turn.
+        addCard(Zone.BATTLEFIELD, playerA, "Retribution of the Ancients", 1); // Enchantment {B}
+        // Whenever a creature an opponent controls becomes the target of a spell or ability you control, gain control of that creature for as long as you control Willbreaker.
+        addCard(Zone.BATTLEFIELD, playerA, "Willbreaker", 1);
+
+        addCard(Zone.BATTLEFIELD, playerB, "Silvercoat Lion");
+
+        activateAbility(1, PhaseStep.PRECOMBAT_MAIN, playerA, "{B},Remove", "Silvercoat Lion");
+        setChoice(playerA, "X=0");
+
+        setStopAt(1, PhaseStep.BEGIN_COMBAT);
+        execute();
+
+        assertPermanentCount(playerA, "Willbreaker", 1);
+        assertPermanentCount(playerA, "Silvercoat Lion", 1);
+    }
+
+}

Mage/src/mage/abilities/costs/VariableCostImpl.java

@@ -157,8 +157,7 @@ public abstract class VariableCostImpl implements Cost, VariableCost {
         Player controller = game.getPlayer(source.getControllerId());
         if (controller != null) {
             xValue = controller.announceXCost(getMinValue(source, game), getMaxValue(source, game),
-                    new StringBuilder("Announce the number of ").append(actionText).toString(),
-                    game, source, this);
+                    "Announce the number of " + actionText, game, source, this);
         }
         return xValue;
     }

Mage/src/mage/abilities/costs/common/RemoveCounterCost.java

@@ -84,6 +84,9 @@ public class RemoveCounterCost extends CostImpl {
         int countersRemoved = 0;
         Player controller = game.getPlayer(controllerId);
         if (controller != null) {
+            if (countersToRemove == 0) { // Can happen when used for X costs where X = 0;
+                return paid = true;
+            }
             target.clearChosen();
             if (target.choose(Outcome.UnboostCreature, controllerId, sourceId, game)) {
                 for (UUID targetId : target.getTargets()) {