Prevent registration of defaultLiterals and added more tests

src/main/java/com/mojang/brigadier/CommandDispatcher.java

@@ -93,6 +93,8 @@ public class CommandDispatcher<S> {
      * @return the node added to this tree
      */
     public LiteralCommandNode<S> register(final LiteralArgumentBuilder<S> command) {
+        if(command.isDefaultNode()) throw new IllegalArgumentException("Cannot add a default node to root");
+
         final LiteralCommandNode<S> build = command.build();
         root.addChild(build);
         return build;

src/main/java/com/mojang/brigadier/tree/LiteralCommandNode.java

@@ -22,7 +22,6 @@ import java.util.function.Predicate;
 public class LiteralCommandNode<S> extends CommandNode<S> {
     private final String literal;
 
-    
     public LiteralCommandNode(final String literal, final Command<S> command, final Predicate<S> requirement, final CommandNode<S> redirect, final RedirectModifier<S> modifier, final boolean forks) {
         this(literal, command, requirement, redirect, modifier, forks, null, false);
     }

src/test/java/com/mojang/brigadier/CommandDispatcherTest.java

@@ -53,6 +53,11 @@ public class CommandDispatcherTest {
         return result;
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void testRegisterDefaultNode() throws Exception {
+        subject.register(defaultLiteral("foo"));
+    }
+
     @SuppressWarnings("unchecked")
     @Test
     public void testCreateAndExecuteCommand() throws Exception {

src/test/java/com/mojang/brigadier/CommandDispatcherUsagesTest.java

@@ -13,7 +13,9 @@ import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 
 import java.util.Map;
+import java.util.stream.Collectors;
 
+import static com.mojang.brigadier.builder.LiteralArgumentBuilder.defaultLiteral;
 import static com.mojang.brigadier.builder.LiteralArgumentBuilder.literal;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.emptyArray;
@@ -97,14 +99,28 @@ public class CommandDispatcherUsagesTest {
             literal("k")
                 .redirect(get("h"))
         );
+        //default node tests
+        subject.register(
+            literal("l")
+                //basic
+                .then(defaultLiteral("1").executes(command))
+                //two choices
+                .then(literal("2")
+                    .then(defaultLiteral("i").executes(command))
+                    .then(literal("ii").executes(command)))
+                //chained
+                .then(literal("3").then(defaultLiteral("i").then(defaultLiteral("ii").executes(command))))
+                //unexecutable default node
+                .then(literal("4").then(defaultLiteral("i").then(literal("ii").executes(command))))
+        );
     }
 
     private CommandNode<Object> get(final String command) {
-        return Iterables.getLast(subject.parse(command, source).getContext().getNodes()).getNode();
+        return Iterables.getLast(subject.parse(command, source).getContext().getNodes().stream().filter(n -> !n.getRange().isEmpty()).collect(Collectors.toList())).getNode();
     }
 
     private CommandNode<Object> get(final StringReader command) {
-        return Iterables.getLast(subject.parse(command, source).getContext().getNodes()).getNode();
+        return Iterables.getLast(subject.parse(command, source).getContext().getNodes().stream().filter(n -> !n.getRange().isEmpty()).collect(Collectors.toList())).getNode();
     }
 
     @Test
@@ -148,6 +164,15 @@ public class CommandDispatcherUsagesTest {
             "i 2",
             "j ...",
             "k -> h",
+            "l",
+            "l 1",
+            "l 2",
+            "l 2 i",
+            "l 2 ii",
+            "l 3",
+            "l 3 i",
+            "l 3 i ii",
+            "l 4 i ii",
         }));
     }
 
@@ -165,6 +190,7 @@ public class CommandDispatcherUsagesTest {
             .put(get("i"), "i [1|2]")
             .put(get("j"), "j ...")
             .put(get("k"), "k -> h")
+            .put(get("l"), "l [1|2|3|4]")
             .build()
         ));
     }
@@ -193,4 +219,16 @@ public class CommandDispatcherUsagesTest {
             .build()
         ));
     }
+
+    @Test
+    public void testSmartUsage_l() throws Exception {
+        final Map<CommandNode<Object>, String> results = subject.getSmartUsage(get("l"), source);
+        assertThat(results, equalTo(ImmutableMap.builder()
+            .put(get("l 1"), "1")
+            .put(get("l 2"), "2 [i|ii]")
+            .put(get("l 3"), "3 [i]")
+            .put(get("l 4"), "4 i ii")
+            .build()
+        ));
+    }
 }

src/test/java/com/mojang/brigadier/builder/ArgumentBuilderTest.java

@@ -4,10 +4,12 @@
 package com.mojang.brigadier.builder;
 
 import com.mojang.brigadier.tree.CommandNode;
+import com.mojang.brigadier.tree.LiteralCommandNode;
 import org.junit.Before;
 import org.junit.Test;
 
 import static com.mojang.brigadier.arguments.IntegerArgumentType.integer;
+import static com.mojang.brigadier.builder.LiteralArgumentBuilder.defaultLiteral;
 import static com.mojang.brigadier.builder.LiteralArgumentBuilder.literal;
 import static com.mojang.brigadier.builder.RequiredArgumentBuilder.argument;
 import static org.hamcrest.Matchers.hasSize;
@@ -55,6 +57,20 @@ public class ArgumentBuilderTest {
         builder.then(literal("foo"));
     }
 
+    @Test
+    public void testThen_withDefaultNode() throws Exception {
+        final LiteralCommandNode<Object> child = defaultLiteral("foo").build();
+        builder.then(child);
+
+        assertThat(builder.getDefaultNode(), is(child));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testThen_withTwoDefaultNodes() throws Exception {
+        builder.then(defaultLiteral("foo"));
+        builder.then(defaultLiteral("bar"));
+    }
+
     private static class TestableArgumentBuilder<S> extends ArgumentBuilder<S, TestableArgumentBuilder<S>> {
         public TestableArgumentBuilder() {
             super(false);

src/test/java/com/mojang/brigadier/builder/RequiredArgumentBuilderTest.java

@@ -17,6 +17,7 @@ import static com.mojang.brigadier.builder.RequiredArgumentBuilder.argument;
 import static com.mojang.brigadier.builder.RequiredArgumentBuilder.defaultArgument;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.nullValue;
 import static org.junit.Assert.assertThat;
 
 @RunWith(MockitoJUnitRunner.class)
@@ -40,6 +41,7 @@ public class RequiredArgumentBuilderTest {
         assertThat(node.getName(), is("foo"));
         assertThat(node.getType(), is(type));
         assertThat(node.isDefaultNode(), is(false));
+        assertThat(node.getDefaultValue(), is(nullValue()));
     }
 
     @Test