Allow turning nodes back into builders without children

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

@@ -162,4 +162,8 @@ public class CommandDispatcher<S> {
 
         return nodes.toArray(new String[nodes.size()]);
     }
+
+    public RootCommandNode<S> getRoot() {
+        return root;
+    }
 }

src/main/java/com/mojang/brigadier/builder/ArgumentBuilder.java

@@ -28,7 +28,7 @@ public abstract class ArgumentBuilder<S, T extends ArgumentBuilder<S, T>> {
         return getThis();
     }
 
-    protected Command<S> getCommand() {
+    public Command<S> getCommand() {
         return command;
     }
 

src/main/java/com/mojang/brigadier/builder/LiteralArgumentBuilder.java

@@ -19,7 +19,7 @@ public class LiteralArgumentBuilder<S> extends ArgumentBuilder<S, LiteralArgumen
         return this;
     }
 
-    private String getLiteral() {
+    public String getLiteral() {
         return literal;
     }
 

src/main/java/com/mojang/brigadier/builder/RequiredArgumentBuilder.java

@@ -22,11 +22,11 @@ public class RequiredArgumentBuilder<S, T> extends ArgumentBuilder<S, RequiredAr
         return this;
     }
 
-    private CommandArgumentType<T> getType() {
+    public CommandArgumentType<T> getType() {
         return type;
     }
 
-    private String getName() {
+    public String getName() {
         return name;
     }
 

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

@@ -2,6 +2,8 @@ package com.mojang.brigadier.tree;
 
 import com.mojang.brigadier.Command;
 import com.mojang.brigadier.arguments.CommandArgumentType;
+import com.mojang.brigadier.builder.ArgumentBuilder;
+import com.mojang.brigadier.builder.RequiredArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.context.ParsedArgument;
 import com.mojang.brigadier.exceptions.CommandException;
@@ -60,6 +62,16 @@ public class ArgumentCommandNode<S, T> extends CommandNode<S> {
         type.listSuggestions(command, output);
     }
 
+    @Override
+    public RequiredArgumentBuilder<S, T> createBuilder() {
+        final RequiredArgumentBuilder<S, T> builder = RequiredArgumentBuilder.argument(name, type);
+        builder.requires(getRequirement());
+        if (getCommand() != null) {
+            builder.executes(getCommand());
+        }
+        return builder;
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;

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

@@ -2,6 +2,7 @@ package com.mojang.brigadier.tree;
 
 import com.google.common.collect.Maps;
 import com.mojang.brigadier.Command;
+import com.mojang.brigadier.builder.ArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandException;
 
@@ -65,6 +66,10 @@ public abstract class CommandNode<S> {
         return 31 * children.hashCode() + (command != null ? command.hashCode() : 0);
     }
 
+    public Predicate<S> getRequirement() {
+        return requirement;
+    }
+
     protected abstract Object getMergeKey();
 
     public abstract String getUsageText();
@@ -72,4 +77,6 @@ public abstract class CommandNode<S> {
     public abstract String parse(String command, CommandContextBuilder<S> contextBuilder) throws CommandException;
 
     public abstract void listSuggestions(String command, Set<String> output);
+
+    public abstract ArgumentBuilder<S, ?> createBuilder();
 }

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

@@ -2,6 +2,8 @@ package com.mojang.brigadier.tree;
 
 import com.mojang.brigadier.Command;
 import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.builder.ArgumentBuilder;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandException;
 import com.mojang.brigadier.exceptions.ParameterizedCommandExceptionType;
@@ -70,4 +72,14 @@ public class LiteralCommandNode<S> extends CommandNode<S> {
         result = 31 * result + super.hashCode();
         return result;
     }
+
+    @Override
+    public LiteralArgumentBuilder<S> createBuilder() {
+        final LiteralArgumentBuilder<S> builder = LiteralArgumentBuilder.literal(this.literal);
+        builder.requires(getRequirement());
+        if (getCommand() != null) {
+            builder.executes(getCommand());
+        }
+        return builder;
+    }
 }

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

@@ -1,5 +1,6 @@
 package com.mojang.brigadier.tree;
 
+import com.mojang.brigadier.builder.ArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandException;
 
@@ -35,4 +36,9 @@ public class RootCommandNode<S> extends CommandNode<S> {
         if (!(o instanceof RootCommandNode)) return false;
         return super.equals(o);
     }
+
+    @Override
+    public ArgumentBuilder<S, ?> createBuilder() {
+        throw new IllegalStateException("Cannot convert root into a builder");
+    }
 }

src/test/java/com/mojang/brigadier/tree/ArgumentCommandNodeTest.java

@@ -5,6 +5,7 @@ import com.google.common.collect.Sets;
 import com.google.common.testing.EqualsTester;
 import com.mojang.brigadier.Command;
 import com.mojang.brigadier.arguments.IntegerArgumentType;
+import com.mojang.brigadier.builder.RequiredArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandException;
 import org.junit.Before;
@@ -105,4 +106,13 @@ public class ArgumentCommandNodeTest extends AbstractCommandNodeTest {
             )
             .testEquals();
     }
+
+    @Test
+    public void testCreateBuilder() throws Exception {
+        final RequiredArgumentBuilder<Object, Integer> builder = node.createBuilder();
+        assertThat(builder.getName(), is(node.getName()));
+        assertThat(builder.getType(), is(node.getType()));
+        assertThat(builder.getRequirement(), is(node.getRequirement()));
+        assertThat(builder.getCommand(), is(node.getCommand()));
+    }
 }

src/test/java/com/mojang/brigadier/tree/LiteralCommandNodeTest.java

@@ -4,6 +4,8 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Sets;
 import com.google.common.testing.EqualsTester;
 import com.mojang.brigadier.Command;
+import com.mojang.brigadier.builder.ArgumentBuilder;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandException;
 import org.junit.Before;
@@ -117,4 +119,12 @@ public class LiteralCommandNodeTest extends AbstractCommandNodeTest {
             )
             .testEquals();
     }
+
+    @Test
+    public void testCreateBuilder() throws Exception {
+        final LiteralArgumentBuilder<Object> builder = node.createBuilder();
+        assertThat(builder.getLiteral(), is(node.getLiteral()));
+        assertThat(builder.getRequirement(), is(node.getRequirement()));
+        assertThat(builder.getCommand(), is(node.getCommand()));
+    }
 }

src/test/java/com/mojang/brigadier/tree/RootCommandNodeTest.java

@@ -48,6 +48,11 @@ public class RootCommandNodeTest extends AbstractCommandNodeTest {
         assertThat(set, is(empty()));
     }
 
+    @Test(expected = IllegalStateException.class)
+    public void testCreateBuilder() throws Exception {
+        node.createBuilder();
+    }
+
     @Test
     public void testEquals() throws Exception {
         new EqualsTester()