Fix wrong redirect behavior (MC-256419) (#124)

* Fix wrong redirect behavior

* Set foundCommand to `true` if redirect modifier returns no result.

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

@@ -231,7 +231,6 @@ public class CommandDispatcher<S> {
                 if (child != null) {
                     forked |= context.isForked();
                     if (child.hasNodes()) {
-                        foundCommand = true;
                         final RedirectModifier<S> modifier = context.getRedirectModifier();
                         if (modifier == null) {
                             if (next == null) {
@@ -248,6 +247,8 @@ public class CommandDispatcher<S> {
                                     for (final S source : results) {
                                         next.add(child.copyFor(source));
                                     }
+                                } else {
+                                    foundCommand = true;
                                 }
                             } catch (final CommandSyntaxException ex) {
                                 consumer.onCommandComplete(context, false, 0);

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

@@ -4,6 +4,7 @@
 package com.mojang.brigadier;
 
 import com.google.common.collect.Lists;
+import com.mojang.brigadier.arguments.IntegerArgumentType;
 import com.mojang.brigadier.context.CommandContext;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
@@ -14,6 +15,9 @@ import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 
+import java.util.Collections;
+import java.util.concurrent.atomic.AtomicBoolean;
+
 import static com.mojang.brigadier.arguments.IntegerArgumentType.integer;
 import static com.mojang.brigadier.builder.LiteralArgumentBuilder.literal;
 import static com.mojang.brigadier.builder.RequiredArgumentBuilder.argument;
@@ -326,6 +330,37 @@ public class CommandDispatcherTest {
         verify(command).run(argThat(hasProperty("source", is(source2))));
     }
 
+    @Test
+    public void testIncompleteRedirectShouldThrow() {
+        final LiteralCommandNode<Object> foo = subject.register(literal("foo")
+            .then(literal("bar")
+                .then(argument("value", integer()).executes(context -> IntegerArgumentType.getInteger(context, "value"))))
+            .then(literal("awa").executes(context -> 2)));
+        final LiteralCommandNode<Object> baz = subject.register(literal("baz").redirect(foo));
+        try {
+            int result = subject.execute("baz bar", source);
+            fail("Should have thrown an exception");
+        } catch (CommandSyntaxException e) {
+            assertThat(e.getType(), is(CommandSyntaxException.BUILT_IN_EXCEPTIONS.dispatcherUnknownCommand()));
+        }
+    }
+
+    @Test
+    public void testRedirectModifierEmptyResult() {
+        final LiteralCommandNode<Object> foo = subject.register(literal("foo")
+            .then(literal("bar")
+                .then(argument("value", integer()).executes(context -> IntegerArgumentType.getInteger(context, "value"))))
+            .then(literal("awa").executes(context -> 2)));
+        final RedirectModifier<Object> emptyModifier = context -> Collections.emptyList();
+        final LiteralCommandNode<Object> baz = subject.register(literal("baz").fork(foo, emptyModifier));
+        try {
+            int result = subject.execute("baz bar 100", source);
+            assertThat(result, is(0)); // No commands executed, so result is 0
+        } catch (CommandSyntaxException e) {
+            fail("Should not throw an exception");
+        }
+    }
+
     @Test
     public void testExecuteOrphanedSubcommand() throws Exception {
         subject.register(literal("foo").then(