hollow-cube/command-parser-fixes (#54)

* Rewrite CommandParserImpl recursively (fix #1327)

* Fix for tests: CommandManagerTest, CommandParseTest

* Make attributes final inside Chain

* fix #1295 with argument type priority

* Don't include command name in list of arguments

* Add test for #1327

* Add test for #1295

* Fix suggestions with bad syntax

* Fix #1916

* Add test for #1916

* add failing test

* mess with arg order

* Fix `GraphImpl` causing syntax order issues

---------

Co-authored-by: Spanner <spanner77@protonmail.com>

demo/src/main/java/net/minestom/demo/Main.java

@@ -58,6 +58,7 @@ public class Main {
         commandManager.register(new RedirectTestCommand());
         commandManager.register(new DisplayCommand());
         commandManager.register(new NotificationCommand());
+        commandManager.register(new TestCommand2());
 
         commandManager.setUnknownCommandCallback((sender, command) -> sender.sendMessage(Component.text("Unknown command", NamedTextColor.RED)));
 

demo/src/main/java/net/minestom/demo/PlayerInit.java

@@ -136,6 +136,14 @@ public class PlayerInit {
             })
             .addListener(PlayerBlockPlaceEvent.class, event -> {
 //                event.setDoBlockUpdates(false);
+            })
+            .addListener(PlayerBlockInteractEvent.class, event -> {
+                var block = event.getBlock();
+                var rawOpenProp = block.getProperty("open");
+                if (rawOpenProp == null) return;
+
+                block = block.withProperty("open", String.valueOf(!Boolean.parseBoolean(rawOpenProp)));
+                event.getInstance().setBlock(event.getBlockPosition(), block);
             });
 
     static {

demo/src/main/java/net/minestom/demo/commands/TestCommand2.java

@@ -0,0 +1,20 @@
+package net.minestom.demo.commands;
+
+import net.minestom.server.command.builder.Command;
+import net.minestom.server.command.builder.arguments.ArgumentType;
+
+public class TestCommand2 extends Command {
+    public TestCommand2() {
+        super("test2");
+
+        var argA = ArgumentType.String("a");
+        var argB = ArgumentType.String("b");
+
+        addSyntax((sender, context) -> {
+            sender.sendMessage("a only");
+        }, argA);
+        addSyntax((sender, context) -> {
+            sender.sendMessage("a and b");
+        }, argB, argA);
+    }
+}

src/main/java/net/minestom/server/command/CommandParserImpl.java

@@ -18,7 +18,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
-import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 final class CommandParserImpl implements CommandParser {
@@ -27,6 +26,7 @@ final class CommandParserImpl implements CommandParser {
 
     static final class Chain {
         CommandExecutor defaultExecutor = null;
+        SuggestionCallback suggestionCallback = null;
         final ArrayDeque<NodeResult> nodeResults = new ArrayDeque<>();
         final List<CommandCondition> conditions = new ArrayList<>();
         final List<CommandExecutor> globalListeners = new ArrayList<>();
@@ -60,81 +60,60 @@ final class CommandParserImpl implements CommandParser {
             return (sender, context) -> globalListeners.forEach(x -> x.apply(sender, context));
         }
 
-        SuggestionCallback extractSuggestionCallback() {
-            return nodeResults.peekLast().callback;
-        }
-
         Map<String, ArgumentResult<Object>> collectArguments() {
             return nodeResults.stream()
-                    .skip(1) // skip root
+                    .skip(2) // skip root node and command
                     .collect(Collectors.toUnmodifiableMap(NodeResult::name, NodeResult::argumentResult));
         }
 
         List<Argument<?>> getArgs() {
             return nodeResults.stream().map(x -> x.node.argument()).collect(Collectors.toList());
         }
+
+        Chain() {}
+
+        Chain(CommandExecutor defaultExecutor,
+              SuggestionCallback suggestionCallback,
+              ArrayDeque<NodeResult> nodeResults,
+              List<CommandCondition> conditions,
+              List<CommandExecutor> globalListeners) {
+            this.defaultExecutor = defaultExecutor;
+            this.suggestionCallback = suggestionCallback;
+            this.nodeResults.addAll(nodeResults);
+            this.conditions.addAll(conditions);
+            this.globalListeners.addAll(globalListeners);
+        }
+
+        Chain fork() {
+            return new Chain(defaultExecutor, suggestionCallback, nodeResults, conditions, globalListeners);
+        }
     }
 
     @Override
     public @NotNull CommandParser.Result parse(@NotNull CommandSender sender, @NotNull Graph graph, @NotNull String input) {
         final CommandStringReader reader = new CommandStringReader(input);
-        final Chain chain = new Chain();
+        Chain chain = new Chain();
-        // Read from input
-        NodeResult result;
         Node parent = graph.root();
-        while ((result = parseChild(sender, parent, reader)) != null) {
+
-            chain.append(result);
+        NodeResult result = parseNode(sender, parent, chain, reader);
-            if (result.argumentResult instanceof ArgumentResult.SyntaxError<?> e) {
+        chain = result.chain;
-                // Syntax error stop at this arg
+        if (result.argumentResult instanceof ArgumentResult.Success<?>) {
-                final ArgumentCallback argumentCallback = parent.argument().getCallback();
+            NodeResult lastNodeResult = chain.nodeResults.peekLast();
-                if (argumentCallback == null && chain.defaultExecutor != null) {
+            Node lastNode = lastNodeResult.node;
-                    return ValidCommand.defaultExecutor(input, chain);
+
-                } else {
+            CommandExecutor executor = nullSafeGetter(lastNode.execution(), Graph.Execution::executor);
-                    return new InvalidCommand(input, chain.mergedConditions(),
+            if (executor != null) return ValidCommand.executor(input, chain, executor);
-                            argumentCallback, e, chain.collectArguments(), chain.mergedGlobalExecutors(),
-                            chain.extractSuggestionCallback(), chain.getArgs());
-                }
-            }
-            parent = result.node;
         }
-        // Check children for arguments with default values
+        // If here, then the command failed or didn't have an executor
-        do {
+
-            Node tmp = parent;
+        // Look for a default executor, or give up if we got nowhere
-            parent = null;
+        NodeResult lastNode = chain.nodeResults.peekLast();
-            for (Node child : tmp.next()) {
+        if (lastNode.node.equals(parent)) return UnknownCommandResult.INSTANCE;
-                final Argument<?> argument = child.argument();
+        if (chain.defaultExecutor != null) {
-                final Function<CommandSender, ?> defaultSupplier = argument.getDefaultValue();
+            return ValidCommand.defaultExecutor(input, chain);
-                if (defaultSupplier != null) {
-                    final Object value = defaultSupplier.apply(sender);
-                    final ArgumentResult<Object> argumentResult = new ArgumentResult.Success<>(value, "");
-                    chain.append(new NodeResult(child, argumentResult, argument.getSuggestionCallback()));
-                    parent = child;
-                    break;
-                }
-            }
-        } while (parent != null);
-        // Check if any syntax has been found
-        final NodeResult lastNode = chain.nodeResults.peekLast();
-        if (lastNode == null) return UnknownCommandResult.INSTANCE;
-        // Verify syntax(s)
-        final CommandExecutor executor = nullSafeGetter(lastNode.node().execution(), Graph.Execution::executor);
-        if (executor == null) {
-            // Syntax error
-            if (chain.defaultExecutor != null) {
-                return ValidCommand.defaultExecutor(input, chain);
-            } else {
-                return InvalidCommand.invalid(input, chain);
-            }
         }
-        if (reader.hasRemaining()) {
+
-            // Command had trailing data
+        return InvalidCommand.invalid(input, chain);
-            if (chain.defaultExecutor != null) {
-                return ValidCommand.defaultExecutor(input, chain);
-            } else {
-                return InvalidCommand.invalid(input, chain);
-            }
-        }
-        return ValidCommand.executor(input, chain, executor);
     }
 
     @Contract("null, _ -> null; !null, null -> fail; !null, !null -> _")
@@ -142,32 +121,90 @@ final class CommandParserImpl implements CommandParser {
         return obj == null ? null : getter.apply(obj);
     }
 
-    private static NodeResult parseChild(@NotNull CommandSender sender, Node parent, CommandStringReader reader) {
+    private static NodeResult parseNode(@NotNull CommandSender sender, Node node, Chain chain, CommandStringReader reader) {
-        if (!reader.hasRemaining()) return null;
+        chain = chain.fork();
-        for (Node child : parent.next()) {
+        Argument<?> argument = node.argument();
-            final Argument<?> argument = child.argument();
+        int start = reader.cursor();
-            final int start = reader.cursor();
+
-            final ArgumentResult<?> parse = parse(sender, argument, reader);
+        if (reader.hasRemaining()) {
-            if (parse instanceof ArgumentResult.Success<?> success) {
+            ArgumentResult<?> result = parseArgument(sender, argument, reader);
-                return new NodeResult(child, (ArgumentResult<Object>) success,
+            SuggestionCallback suggestionCallback = argument.getSuggestionCallback();
-                        argument.getSuggestionCallback());
+            NodeResult nodeResult = new NodeResult(node, chain, (ArgumentResult<Object>) result, suggestionCallback);
-            } else if (parse instanceof ArgumentResult.SyntaxError<?> syntaxError) {
+            chain.append(nodeResult);
-                return new NodeResult(child, (ArgumentResult<Object>) syntaxError,
+            if (suggestionCallback != null) chain.suggestionCallback = suggestionCallback;
-                        argument.getSuggestionCallback());
+            if (chain.nodeResults.size() == 1) { // If this is the root node (usually "Literal<>")
+                reader.cursor(start);
             } else {
-                // Reset cursor & try next
+                if (!(result instanceof ArgumentResult.Success<?>)) {
+                    reader.cursor(start);
+                    return nodeResult;
+                }
+            }
+        } else {
+            // Nothing left, yet we're still being asked to parse? There must be defaults then
+            Function<CommandSender, ?> defaultSupplier = node.argument().getDefaultValue();
+            if (defaultSupplier != null) {
+                Object value = defaultSupplier.apply(sender);
+                ArgumentResult<Object> argumentResult = new ArgumentResult.Success<>(value, "");
+                chain.append(new NodeResult(node, chain, argumentResult, argument.getSuggestionCallback()));
+                // Add the default to the chain, and then carry on dealing with this node
+            } else {
+                // Still being asked to parse yet there's nothing left, syntax error.
+                return new NodeResult(
+                        node,
+                        chain,
+                        new ArgumentResult.SyntaxError<>("Not enough arguments","",-1),
+                        argument.getSuggestionCallback()
+                );
+            }
+        }
+        // Successfully matched this node's argument
+        start = reader.cursor();
+        if (!reader.hasRemaining()) start--; // This is needed otherwise the reader throws an AssertionError
+
+        NodeResult error = null;
+        for (Node child : node.next()) {
+            NodeResult childResult = parseNode(sender, child, chain, reader);
+            if (childResult.argumentResult instanceof ArgumentResult.Success<Object>) {
+                // Assume that there is only one successful node for a given chain of arguments
+                return childResult;
+            } else {
+                if (error == null) {
+                    // If this is the base argument (e.g. "teleport" in /teleport) then
+                    // do not report an argument to be incompatible, since the more
+                    // correct thing would be to say that the command is unknown.
+                    if (!(childResult.chain.nodeResults.size() == 2 && childResult.argumentResult instanceof ArgumentResult.IncompatibleType<?>)) {
+                        error = childResult;
+                    }
+                }
                 reader.cursor(start);
             }
         }
-        for (Node node : parent.next()) {
+        // None were successful. Either incompatible types, or syntax error. It doesn't matter to us, though
-            final SuggestionCallback suggestionCallback = node.argument().getSuggestionCallback();
+
-            if (suggestionCallback != null) {
+        // Try to execute this node
-                return new NodeResult(parent,
+        CommandExecutor executor = nullSafeGetter(node.execution(), Graph.Execution::executor);
-                        new ArgumentResult.SyntaxError<>("None of the arguments were compatible, but a suggestion callback was found.", "", -1),
+        if (executor == null) {
-                        suggestionCallback);
+            // Stuck here with no executor
+            if (error != null) {
+                return error;
+            } else {
+                return chain.nodeResults.peekLast();
             }
         }
-        return null;
+
+        if (reader.hasRemaining()) {
+            // Trailing data is a syntax error
+            return new NodeResult(
+                    node,
+                    chain,
+                    new ArgumentResult.SyntaxError<>("Command has trailing data", "", -1),
+                    argument.getSuggestionCallback()
+            );
+        }
+
+        // Command was successful!
+        return chain.nodeResults.peekLast();
     }
 
     record UnknownCommandResult() implements Result.UnknownCommand {
@@ -222,7 +259,7 @@ final class CommandParserImpl implements CommandParser {
             return new InvalidCommand(input, chain.mergedConditions(),
                     null/*todo command syntax callback*/,
                     new ArgumentResult.SyntaxError<>("Command has trailing data.", null, -1),
-                    chain.collectArguments(), chain.mergedGlobalExecutors(), chain.extractSuggestionCallback(), chain.getArgs());
+                    chain.collectArguments(), chain.mergedGlobalExecutors(), chain.suggestionCallback, chain.getArgs());
         }
 
         @Override
@@ -238,12 +275,12 @@ final class CommandParserImpl implements CommandParser {
 
         static ValidCommand defaultExecutor(String input, Chain chain) {
             return new ValidCommand(input, chain.mergedConditions(), chain.defaultExecutor, chain.collectArguments(),
-                    chain.mergedGlobalExecutors(), chain.extractSuggestionCallback(), chain.getArgs());
+                    chain.mergedGlobalExecutors(), chain.suggestionCallback, chain.getArgs());
         }
 
         static ValidCommand executor(String input, Chain chain, CommandExecutor executor) {
             return new ValidCommand(input, chain.mergedConditions(), executor, chain.collectArguments(), chain.mergedGlobalExecutors(),
-                    chain.extractSuggestionCallback(), chain.getArgs());
+                    chain.suggestionCallback, chain.getArgs());
         }
 
         @Override
@@ -321,7 +358,7 @@ final class CommandParserImpl implements CommandParser {
         static final ExecutableCommand.Result INVALID_SYNTAX = new ExecutionResultImpl(Type.INVALID_SYNTAX, null);
     }
 
-    private record NodeResult(Node node, ArgumentResult<Object> argumentResult, SuggestionCallback callback) {
+    private record NodeResult(Node node, Chain chain, ArgumentResult<Object> argumentResult, SuggestionCallback callback) {
         public String name() {
             return node.argument().getId();
         }
@@ -372,7 +409,7 @@ final class CommandParserImpl implements CommandParser {
 
     // ARGUMENT
 
-    private static <T> ArgumentResult<T> parse(@NotNull CommandSender sender, Argument<T> argument, CommandStringReader reader) {
+    private static <T> ArgumentResult<T> parseArgument(@NotNull CommandSender sender, Argument<T> argument, CommandStringReader reader) {
         // Handle specific type without loop
         try {
             // Single word argument

src/main/java/net/minestom/server/command/GraphImpl.java

@@ -4,6 +4,8 @@ import net.minestom.server.command.builder.Command;
 import net.minestom.server.command.builder.CommandExecutor;
 import net.minestom.server.command.builder.CommandSyntax;
 import net.minestom.server.command.builder.arguments.Argument;
+import net.minestom.server.command.builder.arguments.ArgumentCommand;
+import net.minestom.server.command.builder.arguments.ArgumentLiteral;
 import net.minestom.server.command.builder.condition.CommandCondition;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -62,6 +64,12 @@ record GraphImpl(NodeImpl root) implements Graph {
     }
 
     record NodeImpl(Argument<?> argument, ExecutionImpl execution, List<Graph.Node> next) implements Graph.Node {
+        NodeImpl(Argument<?> argument, ExecutionImpl execution, List<Graph.Node> next) {
+            this.argument = argument;
+            this.execution = execution;
+            this.next = next.stream().sorted(nodePriority).toList();
+        }
+
         static NodeImpl fromBuilder(BuilderImpl builder) {
             final List<BuilderImpl> children = builder.children;
             Node[] nodes = new NodeImpl[children.size()];
@@ -76,6 +84,17 @@ record GraphImpl(NodeImpl root) implements Graph {
         static NodeImpl rootCommands(Collection<Command> commands) {
             return ConversionNode.rootConv(commands).toNode();
         }
+
+        private static final java.util.Comparator<Node> nodePriority = (node1, node2) -> {
+            int node1Value = argumentValue(node1.argument());
+            int node2Value = argumentValue(node2.argument());
+            return Integer.compare(node1Value, node2Value);
+        };
+        private static int argumentValue(Argument<?> argument) {
+            if (argument.getClass() == ArgumentCommand.class) return -3000;
+            if (argument.getClass() == ArgumentLiteral.class) return -2000;
+            return -1000;
+        }
     }
 
     record ExecutionImpl(Predicate<CommandSender> predicate,
@@ -113,8 +132,17 @@ record GraphImpl(NodeImpl root) implements Graph {
         }
     }
 
-    private record ConversionNode(Argument<?> argument, ExecutionImpl execution,
+    private static final class ConversionNode {
-                                  Map<Argument<?>, ConversionNode> nextMap) {
+        final Argument<?> argument;
+        ExecutionImpl execution;
+        final Map<Argument<?>, ConversionNode> nextMap;
+
+        public ConversionNode(Argument<?> argument, ExecutionImpl execution, Map<Argument<?>, ConversionNode> nextMap) {
+            this.argument = argument;
+            this.execution = execution;
+            this.nextMap = nextMap;
+        }
+
         ConversionNode(Argument<?> argument, ExecutionImpl execution) {
             this(argument, execution, new LinkedHashMap<>());
         }
@@ -133,10 +161,9 @@ record GraphImpl(NodeImpl root) implements Graph {
                 ConversionNode syntaxNode = root;
                 for (Argument<?> arg : syntax.getArguments()) {
                     boolean last = arg == syntax.getArguments()[syntax.getArguments().length - 1];
-                    syntaxNode = syntaxNode.nextMap.computeIfAbsent(arg, argument -> {
+                    var ex = last ? ExecutionImpl.fromSyntax(syntax) : null;
-                        var ex = last ? ExecutionImpl.fromSyntax(syntax) : null;
+                    syntaxNode = syntaxNode.nextMap.computeIfAbsent(arg, argument -> new ConversionNode(argument, ex));
-                        return new ConversionNode(argument, ex);
+                    if (syntaxNode.execution == null) syntaxNode.execution = ex;
-                    });
                 }
             }
             // Subcommands
@@ -154,6 +181,7 @@ record GraphImpl(NodeImpl root) implements Graph {
             }
             return new ConversionNode(Literal(""), null, next);
         }
+
     }
 
     static Argument<String> commandToArgument(Command command) {

src/main/java/net/minestom/server/listener/EntityActionListener.java

@@ -21,7 +21,6 @@ public class EntityActionListener {
 
     private static void setSneaking(Player player, boolean sneaking) {
         boolean oldState = player.isSneaking();
-
         player.setSneaking(sneaking);
 
         if (oldState != sneaking) {

src/test/java/net/minestom/server/command/CommandManagerTest.java

@@ -1,7 +1,10 @@
 package net.minestom.server.command;
 
 import net.minestom.server.command.builder.Command;
+import net.minestom.server.command.builder.CommandResult;
+import net.minestom.server.command.builder.arguments.ArgumentType;
 import net.minestom.server.network.packet.server.play.DeclareCommandsPacket;
+import org.jetbrains.annotations.NotNull;
 import org.junit.jupiter.api.Test;
 
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -45,6 +48,62 @@ public class CommandManagerTest {
         assertTrue(check.get());
     }
 
+    @Test
+    public void testSharedArgumentSyntaxABFirst() {
+        var manager = new CommandManager();
+
+        var checkA = new AtomicBoolean(false);
+        var checkAB = new AtomicBoolean(false);
+
+        var cmd = new Command("cmd");
+        var argA = ArgumentType.String("a");
+        var argB = ArgumentType.String("b");
+        cmd.addSyntax((sender, context) -> checkAB.set(true), argA, argB);
+        cmd.addSyntax((sender, context) -> checkA.set(true), argA);
+        manager.register(cmd);
+
+        var result = manager.executeServerCommand("cmd a");
+        assertEquals(CommandResult.Type.SUCCESS, result.getType());
+        assertTrue(checkA.get());
+        assertFalse(checkAB.get());
+
+        checkA.set(false); // these should be different tests
+        checkAB.set(false);
+
+        result = manager.executeServerCommand("cmd a b");
+        assertEquals(CommandResult.Type.SUCCESS, result.getType());
+        assertFalse(checkA.get());
+        assertTrue(checkAB.get());
+    }
+
+    @Test
+    public void testSharedArgumentSyntaxAFirst() {
+        var manager = new CommandManager();
+
+        var checkA = new AtomicBoolean(false);
+        var checkAB = new AtomicBoolean(false);
+
+        var cmd = new Command("cmd");
+        var argA = ArgumentType.String("a");
+        var argB = ArgumentType.String("b");
+        cmd.addSyntax((sender, context) -> checkA.set(true), argA);
+        cmd.addSyntax((sender, context) -> checkAB.set(true), argA, argB);
+        manager.register(cmd);
+
+        var result = manager.executeServerCommand("cmd a");
+        assertEquals(CommandResult.Type.SUCCESS, result.getType());
+        assertTrue(checkA.get());
+        assertFalse(checkAB.get());
+
+        checkA.set(false); // these should be different tests
+        checkAB.set(false);
+
+        result = manager.executeServerCommand("cmd a b");
+        assertEquals(CommandResult.Type.SUCCESS, result.getType());
+        assertFalse(checkA.get());
+        assertTrue(checkAB.get());
+    }
+
     private static void assertNodeEquals(DeclareCommandsPacket.Node node, byte flags, int[] children, int redirectedNode,
                                          String name, String parser, byte[] properties, String suggestionsType) {
         assertEquals(flags, node.flags);

src/test/java/net/minestom/server/command/CommandSuggestionIntegrationTest.java

@@ -12,6 +12,8 @@ import org.junit.jupiter.api.Test;
 import java.util.List;
 
 import static net.minestom.server.command.builder.arguments.ArgumentType.Literal;
+import static net.minestom.server.command.builder.arguments.ArgumentType.Word;
+import static net.minestom.server.command.builder.arguments.ArgumentType.Integer;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;
 
@@ -48,4 +50,29 @@ public class CommandSuggestionIntegrationTest {
             assertEquals(List.of(new TabCompletePacket.Match("test1", null)), tabCompletePacket.matches());
         });
     }
+
+    @Test
+    public void suggestionWithDefaults(Env env) {
+        var instance = env.createFlatInstance();
+        var connection = env.createConnection();
+        var player = connection.connect(instance, new Pos(0, 42, 0)).join();
+
+        var suggestArg = Word("suggestArg").setSuggestionCallback(
+                (sender, context, suggestion) -> suggestion.addEntry(new SuggestionEntry("suggestion"))
+        );
+        var defaultArg = Integer("defaultArg").setDefaultValue(123);
+
+        var command = new Command("foo");
+
+        command.addSyntax((sender,context)->{}, suggestArg, defaultArg);
+        env.process().command().register(command);
+
+        var listener = connection.trackIncoming(TabCompletePacket.class);
+        player.addPacketToQueue(new ClientTabCompletePacket(1, "foo 1"));
+        player.interpretPacketQueue();
+
+        listener.assertSingle(tabCompletePacket -> {
+            assertEquals(List.of(new TabCompletePacket.Match("suggestion", null)), tabCompletePacket.matches());
+        });
+    }
 }

src/test/java/net/minestom/server/command/CommandSyntaxMultiTest.java

@@ -7,6 +7,7 @@ import org.junit.jupiter.api.Test;
 import java.lang.String;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static net.minestom.server.command.builder.arguments.ArgumentType.Float;
@@ -27,6 +28,25 @@ public class CommandSyntaxMultiTest {
         assertSyntax(args, "float 5.5", ExpectedExecution.SECOND_SYNTAX, Map.of("float", "float", "number", 5.5f));
     }
 
+    @Test
+    public void argPriority() {
+        List<List<Argument<?>>> args = List.of(
+                List.of(Word("word")),
+                List.of(Literal("literal"))
+        );
+        assertSyntax(args, "literal", ExpectedExecution.SECOND_SYNTAX);
+    }
+
+    @Test
+    public void similarArgs() {
+        List<List<Argument<?>>> args = List.of(
+                List.of(Word("a")),
+                List.of(Word("b"), Word("a"))
+        );
+        assertSyntax(args, "baz", ExpectedExecution.FIRST_SYNTAX);
+        assertSyntax(args, "bar baz", ExpectedExecution.SECOND_SYNTAX);
+    }
+
     private static void assertSyntax(List<List<Argument<?>>> args, String input, ExpectedExecution expectedExecution, Map<String, Object> expectedValues) {
         final String commandName = "name";