Feature: Allow argument names to be inferred from parameter names

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `executeFuture` to `CommandExecutionHandler` which is now used internally. By default, this delegates to the old 
   `execute` method
 - Annotations: Apply builder modifiers from class annotations ([#303](https://github.com/Incendo/cloud/pull/303))
+- Annotations: Add default value to `@Argument`, which will force the parser to infer the argument name from the parameter name
 
 ### Fixed
 - Bukkit: Permission checking and syntax string for Bukkit '/help' command

cloud-annotations/src/main/java/cloud/commandframework/annotations/AnnotationParser.java

@@ -79,6 +79,11 @@ import java.util.function.Function;
  */
 public final class AnnotationParser<C> {
 
+    /**
+     * The value of {@link Argument} that should be used to infer argument names from parameter names.
+     */
+    public static final String INFERRED_ARGUMENT_NAME = "__INFERRED_ARGUMENT_NAME__";
+
     private final SyntaxParser syntaxParser = new SyntaxParser();
     private final ArgumentExtractor argumentExtractor = new ArgumentExtractor();
 
@@ -438,7 +443,7 @@ public final class AnnotationParser<C> {
             for (final ArgumentParameterPair argumentPair : arguments) {
                 final CommandArgument<C, ?> argument = this.buildArgument(
                         method,
-                        this.findSyntaxFragment(tokens, argumentPair.getArgument().value()),
+                        this.findSyntaxFragment(tokens, argumentPair.argumentName()),
                         argumentPair
                 );
                 commandArguments.put(argument.getName(), argument);
@@ -606,13 +611,13 @@ public final class AnnotationParser<C> {
         if (syntaxFragment == null || syntaxFragment.getArgumentMode() == ArgumentMode.LITERAL) {
             throw new IllegalArgumentException(String.format(
                     "Invalid command argument '%s' in method '%s': "
-                            + "Missing syntax mapping", argumentPair.getArgument().value(), method.getName()));
+                            + "Missing syntax mapping", argumentPair.argumentName(), method.getName()));
         }
         final Argument argument = argumentPair.getArgument();
         /* Create the argument builder */
         @SuppressWarnings("rawtypes") final CommandArgument.Builder argumentBuilder = CommandArgument.ofType(
                 parameter.getType(),
-                argument.value()
+                argumentPair.argumentName()
         );
         /* Set the argument requirement status */
         if (syntaxFragment.getArgumentMode() == ArgumentMode.OPTIONAL) {

cloud-annotations/src/main/java/cloud/commandframework/annotations/Argument.java

@@ -39,11 +39,17 @@ import java.util.function.BiFunction;
 public @interface Argument {
 
     /**
-     * Argument name
+     * The name of the argument that this parameter is bound to.
+     * This value must be overridden unless you have explicitly enabled
+     * the preservation of parameter names in your compiler options.
+     *
+     * If the parameter names are preserved and the name of the bound
+     * argument is the same as the parameter name, the default value
+     * may be used.
      *
      * @return Argument name
      */
-    @NonNull String value();
+    @NonNull String value() default AnnotationParser.INFERRED_ARGUMENT_NAME;
 
     /**
      * Name of the argument parser

cloud-annotations/src/main/java/cloud/commandframework/annotations/ArgumentParameterPair.java

@@ -48,4 +48,12 @@ final class ArgumentParameterPair {
         return this.argument;
     }
 
+    @NonNull String argumentName() {
+        if (this.argument.value().equals(AnnotationParser.INFERRED_ARGUMENT_NAME)) {
+            return this.parameter.getName();
+        } else {
+            return this.argument.value();
+        }
+    }
+
 }

cloud-annotations/src/main/java/cloud/commandframework/annotations/MethodCommandExecutionHandler.java

@@ -105,11 +105,19 @@ public class MethodCommandExecutionHandler<C> implements CommandExecutionHandler
         for (final Parameter parameter : this.parameters) {
             if (parameter.isAnnotationPresent(Argument.class)) {
                 final Argument argument = parameter.getAnnotation(Argument.class);
-                final CommandArgument<C, ?> commandArgument = this.context.commandArguments.get(argument.value());
-                if (commandArgument.isRequired()) {
-                    arguments.add(commandContext.get(argument.value()));
+
+                final String argumentName;
+                if (argument.value().equals(AnnotationParser.INFERRED_ARGUMENT_NAME)) {
+                    argumentName = parameter.getName();
                 } else {
-                    final Object optional = commandContext.getOptional(argument.value()).orElse(null);
+                    argumentName = argument.value();
+                }
+
+                final CommandArgument<C, ?> commandArgument = this.context.commandArguments.get(argumentName);
+                if (commandArgument.isRequired()) {
+                    arguments.add(commandContext.get(argumentName));
+                } else {
+                    final Object optional = commandContext.getOptional(argumentName).orElse(null);
                     arguments.add(optional);
                 }
             } else if (parameter.isAnnotationPresent(Flag.class)) {