✨ Work towards making CommandMeta typesafe (#173)

Co-authored-by: Alexander Söderberg <sauilitired@gmail.com>

CHANGELOG.md

@@ -8,10 +8,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
  - Added `@Suggestions` annotated methods
+ - Type safe meta system
 
 ### Changed
  - Moved the parser injector registry into CommandManager and added injection to CommandContext
 
+### Deprecated
+ - String keyed command meta
+
 ## [1.2.0] - 2020-12-07
 
 ### Added

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

@@ -307,7 +307,7 @@ public final class AnnotationParser<C> {
             final SimpleCommandMeta.Builder metaBuilder = SimpleCommandMeta.builder()
                     .with(this.metaFactory.apply(method));
             if (methodOrClassHasAnnotation(method, Confirmation.class)) {
-                metaBuilder.with(CommandConfirmationManager.CONFIRMATION_REQUIRED_META, "true");
+                metaBuilder.with(CommandConfirmationManager.META_CONFIRMATION_REQUIRED, true);
             }
 
             @SuppressWarnings("rawtypes")

cloud-core/src/main/java/cloud/commandframework/Command.java

@@ -269,7 +269,7 @@ public class Command<C> {
      * @return {@code true} if the command is hidden, {@code false} if not
      */
     public boolean isHidden() {
-        return this.getCommandMeta().getOrDefault("hidden", "true").equals("true");
+        return this.getCommandMeta().getOrDefault(CommandMeta.HIDDEN, false);
     }
 
 
@@ -337,7 +337,9 @@ public class Command<C> {
          * @param key   Meta key
          * @param value Meta value
          * @return New builder instance using the inserted meta key-value pair
+         * @deprecated for removal since 1.2.0, use the typesafe variant at {@link #meta(CommandMeta.Key, Object)} instead.
          */
+        @Deprecated
         public @NonNull Builder<C> meta(final @NonNull String key, final @NonNull String value) {
             final CommandMeta commandMeta = SimpleCommandMeta.builder().with(this.commandMeta).with(key, value).build();
             return new Builder<>(
@@ -351,6 +353,28 @@ public class Command<C> {
             );
         }
 
+        /**
+         * Add command meta to the internal command meta map
+         *
+         * @param <V>   Meta value type
+         * @param key   Meta key
+         * @param value Meta value
+         * @return New builder instance using the inserted meta key-value pair
+         * @since 1.3.0
+         */
+        public <V> @NonNull Builder<C> meta(final CommandMeta.@NonNull Key<V> key, final @NonNull V value) {
+            final CommandMeta commandMeta = SimpleCommandMeta.builder().with(this.commandMeta).with(key, value).build();
+            return new Builder<>(
+                    this.commandManager,
+                    commandMeta,
+                    this.senderType,
+                    this.commandArguments,
+                    this.commandExecutionHandler,
+                    this.commandPermission,
+                    this.flags
+            );
+        }
+
         /**
          * Supply a command manager instance to the builder. This will be used when attempting to
          * retrieve command argument parsers, in the case that they're needed. This
@@ -746,7 +770,7 @@ public class Command<C> {
          * @return New builder instance that indicates that the constructed command should be hidden
          */
         public @NonNull Builder<C> hidden() {
-            return this.meta("hidden", "true");
+            return this.meta(CommandMeta.HIDDEN, true);
         }
 
         /**

cloud-core/src/main/java/cloud/commandframework/CommandHelpHandler.java

@@ -25,6 +25,7 @@ package cloud.commandframework;
 
 import cloud.commandframework.arguments.CommandArgument;
 import cloud.commandframework.arguments.StaticArgument;
+import cloud.commandframework.meta.CommandMeta;
 import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
@@ -55,7 +56,7 @@ public final class CommandHelpHandler<C> {
         final List<VerboseHelpEntry<C>> syntaxHints = new ArrayList<>();
         for (final Command<C> command : this.commandManager.getCommands()) {
             final List<CommandArgument<C, ?>> arguments = command.getArguments();
-            final String description = command.getCommandMeta().getOrDefault("description", "");
+            final String description = command.getCommandMeta().getOrDefault(CommandMeta.DESCRIPTION, "");
             syntaxHints.add(new VerboseHelpEntry<>(
                     command,
                     this.commandManager.getCommandSyntaxFormatter()
@@ -163,7 +164,7 @@ public final class CommandHelpHandler<C> {
             final List<VerboseHelpEntry<C>> syntaxHints = new ArrayList<>();
             for (final Command<C> command : availableCommands) {
                 final List<CommandArgument<C, ?>> arguments = command.getArguments();
-                final String description = command.getCommandMeta().getOrDefault("description", "");
+                final String description = command.getCommandMeta().getOrDefault(CommandMeta.DESCRIPTION, "");
                 syntaxHints.add(new VerboseHelpEntry<>(
                         command,
                         this.commandManager.getCommandSyntaxFormatter()
@@ -350,8 +351,8 @@ public final class CommandHelpHandler<C> {
 
         private VerboseHelpTopic(final @NonNull Command<C> command) {
             this.command = command;
-            final String shortDescription = command.getCommandMeta().getOrDefault("description", "No description");
+            final String shortDescription = command.getCommandMeta().getOrDefault(CommandMeta.DESCRIPTION, "No description");
-            this.description = command.getCommandMeta().getOrDefault("long-description", shortDescription);
+            this.description = command.getCommandMeta().getOrDefault(CommandMeta.LONG_DESCRIPTION, shortDescription);
         }
 
         /**

cloud-core/src/main/java/cloud/commandframework/annotations/AnnotatedElementAccessor.java

@@ -43,7 +43,7 @@ final class AnnotatedElementAccessor implements AnnotationAccessor {
 
     @Override
     public <A extends Annotation> @Nullable A annotation(
-            @NonNull final Class<A> clazz
+            final @NonNull Class<A> clazz
     ) {
         try {
             return element.getAnnotation(clazz);

cloud-core/src/main/java/cloud/commandframework/annotations/AnnotationAccessor.java

@@ -87,7 +87,7 @@ public interface AnnotationAccessor {
     final class NullAnnotationAccessor implements AnnotationAccessor {
 
         @Override
-        public <A extends Annotation> @Nullable A annotation(@NonNull final Class<A> clazz) {
+        public <A extends Annotation> @Nullable A annotation(final @NonNull Class<A> clazz) {
            return null;
         }
 

cloud-core/src/main/java/cloud/commandframework/arguments/DelegatingCommandSuggestionEngine.java

@@ -63,8 +63,8 @@ public final class DelegatingCommandSuggestionEngine<C> implements CommandSugges
 
     @Override
     public @NonNull List<@NonNull String> getSuggestions(
-            @NonNull final CommandContext<C> context,
+            final @NonNull CommandContext<C> context,
-            @NonNull final String input
+            final @NonNull String input
     ) {
         final @NonNull LinkedList<@NonNull String> inputQueue = new CommandInputTokenizer(input).tokenize();
         /* Store a copy of the input queue in the context */

cloud-core/src/main/java/cloud/commandframework/arguments/parser/StandardParserRegistry.java

@@ -232,15 +232,15 @@ public final class StandardParserRegistry<C> implements ParserRegistry<C> {
 
     @Override
     public void registerSuggestionProvider(
-            @NonNull final String name,
+            final @NonNull String name,
-            @NonNull final BiFunction<@NonNull CommandContext<C>, @NonNull String, @NonNull List<String>> suggestionsProvider
+            final @NonNull BiFunction<@NonNull CommandContext<C>, @NonNull String, @NonNull List<String>> suggestionsProvider
     ) {
         this.namedSuggestionProviders.put(name.toLowerCase(Locale.ENGLISH), suggestionsProvider);
     }
 
     @Override
     public @NonNull Optional<BiFunction<@NonNull CommandContext<C>, @NonNull String, @NonNull List<String>>> getSuggestionProvider(
-            @NonNull final String name
+            final @NonNull String name
     ) {
         final BiFunction<@NonNull CommandContext<C>, @NonNull String, @NonNull List<String>> suggestionProvider =
                 this.namedSuggestionProviders.get(name.toLowerCase(Locale.ENGLISH));

cloud-core/src/main/java/cloud/commandframework/arguments/preprocessor/RegexPreprocessor.java

@@ -87,7 +87,7 @@ public final class RegexPreprocessor<C> implements BiFunction<@NonNull CommandCo
 
     @Override
     public @NonNull ArgumentParseResult<Boolean> apply(
-            @NonNull final CommandContext<C> context, @NonNull final Queue<@NonNull String> strings
+            final @NonNull CommandContext<C> context, final @NonNull Queue<@NonNull String> strings
     ) {
         final String head = strings.peek();
         if (head == null) {

cloud-core/src/main/java/cloud/commandframework/arguments/standard/EnumArgument.java

@@ -70,7 +70,7 @@ public class EnumArgument<C, E extends Enum<E>> extends CommandArgument<C, E> {
      * @return Created builder
      */
     public static <C, E extends Enum<E>> EnumArgument.@NonNull Builder<C, E> newBuilder(
-            @NonNull final Class<E> enumClass,
+            final @NonNull Class<E> enumClass,
             final @NonNull String name
     ) {
         return new EnumArgument.Builder<>(name, enumClass);

cloud-core/src/main/java/cloud/commandframework/arguments/standard/StringArrayArgument.java

@@ -107,8 +107,8 @@ public final class StringArrayArgument<C> extends CommandArgument<C, String[]> {
 
         @Override
         public @NonNull ArgumentParseResult<String @NonNull []> parse(
-                @NonNull final CommandContext<@NonNull C> commandContext,
+                final @NonNull CommandContext<@NonNull C> commandContext,
-                @NonNull final Queue<@NonNull String> inputQueue
+                final @NonNull Queue<@NonNull String> inputQueue
         ) {
             final String[] result = new String[inputQueue.size()];
             for (int i = 0; i < result.length; i++) {

cloud-core/src/main/java/cloud/commandframework/captions/SimpleCaptionRegistry.java

@@ -140,8 +140,8 @@ public class SimpleCaptionRegistry<C> implements FactoryDelegatingCaptionRegistr
 
     @Override
     public final @NonNull String getCaption(
-            @NonNull final Caption caption,
+            final @NonNull Caption caption,
-            @NonNull final C sender
+            final @NonNull C sender
     ) {
         final BiFunction<Caption, C, String> messageFactory = this.messageFactories.get(caption);
         if (messageFactory == null) {

cloud-core/src/main/java/cloud/commandframework/extra/confirmation/CommandConfirmationManager.java

@@ -27,6 +27,7 @@ import cloud.commandframework.CommandManager;
 import cloud.commandframework.execution.CommandExecutionHandler;
 import cloud.commandframework.execution.postprocessor.CommandPostprocessingContext;
 import cloud.commandframework.execution.postprocessor.CommandPostprocessor;
+import cloud.commandframework.meta.CommandMeta;
 import cloud.commandframework.meta.SimpleCommandMeta;
 import cloud.commandframework.services.types.ConsumerService;
 import cloud.commandframework.types.tuples.Pair;
@@ -54,8 +55,27 @@ public class CommandConfirmationManager<C> {
 
     /**
      * Meta data stored for commands that require confirmation
+     *
+     * @deprecated for removal since 1.3.0. Use {@link #META_CONFIRMATION_REQUIRED} instead.
      */
+    @Deprecated
     public static final String CONFIRMATION_REQUIRED_META = "__REQUIRE_CONFIRMATION__";
+
+    private static final CommandMeta.Key<String> LEGACY_CONFIRMATION_META = CommandMeta.Key.of(
+            String.class,
+            CONFIRMATION_REQUIRED_META
+    );
+
+    /**
+     * Meta data stored for commands that require confirmation
+     *
+     * @since 1.3.0
+     */
+    public static final CommandMeta.Key<Boolean> META_CONFIRMATION_REQUIRED = CommandMeta.Key.of(
+            Boolean.class,
+            "cloud:require_confirmation",
+            meta -> meta.get(LEGACY_CONFIRMATION_META).map(Boolean::valueOf).orElse(null)
+    );
     private static final int MAXIMUM_PENDING_SIZE = 100;
 
     private final Consumer<CommandPostprocessingContext<C>> notifier;
@@ -120,7 +140,7 @@ public class CommandConfirmationManager<C> {
      * @return Builder instance
      */
     public SimpleCommandMeta.@NonNull Builder decorate(final SimpleCommandMeta.@NonNull Builder builder) {
-        return builder.with(CONFIRMATION_REQUIRED_META, "true");
+        return builder.with(META_CONFIRMATION_REQUIRED, true);
     }
 
     /**
@@ -158,8 +178,7 @@ public class CommandConfirmationManager<C> {
         public void accept(final @NonNull CommandPostprocessingContext<C> context) {
             if (!context.getCommand()
                     .getCommandMeta()
-                    .getOrDefault(CONFIRMATION_REQUIRED_META, "false")
+                    .getOrDefault(META_CONFIRMATION_REQUIRED, false)) {
-                    .equals("true")) {
                 return;
             }
             /* Add it to the "queue" */

cloud-core/src/main/java/cloud/commandframework/meta/CommandMeta.java

@@ -24,10 +24,16 @@
 package cloud.commandframework.meta;
 
 import cloud.commandframework.Command;
+import io.leangen.geantyref.GenericTypeReflector;
+import io.leangen.geantyref.TypeToken;
 import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.Map;
 import java.util.Optional;
+import java.util.function.Function;
+
+import static java.util.Objects.requireNonNull;
 
 /**
  * Object that is associated with a {@link Command}.
@@ -37,6 +43,15 @@ import java.util.Optional;
  */
 public abstract class CommandMeta {
 
+    private static final Key<String> LEGACY_HIDDEN = Key.of(String.class, "hidden");
+    public static final Key<String> DESCRIPTION = Key.of(String.class, "description");
+    public static final Key<String> LONG_DESCRIPTION = Key.of(String.class, "long-description");
+    public static final Key<Boolean> HIDDEN = Key.of(
+        Boolean.class,
+        "cloud:hidden",
+        meta -> Boolean.valueOf(meta.getOrDefault(LEGACY_HIDDEN, "false"))
+    );
+
     /**
      * Create a new simple command meta builder
      *
@@ -56,7 +71,9 @@ public abstract class CommandMeta {
      *
      * @param key Key
      * @return Optional that may contain the associated value
+     * @deprecated for removal since 1.3.0, see typesafe variant at {@link #get(Key)} instead
      */
+    @Deprecated
     public abstract @NonNull Optional<String> getValue(@NonNull String key);
 
     /**
@@ -65,14 +82,157 @@ public abstract class CommandMeta {
      * @param key          Key
      * @param defaultValue Default value
      * @return Value, or default value
+     * @deprecated for removal since 1.3.0, see typesafe variant at {@link #getOrDefault(Key, Object)} instead
      */
+    @Deprecated
     public abstract @NonNull String getOrDefault(@NonNull String key, @NonNull String defaultValue);
 
+    /**
+     * Get the value associated with a key.
+     *
+     * @param <V> Value type
+     * @param key Key
+     * @return Optional that may contain the associated value
+     * @since 1.3.0
+     */
+    public abstract <V> @NonNull Optional<V> get(@NonNull Key<V> key);
+
+    /**
+     * Get the value if it exists, else return the default value.
+     *
+     * @param <V>          Value type
+     * @param key          Key
+     * @param defaultValue Default value
+     * @return Value, or default value
+     * @since 1.3.0
+     */
+    public abstract <V> @NonNull V getOrDefault(@NonNull Key<V> key, @NonNull V defaultValue);
+
     /**
      * Get a copy of the meta map
      *
      * @return Copy of meta map
+     * @deprecated for removal since 1.3.0, use {@link #getAllValues()} instead.
      */
+    @Deprecated
     public abstract @NonNull Map<@NonNull String, @NonNull String> getAll();
 
+    /**
+     * Get a copy of the meta map, without type information.
+     *
+     * @return Copy of meta map
+     * @since 1.3.0
+     */
+    public abstract @NonNull Map<@NonNull String, @NonNull ?> getAllValues();
+
+    /**
+     * A key into the metadata map.
+     *
+     * @param <V> value type
+     * @since 1.3.0
+     */
+    public interface Key<V> {
+
+        /**
+         * Create a new metadata key.
+         *
+         * @param type the value type
+         * @param key the name for the key
+         * @param <T> the value type
+         * @return a new key
+         */
+        static <T> @NonNull Key<T> of(final @NonNull Class<T> type, final @NonNull String key) {
+            if (GenericTypeReflector.isMissingTypeParameters(type)) {
+                throw new IllegalArgumentException("Raw type " + type + " is prohibited");
+            }
+
+            return new SimpleKey<>(
+                TypeToken.get(requireNonNull(type, "type")),
+                requireNonNull(key, "key"),
+                null
+            );
+        }
+
+        /**
+         * Create a new metadata key.
+         *
+         * @param type the value type
+         * @param key the name for the key
+         * @param <T> the value type
+         * @return a new key
+         */
+        static <T> @NonNull Key<T> of(final @NonNull TypeToken<T> type, final @NonNull String key) {
+            return new SimpleKey<>(
+                requireNonNull(type, "type"),
+                requireNonNull(key, "key"),
+                null
+            );
+        }
+
+        /**
+         * Create a new metadata key.
+         *
+         * @param type the value type
+         * @param key the name for the key
+         * @param fallbackDerivation A function that will be called if no value is present for the key
+         * @param <T> the value type
+         * @return a new key
+         */
+        static <T> @NonNull Key<T> of(
+                final @NonNull Class<T> type,
+                final @NonNull String key,
+                final @NonNull Function<@NonNull CommandMeta, @Nullable T> fallbackDerivation) {
+            return new SimpleKey<>(
+                    TypeToken.get(requireNonNull(type, "type")),
+                    requireNonNull(key, "key"),
+                    fallbackDerivation
+            );
+        }
+
+        /**
+         * Create a new metadata key.
+         *
+         * @param type the value type
+         * @param key the name for the key
+         * @param fallbackDerivation A function that will be called if no value is present for the key
+         * @param <T> the value type
+         * @return a new key
+         */
+        static <T> @NonNull Key<T> of(
+                final @NonNull TypeToken<T> type,
+                final @NonNull String key,
+                final @NonNull Function<@NonNull CommandMeta, @Nullable T> fallbackDerivation
+        ) {
+            return new SimpleKey<>(
+                    requireNonNull(type, "type"),
+                    requireNonNull(key, "key"),
+                    fallbackDerivation
+            );
+        }
+
+        /**
+         * Get a representation of the type of value this key holds.
+         *
+         * @return the value type
+         */
+        @NonNull TypeToken<V> getValueType();
+
+        /**
+         * Get the name of this key
+         *
+         * @return the key type
+         */
+        @NonNull String getName();
+
+        /**
+         * Get a function that can be used to compute a fallback based on existing meta.
+         *
+         * <p>This function will only be used if no value is directly for the key.</p>
+         *
+         * @return the fallback derivation
+         */
+        @Nullable Function<@NonNull CommandMeta, @Nullable V> getFallbackDerivation();
+
+    }
+
 }

cloud-core/src/main/java/cloud/commandframework/meta/SimpleCommandMeta.java

@@ -23,6 +23,7 @@
 //
 package cloud.commandframework.meta;
 
+import io.leangen.geantyref.GenericTypeReflector;
 import org.checkerframework.checker.nullness.qual.NonNull;
 
 import java.util.Collections;
@@ -30,6 +31,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 /**
  * A simple immutable string-string map containing command meta
@@ -37,12 +39,22 @@ import java.util.Optional;
 @SuppressWarnings("unused")
 public class SimpleCommandMeta extends CommandMeta {
 
-    private final Map<String, String> metaMap;
+    private final Map<String, Object> metaMap;
 
+    @Deprecated
     protected SimpleCommandMeta(final @NonNull Map<@NonNull String, @NonNull String> metaMap) {
         this.metaMap = Collections.unmodifiableMap(metaMap);
     }
 
+    protected SimpleCommandMeta(final SimpleCommandMeta source) {
+        this.metaMap = source.metaMap;
+    }
+
+    // Constructor needs an extra flag to distinguish it from the old one (for reified generics)
+    SimpleCommandMeta(final @NonNull Map<@NonNull String, @NonNull Object> metaMap, final boolean unusedMarkerForNew) {
+        this.metaMap = Collections.unmodifiableMap(metaMap);
+    }
+
     /**
      * Create a new meta builder
      *
@@ -62,35 +74,78 @@ public class SimpleCommandMeta extends CommandMeta {
     }
 
     @Override
+    @Deprecated
     public final @NonNull Optional<String> getValue(final @NonNull String key) {
-        return Optional.ofNullable(this.metaMap.get(key));
+        final Object result = this.metaMap.get(key);
+        if (result != null && !(result instanceof String)) {
+            throw new IllegalArgumentException("Key '" + key + "' has been used for a new typed command meta and contains a "
+                    + "non-string value!");
+        }
+        return Optional.ofNullable((String) result);
     }
 
     @Override
+    @Deprecated
     public final @NonNull String getOrDefault(final @NonNull String key, final @NonNull String defaultValue) {
         return this.getValue(key).orElse(defaultValue);
     }
 
     @Override
+    @SuppressWarnings("unchecked")
+    public final @NonNull <V> Optional<V> get(final @NonNull Key<V> key) {
+        final Object value = this.metaMap.get(key.getName());
+        if (value == null) {
+            // Attempt to use a fallback legacy type
+            if (key.getFallbackDerivation() != null) {
+                return Optional.ofNullable(key.getFallbackDerivation().apply(this));
+            }
+
+            return Optional.empty();
+        }
+        if (!GenericTypeReflector.isSuperType(key.getValueType().getType(), value.getClass())) {
+            throw new IllegalArgumentException("Conflicting argument types between key type of "
+                    + key.getValueType().getType() + " and value type of " + value.getClass());
+        }
+
+        return Optional.of((V) value);
+    }
+
+    @Override
+    public final <V> @NonNull V getOrDefault(final @NonNull Key<V> key, final @NonNull V defaultValue) {
+        return this.get(key).orElse(defaultValue);
+    }
+
+    @Override
+    @Deprecated
     public final @NonNull Map<@NonNull String, @NonNull String> getAll() {
+        return this.metaMap.entrySet()
+                .stream().filter(ent -> ent.getValue() instanceof String)
+                .collect(Collectors.<Map.Entry<String, Object>, String, String>toMap(
+                        Map.Entry::getKey,
+                        ent -> ent.getValue().toString()
+                ));
+    }
+
+    @Override
+    public final @NonNull Map<@NonNull String, @NonNull ?> getAllValues() {
         return new HashMap<>(this.metaMap);
     }
 
     @Override
-    public final boolean equals(final Object o) {
+    public final boolean equals(final Object other) {
-        if (this == o) {
+        if (this == other) {
             return true;
         }
-        if (o == null || getClass() != o.getClass()) {
+        if (other == null || getClass() != other.getClass()) {
             return false;
         }
-        final SimpleCommandMeta that = (SimpleCommandMeta) o;
+        final SimpleCommandMeta that = (SimpleCommandMeta) other;
-        return Objects.equals(metaMap, that.metaMap);
+        return Objects.equals(this.metaMap, that.metaMap);
     }
 
     @Override
     public final int hashCode() {
-        return Objects.hashCode(metaMap);
+        return Objects.hashCode(this.metaMap);
     }
 
     /**
@@ -98,7 +153,7 @@ public class SimpleCommandMeta extends CommandMeta {
      */
     public static final class Builder {
 
-        private final Map<String, String> map = new HashMap<>();
+        private final Map<String, Object> map = new HashMap<>();
 
         private Builder() {
         }
@@ -110,7 +165,11 @@ public class SimpleCommandMeta extends CommandMeta {
          * @return Builder instance
          */
         public @NonNull Builder with(final @NonNull CommandMeta commandMeta) {
-            commandMeta.getAll().forEach(this::with);
+            if (commandMeta instanceof SimpleCommandMeta) {
+                this.map.putAll(((SimpleCommandMeta) commandMeta).metaMap);
+            } else {
+                this.map.putAll(commandMeta.getAllValues());
+            }
             return this;
         }
 
@@ -120,7 +179,9 @@ public class SimpleCommandMeta extends CommandMeta {
          * @param key   Key
          * @param value Value
          * @return Builder instance
+         * @deprecated For removal since 1.3.0, use {@link #with(Key, Object) the typesafe alternative} instead
          */
+        @Deprecated
         public @NonNull Builder with(
                 final @NonNull String key,
                 final @NonNull String value
@@ -129,13 +190,30 @@ public class SimpleCommandMeta extends CommandMeta {
             return this;
         }
 
+        /**
+         * Store a new key-value pair in the meta map
+         *
+         * @param <V>   Value type
+         * @param key   Key
+         * @param value Value
+         * @return Builder instance
+         * @since 1.3.0
+         */
+        public <V> @NonNull Builder with(
+                final @NonNull Key<V> key,
+                final @NonNull V value
+        ) {
+           this.map.put(key.getName(), value);
+           return this;
+        }
+
         /**
          * Construct a new meta instance
          *
          * @return Meta instance
          */
         public @NonNull SimpleCommandMeta build() {
-            return new SimpleCommandMeta(this.map);
+            return new SimpleCommandMeta(this.map, false);
         }
 
     }

cloud-core/src/main/java/cloud/commandframework/meta/SimpleKey.java

@@ -0,0 +1,84 @@
+//
+// MIT License
+//
+// Copyright (c) 2020 Alexander Söderberg & Contributors
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+
+package cloud.commandframework.meta;
+
+import io.leangen.geantyref.GenericTypeReflector;
+import io.leangen.geantyref.TypeToken;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.function.Function;
+
+final class SimpleKey<V> implements CommandMeta.Key<V> {
+
+    private final @NonNull TypeToken<V> valueType;
+    private final @NonNull String name;
+    private final @Nullable Function<@NonNull CommandMeta, @Nullable V> derivationFunction;
+
+    SimpleKey(
+        final @NonNull TypeToken<V> valueType,
+        final @NonNull String name,
+        final @Nullable Function<@NonNull CommandMeta, @Nullable V> derivationFunction
+    ) {
+        this.valueType = valueType;
+        this.name = name;
+        this.derivationFunction = derivationFunction;
+    }
+
+    @Override
+    public @NonNull TypeToken<V> getValueType() {
+        return this.valueType;
+    }
+
+    @Override
+    public @NonNull String getName() {
+        return this.name;
+    }
+
+    @Override
+    public @Nullable Function<@NonNull CommandMeta, @Nullable V> getFallbackDerivation() {
+        return this.derivationFunction;
+    }
+
+    @Override
+    public boolean equals(final Object other) {
+        if (this == other) {
+            return true;
+        }
+        if (other == null || getClass() != other.getClass()) {
+            return false;
+        }
+        final SimpleKey<?> that = (SimpleKey<?>) other;
+        return this.valueType.equals(that.valueType)
+                && this.name.equals(that.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return 7 * GenericTypeReflector.hashCode(this.valueType.getAnnotatedType())
+                + 31 * this.name.hashCode();
+    }
+
+}

cloud-core/src/test/java/cloud/commandframework/CommandHelpHandlerTest.java

@@ -25,6 +25,7 @@ package cloud.commandframework;
 
 import cloud.commandframework.arguments.CommandArgument;
 import cloud.commandframework.arguments.standard.IntegerArgument;
+import cloud.commandframework.meta.CommandMeta;
 import cloud.commandframework.meta.SimpleCommandMeta;
 import cloud.commandframework.types.tuples.Pair;
 import org.junit.jupiter.api.Assertions;
@@ -43,14 +44,14 @@ class CommandHelpHandlerTest {
     @BeforeAll
     static void setup() {
         manager = new TestCommandManager();
-        final SimpleCommandMeta meta1 = SimpleCommandMeta.builder().with("description", "Command with only literals").build();
+        final SimpleCommandMeta meta1 = SimpleCommandMeta.builder().with(CommandMeta.DESCRIPTION, "Command with only literals").build();
         manager.command(manager.commandBuilder("test", meta1).literal("this").literal("thing").build());
-        final SimpleCommandMeta meta2 = SimpleCommandMeta.builder().with("description", "Command with variables").build();
+        final SimpleCommandMeta meta2 = SimpleCommandMeta.builder().with(CommandMeta.DESCRIPTION, "Command with variables").build();
         manager.command(manager.commandBuilder("test", meta2).literal("int").
                 argument(IntegerArgument.of("int"), Description.of("A number")).build());
 
         manager.command(manager.commandBuilder("vec")
-                .meta("description", "Takes in a vector")
+                .meta(CommandMeta.DESCRIPTION, "Takes in a vector")
                 .argumentPair("vec", Pair.of("x", "y"),
                         Pair.of(Double.class, Double.class), Description.of("Vector")
                 )

cloud-irc/cloud-pircbotx/src/main/java/cloud/commandframework/pircbotx/PircBotXCommandManager.java

@@ -119,8 +119,8 @@ public class PircBotXCommandManager<C> extends CommandManager<C> {
 
     @Override
     public final boolean hasPermission(
-            @NonNull final C sender,
+            final @NonNull C sender,
-            @NonNull final String permission
+            final @NonNull String permission
     ) {
         return this.permissionFunction.apply(sender, permission);
     }
@@ -140,7 +140,7 @@ public class PircBotXCommandManager<C> extends CommandManager<C> {
         return this.commandPrefix;
     }
 
-    @NonNull final Function<User, C> getUserMapper() {
+    final @NonNull Function<User, C> getUserMapper() {
         return this.userMapper;
     }
 

cloud-irc/cloud-pircbotx/src/main/java/cloud/commandframework/pircbotx/arguments/UserArgument.java

@@ -128,8 +128,8 @@ public final class UserArgument<C> extends CommandArgument<C, User> {
 
         @Override
         public @NonNull ArgumentParseResult<@NonNull User> parse(
-                @NonNull final CommandContext<@NonNull C> commandContext,
+                final @NonNull CommandContext<@NonNull C> commandContext,
-                @NonNull final Queue<@NonNull String> inputQueue
+                final @NonNull Queue<@NonNull String> inputQueue
         ) {
             final String input = inputQueue.peek();
             if (input == null) {

cloud-minecraft/cloud-bukkit/src/main/java/cloud/commandframework/bukkit/BukkitCommand.java

@@ -31,6 +31,7 @@ import cloud.commandframework.exceptions.InvalidCommandSenderException;
 import cloud.commandframework.exceptions.InvalidSyntaxException;
 import cloud.commandframework.exceptions.NoPermissionException;
 import cloud.commandframework.exceptions.NoSuchCommandException;
+import cloud.commandframework.meta.CommandMeta;
 import org.bukkit.ChatColor;
 import org.bukkit.command.CommandSender;
 import org.bukkit.command.PluginIdentifiableCommand;
@@ -63,7 +64,7 @@ final class BukkitCommand<C> extends org.bukkit.command.Command implements Plugi
     ) {
         super(
                 label,
-                cloudCommand.getCommandMeta().getOrDefault("description", ""),
+                cloudCommand.getCommandMeta().getOrDefault(CommandMeta.DESCRIPTION, ""),
                 "",
                 aliases
         );
@@ -163,7 +164,7 @@ final class BukkitCommand<C> extends org.bukkit.command.Command implements Plugi
 
     @Override
     public String getDescription() {
-        return this.cloudCommand.getCommandMeta().getOrDefault("description", "");
+        return this.cloudCommand.getCommandMeta().getOrDefault(CommandMeta.DESCRIPTION, "");
     }
 
     @Override

cloud-minecraft/cloud-bukkit/src/main/java/cloud/commandframework/bukkit/BukkitCommandManager.java

@@ -215,6 +215,7 @@ public class BukkitCommandManager<C> extends CommandManager<C> implements Brigad
      * @return Meta data
      */
     @Override
+    @SuppressWarnings("deprecation")
     public @NonNull BukkitCommandMeta createDefaultCommandMeta() {
         return BukkitCommandMetaBuilder.builder().withDescription("").build();
     }

cloud-minecraft/cloud-bukkit/src/main/java/cloud/commandframework/bukkit/BukkitCommandMeta.java

@@ -26,6 +26,12 @@ package cloud.commandframework.bukkit;
 import cloud.commandframework.meta.SimpleCommandMeta;
 import org.checkerframework.checker.nullness.qual.NonNull;
 
+/**
+ * Bukkit-specific command metadata holder.
+ *
+ * @deprecated for removal since 1.3.0. Use the standard {@link SimpleCommandMeta instead}.
+ */
+@Deprecated
 public class BukkitCommandMeta extends SimpleCommandMeta {
 
     /**
@@ -34,7 +40,7 @@ public class BukkitCommandMeta extends SimpleCommandMeta {
      * @param simpleCommandMeta Simple command meta data instance that gets mirrored
      */
     public BukkitCommandMeta(final @NonNull SimpleCommandMeta simpleCommandMeta) {
-        super(simpleCommandMeta.getAll());
+        super(simpleCommandMeta);
     }
 
 }

cloud-minecraft/cloud-bukkit/src/main/java/cloud/commandframework/bukkit/BukkitCommandMetaBuilder.java

@@ -24,8 +24,15 @@
 package cloud.commandframework.bukkit;
 
 import cloud.commandframework.meta.CommandMeta;
+import cloud.commandframework.meta.SimpleCommandMeta;
 import org.checkerframework.checker.nullness.qual.NonNull;
 
+/**
+ * Command meta builder with bukkit-specific parameters.
+ *
+ * @deprecated for removal since 1.3.0, use plain {@link SimpleCommandMeta.Builder} instead.
+ */
+@Deprecated
 public final class BukkitCommandMetaBuilder {
 
     private BukkitCommandMetaBuilder() {
@@ -73,7 +80,7 @@ public final class BukkitCommandMetaBuilder {
          * @return Meta instance
          */
         public @NonNull BukkitCommandMeta build() {
-            return new BukkitCommandMeta(CommandMeta.simple().with("description", this.description).build());
+            return new BukkitCommandMeta(CommandMeta.simple().with(CommandMeta.DESCRIPTION, this.description).build());
         }
 
     }

cloud-minecraft/cloud-bungee/src/main/java/cloud/commandframework/bungee/arguments/PlayerArgument.java

@@ -139,8 +139,8 @@ public final class PlayerArgument<C> extends CommandArgument<C, ProxiedPlayer> {
 
         @Override
         public @NonNull ArgumentParseResult<@NonNull ProxiedPlayer> parse(
-                @NonNull final CommandContext<@NonNull C> commandContext,
+                final @NonNull CommandContext<@NonNull C> commandContext,
-                @NonNull final Queue<@NonNull String> inputQueue
+                final @NonNull Queue<@NonNull String> inputQueue
         ) {
             final String input = inputQueue.peek();
             if (input == null) {

cloud-minecraft/cloud-bungee/src/main/java/cloud/commandframework/bungee/arguments/ServerArgument.java

@@ -137,8 +137,8 @@ public final class ServerArgument<C> extends CommandArgument<C, ServerInfo> {
 
         @Override
         public @NonNull ArgumentParseResult<@NonNull ServerInfo> parse(
-                @NonNull final CommandContext<@NonNull C> commandContext,
+                final @NonNull CommandContext<@NonNull C> commandContext,
-                @NonNull final Queue<@NonNull String> inputQueue
+                final @NonNull Queue<@NonNull String> inputQueue
         ) {
             final String input = inputQueue.peek();
             if (input == null) {

cloud-minecraft/cloud-cloudburst/src/main/java/cloud/commandframework/cloudburst/CloudburstCommand.java

@@ -31,6 +31,7 @@ import cloud.commandframework.exceptions.InvalidCommandSenderException;
 import cloud.commandframework.exceptions.InvalidSyntaxException;
 import cloud.commandframework.exceptions.NoPermissionException;
 import cloud.commandframework.exceptions.NoSuchCommandException;
+import cloud.commandframework.meta.CommandMeta;
 import org.checkerframework.checker.nullness.qual.NonNull;
 import org.cloudburstmc.server.command.CommandSender;
 import org.cloudburstmc.server.command.PluginCommand;
@@ -61,7 +62,7 @@ final class CloudburstCommand<C> extends PluginCommand<Plugin> {
         super(manager.getOwningPlugin(), CommandData.builder(label)
                 .addAliases(aliases.toArray(new String[0]))
                 .addPermission(cloudCommand.getCommandPermission().toString())
-                .setDescription(cloudCommand.getCommandMeta().getOrDefault("description", ""))
+                .setDescription(cloudCommand.getCommandMeta().getOrDefault(CommandMeta.DESCRIPTION, ""))
                 .build());
         this.command = command;
         this.manager = manager;

cloud-minecraft/cloud-velocity/src/main/java/cloud/commandframework/velocity/arguments/PlayerArgument.java

@@ -137,8 +137,8 @@ public final class PlayerArgument<C> extends CommandArgument<C, Player> {
 
         @Override
         public @NonNull ArgumentParseResult<@NonNull Player> parse(
-                @NonNull final CommandContext<@NonNull C> commandContext,
+                final @NonNull CommandContext<@NonNull C> commandContext,
-                @NonNull final Queue<@NonNull String> inputQueue
+                final @NonNull Queue<@NonNull String> inputQueue
         ) {
             final String input = inputQueue.peek();
             if (input == null) {

cloud-minecraft/cloud-velocity/src/main/java/cloud/commandframework/velocity/arguments/ServerArgument.java

@@ -133,8 +133,8 @@ public final class ServerArgument<C> extends CommandArgument<C, RegisteredServer
 
         @Override
         public @NonNull ArgumentParseResult<@NonNull RegisteredServer> parse(
-                @NonNull final CommandContext<@NonNull C> commandContext,
+                final @NonNull CommandContext<@NonNull C> commandContext,
-                @NonNull final Queue<@NonNull String> inputQueue
+                final @NonNull Queue<@NonNull String> inputQueue
         ) {
             final String input = inputQueue.peek();
             if (input == null) {

examples/example-bukkit/src/main/java/cloud/commandframework/examples/bukkit/ExamplePlugin.java

@@ -44,7 +44,6 @@ import cloud.commandframework.arguments.standard.EnumArgument;
 import cloud.commandframework.arguments.standard.IntegerArgument;
 import cloud.commandframework.arguments.standard.StringArrayArgument;
 import cloud.commandframework.bukkit.BukkitCommandManager;
-import cloud.commandframework.bukkit.BukkitCommandMetaBuilder;
 import cloud.commandframework.bukkit.CloudBukkitCapabilities;
 import cloud.commandframework.bukkit.arguments.selector.SingleEntitySelector;
 import cloud.commandframework.bukkit.parsers.EnchantmentArgument;
@@ -178,9 +177,9 @@ public final class ExamplePlugin extends JavaPlugin {
         // @CommandMethod
         //
         final Function<ParserParameters, CommandMeta> commandMetaFunction = p ->
-                BukkitCommandMetaBuilder.builder()
+                CommandMeta.simple()
                         // This will allow you to decorate commands with descriptions
-                        .withDescription(p.get(StandardParameters.DESCRIPTION, "No description"))
+                        .with(CommandMeta.DESCRIPTION, p.get(StandardParameters.DESCRIPTION, "No description"))
                         .build();
         this.annotationParser = new AnnotationParser<>(
                 /* Manager */ this.manager,

examples/example-javacord/src/main/java/cloud/commandframework/examples/javacord/ExampleBot.java

@@ -50,7 +50,7 @@ public final class ExampleBot {
      *
      * @param args Arguments to start the bot with (NOT used)
      */
-    public static void main(@NonNull final String[] args) {
+    public static void main(final @NonNull String[] args) {
         SimplixInstaller
                 .instance()
                 .register(ExampleBot.class);

examples/example-javacord/src/main/java/cloud/commandframework/examples/javacord/application/ExampleApplication.java

@@ -56,9 +56,9 @@ public class ExampleApplication {
      */
     @Inject
     public ExampleApplication(
-            @NonNull final DiscordApiComponent discordApiComponent,
+            final @NonNull DiscordApiComponent discordApiComponent,
-            @NonNull final CommandsComponent commandsComponent,
+            final @NonNull CommandsComponent commandsComponent,
-            @NonNull final ScheduledExecutorService executorService
+            final @NonNull ScheduledExecutorService executorService
     ) throws
             Exception {
         this.discordApiComponent = discordApiComponent;

examples/example-javacord/src/main/java/cloud/commandframework/examples/javacord/components/CommandsComponent.java

@@ -53,7 +53,7 @@ public class CommandsComponent {
      * @param discordApiComponent Instance of the {@link DiscordApiComponent} for registering the command listener
      */
     @Inject
-    public CommandsComponent(@NonNull final DiscordApiComponent discordApiComponent) {
+    public CommandsComponent(final @NonNull DiscordApiComponent discordApiComponent) {
         this.discordApiComponent = discordApiComponent;
     }
 

examples/example-javacord/src/main/java/cloud/commandframework/examples/javacord/components/DiscordApiComponent.java

@@ -55,7 +55,7 @@ public class DiscordApiComponent {
      *
      * @param token The Discord Bot token
      */
-    public final void login(@NonNull final String token) {
+    public final void login(final @NonNull String token) {
         LOG.info("Logging in to Discord...");
 
         this.api = this.builder.setToken(token).login().join();