#474: Add ability to set other plugin names as provided API so others can still depend on it

By: Phoenix616 <mail@moep.tv>

paper-api/src/main/java/org/bukkit/command/defaults/PluginsCommand.java

@@ -45,6 +45,10 @@ public class PluginsCommand extends BukkitCommand {
 
             pluginList.append(plugin.isEnabled() ? ChatColor.GREEN : ChatColor.RED);
             pluginList.append(plugin.getDescription().getName());
+
+            if (plugin.getDescription().getProvides().size() > 0) {
+                pluginList.append(" (").append(String.join(", ", plugin.getDescription().getProvides())).append(")");
+            }
         }
 
         return "(" + plugins.length + "): " + pluginList.toString();

paper-api/src/main/java/org/bukkit/plugin/PluginDescriptionFile.java

@@ -64,6 +64,10 @@ import org.yaml.snakeyaml.nodes.Tag;
  *     <td>{@link #getName()}</td>
  *     <td>The unique name of plugin</td>
  * </tr><tr>
+ *     <td><code>provides</code></td>
+ *     <td>{@link #getProvides()}</td>
+ *     <td>The plugin APIs which this plugin provides</td>
+ * </tr><tr>
  *     <td><code>version</code></td>
  *     <td>{@link #getVersion()}</td>
  *     <td>A plugin revision identifier</td>
@@ -130,6 +134,7 @@ import org.yaml.snakeyaml.nodes.Tag;
  * <p>
  * A plugin.yml example:<blockquote><pre>
  *name: Inferno
+ *provides: [Hell]
  *version: 1.4.1
  *description: This plugin is so 31337. You can set yourself on fire.
  *# We could place every author in the authors list, but chose not to for illustrative purposes
@@ -218,6 +223,7 @@ public final class PluginDescriptionFile {
     };
     String rawName = null;
     private String name = null;
+    private List<String> provides = ImmutableList.of();
     private String main = null;
     private String classLoaderOf = null;
     private List<String> depend = ImmutableList.of();
@@ -299,6 +305,37 @@ public final class PluginDescriptionFile {
         return name;
     }
 
+    /**
+     * Gives the list of other plugin APIs which this plugin provides.
+     * These are usable for other plugins to depend on.
+     * <ul>
+     * <li>Must consist of all alphanumeric characters, underscores, hyphon,
+     *     and period (a-z,A-Z,0-9, _.-). Any other character will cause the
+     *     plugin.yml to fail loading.
+     * <li>A different plugin providing the same one or using it as their name
+     *     will not result in the plugin to fail loading.
+     * <li>Case sensitive.
+     * <li>An entry of this list can be referenced in {@link #getDepend()},
+     *    {@link #getSoftDepend()}, and {@link #getLoadBefore()}.
+     * <li><code>provides</code> must be in <a
+     *     href="http://en.wikipedia.org/wiki/YAML#Lists">YAML list
+     *     format</a>.
+     * </ul>
+     * <p>
+     * In the plugin.yml, this entry is named <code>provides</code>.
+     * <p>
+     * Example:
+     * <blockquote><pre>provides:
+     *- OtherPluginName
+     *- OldPluginName</pre></blockquote>
+     *
+     * @return immutable list of the plugin APIs which this plugin provides
+     */
+    @NotNull
+    public List<String> getProvides() {
+        return provides;
+    }
+
     /**
      * Gives the version of the plugin.
      * <ul>
@@ -459,7 +496,7 @@ public final class PluginDescriptionFile {
      *     plugin in the <a
      *     href=https://en.wikipedia.org/wiki/Circular_dependency>network</a>,
      *     all plugins in that network will fail.
-     * <li><code>depend</code> must be in must be in <a
+     * <li><code>depend</code> must be in <a
      *     href="http://en.wikipedia.org/wiki/YAML#Lists">YAML list
      *     format</a>.
      * </ul>
@@ -923,6 +960,8 @@ public final class PluginDescriptionFile {
             throw new InvalidDescriptionException(ex, "name is of wrong type");
         }
 
+        provides = makePluginNameList(map, "provides");
+
         try {
             version = map.get("version").toString();
         } catch (NullPointerException ex) {
@@ -1080,6 +1119,9 @@ public final class PluginDescriptionFile {
         Map<String, Object> map = new HashMap<String, Object>();
 
         map.put("name", name);
+        if (provides != null) {
+            map.put("provides", provides);
+        }
         map.put("main", main);
         map.put("version", version);
         map.put("order", order.toString());

paper-api/src/main/java/org/bukkit/plugin/SimplePluginManager.java

@@ -123,6 +123,7 @@ public final class SimplePluginManager implements PluginManager {
 
         Map<String, File> plugins = new HashMap<String, File>();
         Set<String> loadedPlugins = new HashSet<String>();
+        Map<String, String> pluginsProvided = new HashMap<>();
         Map<String, Collection<String>> dependencies = new HashMap<String, Collection<String>>();
         Map<String, Collection<String>> softDependencies = new HashMap<String, Collection<String>>();
 
@@ -165,6 +166,38 @@ public final class SimplePluginManager implements PluginManager {
                 ));
             }
 
+            String removedProvided = pluginsProvided.remove(description.getName());
+            if (removedProvided != null) {
+                server.getLogger().warning(String.format(
+                        "Ambiguous plugin name `%s'. It is also provided by `%s'",
+                        description.getName(),
+                        removedProvided
+                ));
+            }
+
+            for (String provided : description.getProvides()) {
+                File pluginFile = plugins.get(provided);
+                if (pluginFile != null) {
+                    server.getLogger().warning(String.format(
+                            "`%s provides `%s' while this is also the name of `%s' in `%s'",
+                            file.getPath(),
+                            provided,
+                            pluginFile.getPath(),
+                            directory.getPath()
+                    ));
+                } else {
+                    String replacedPlugin = pluginsProvided.put(provided, description.getName());
+                    if (replacedPlugin != null) {
+                        server.getLogger().warning(String.format(
+                                "`%s' is provided by both `%s' and `%s'",
+                                provided,
+                                description.getName(),
+                                replacedPlugin
+                        ));
+                    }
+                }
+            }
+
             Collection<String> softDependencySet = description.getSoftDepend();
             if (softDependencySet != null && !softDependencySet.isEmpty()) {
                 if (softDependencies.containsKey(description.getName())) {
@@ -224,7 +257,7 @@ public final class SimplePluginManager implements PluginManager {
                             dependencyIterator.remove();
 
                         // We have a dependency not found
-                        } else if (!plugins.containsKey(dependency)) {
+                        } else if (!plugins.containsKey(dependency) && !pluginsProvided.containsKey(dependency)) {
                             missingDependency = false;
                             pluginIterator.remove();
                             softDependencies.remove(plugin);
@@ -249,7 +282,7 @@ public final class SimplePluginManager implements PluginManager {
                         String softDependency = softDependencyIterator.next();
 
                         // Soft depend is no longer around
-                        if (!plugins.containsKey(softDependency)) {
+                        if (!plugins.containsKey(softDependency) && !pluginsProvided.containsKey(softDependency)) {
                             softDependencyIterator.remove();
                         }
                     }
@@ -265,8 +298,14 @@ public final class SimplePluginManager implements PluginManager {
                     missingDependency = false;
 
                     try {
-                        result.add(loadPlugin(file));
+                        Plugin loadedPlugin = loadPlugin(file);
-                        loadedPlugins.add(plugin);
+                        if (loadedPlugin != null) {
+                            result.add(loadedPlugin);
+                            loadedPlugins.add(loadedPlugin.getName());
+                            loadedPlugins.addAll(loadedPlugin.getDescription().getProvides());
+                        } else {
+                            server.getLogger().log(Level.SEVERE, "Could not load '" + file.getPath() + "' in folder '" + directory.getPath() + "'");
+                        }
                         continue;
                     } catch (InvalidPluginException ex) {
                         server.getLogger().log(Level.SEVERE, "Could not load '" + file.getPath() + "' in folder '" + directory.getPath() + "'", ex);
@@ -290,8 +329,14 @@ public final class SimplePluginManager implements PluginManager {
                         pluginIterator.remove();
 
                         try {
-                            result.add(loadPlugin(file));
+                            Plugin loadedPlugin = loadPlugin(file);
-                            loadedPlugins.add(plugin);
+                            if (loadedPlugin != null) {
+                                result.add(loadedPlugin);
+                                loadedPlugins.add(loadedPlugin.getName());
+                                loadedPlugins.addAll(loadedPlugin.getDescription().getProvides());
+                            } else {
+                                server.getLogger().log(Level.SEVERE, "Could not load '" + file.getPath() + "' in folder '" + directory.getPath() + "'");
+                            }
                             break;
                         } catch (InvalidPluginException ex) {
                             server.getLogger().log(Level.SEVERE, "Could not load '" + file.getPath() + "' in folder '" + directory.getPath() + "'", ex);
@@ -352,6 +397,9 @@ public final class SimplePluginManager implements PluginManager {
         if (result != null) {
             plugins.add(result);
             lookupNames.put(result.getDescription().getName(), result);
+            for (String provided : result.getDescription().getProvides()) {
+                lookupNames.putIfAbsent(provided, result);
+            }
         }
 
         return result;
@@ -796,7 +844,17 @@ public final class SimplePluginManager implements PluginManager {
         Preconditions.checkArgument(plugin != null, "plugin");
         Preconditions.checkArgument(depend != null, "depend");
 
-        return dependencyGraph.nodes().contains(plugin.getName()) && Graphs.reachableNodes(dependencyGraph, plugin.getName()).contains(depend.getName());
+        if (dependencyGraph.nodes().contains(plugin.getName())) {
+            if (Graphs.reachableNodes(dependencyGraph, plugin.getName()).contains(depend.getName())) {
+                return true;
+            }
+            for (String provided : depend.getProvides()) {
+                if (Graphs.reachableNodes(dependencyGraph, plugin.getName()).contains(provided)) {
+                    return true;
+                }
+            }
+        }
+        return false;
     }
 
     @Override