Define dependency on Vault during enable (#1959)

bukkit/build.gradle

@@ -10,7 +10,7 @@ repositories {
 dependencies {
     compile project(':common')
 
-    compileOnly 'com.destroystokyo.paper:paper-api:1.15.1-R0.1-SNAPSHOT'
+    compileOnly 'com.destroystokyo.paper:paper-api:1.15.2-R0.1-SNAPSHOT'
     compileOnly 'net.kyori:text-adapter-bukkit:3.0.3'
     compileOnly 'me.lucko:commodore:1.7'
     compileOnly('net.milkbowl.vault:VaultAPI:1.6') {

bukkit/src/main/java/me/lucko/luckperms/bukkit/LPBukkitPlugin.java

@@ -43,6 +43,7 @@ import me.lucko.luckperms.bukkit.listeners.BukkitCommandListUpdater;
 import me.lucko.luckperms.bukkit.listeners.BukkitConnectionListener;
 import me.lucko.luckperms.bukkit.listeners.BukkitPlatformListener;
 import me.lucko.luckperms.bukkit.messaging.BukkitMessagingFactory;
+import me.lucko.luckperms.bukkit.util.PluginManagerUtil;
 import me.lucko.luckperms.bukkit.vault.VaultHookManager;
 import me.lucko.luckperms.common.api.LuckPermsApiProvider;
 import me.lucko.luckperms.common.calculator.CalculatorFactory;
@@ -205,6 +206,20 @@ public class LPBukkitPlugin extends AbstractLuckPermsPlugin {
             this.bootstrap.getServer().getScheduler().runTaskLaterAsynchronously(this.bootstrap, injector, 1);
         }
 
+        /*
+         * This is an unfortunate solution to a problem which shouldn't even exist. As of Spigot 1.15,
+         * the way LP establishes it's load order relative to Vault triggers a dependency warning.
+         * This is a workaround to prevent that from showing, since at the moment, there is nothing I
+         * can reasonably do to improve this handling in LP without breaking plugins which use/obtain
+         * Vault in their onEnable without depending on us.
+         *
+         * Noteworthy discussion here:
+         * - https://github.com/lucko/LuckPerms/issues/1959
+         * - https://hub.spigotmc.org/jira/browse/SPIGOT-5546
+         * - https://github.com/PaperMC/Paper/pull/3509
+         */
+        PluginManagerUtil.injectDependency(this.bootstrap.getServer().getPluginManager(), this.bootstrap.getName(), "Vault");
+
         // Provide vault support
         tryVaultHook(false);
     }

bukkit/src/main/java/me/lucko/luckperms/bukkit/util/PluginManagerUtil.java

@@ -0,0 +1,71 @@
+/*
+ * This file is part of LuckPerms, licensed under the MIT License.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) 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 me.lucko.luckperms.bukkit.util;
+
+import com.google.common.graph.MutableGraph;
+
+import org.bukkit.plugin.PluginManager;
+import org.bukkit.plugin.SimplePluginManager;
+
+import java.lang.reflect.Field;
+
+public final class PluginManagerUtil {
+    private PluginManagerUtil() {}
+
+    private static final Field DEPENDENCY_GRAPH_FIELD;
+
+    static {
+        Field dependencyGraphField = null;
+        try {
+            dependencyGraphField = SimplePluginManager.class.getDeclaredField("dependencyGraph");
+            dependencyGraphField.setAccessible(true);
+        } catch (Exception e) {
+            // ignore
+        }
+        DEPENDENCY_GRAPH_FIELD = dependencyGraphField;
+    }
+
+    /**
+     * Injects a dependency relationship into the plugin manager.
+     *
+     * @param plugin the plugin
+     * @param depend the plugin being depended on
+     */
+    @SuppressWarnings("unchecked")
+    public static void injectDependency(PluginManager pluginManager, String plugin, String depend) {
+        if (DEPENDENCY_GRAPH_FIELD == null || !(pluginManager instanceof SimplePluginManager)) {
+            return; // fail silently
+        }
+
+        try {
+            MutableGraph<String> graph = (MutableGraph<String>) DEPENDENCY_GRAPH_FIELD.get(pluginManager);
+            graph.putEdge(plugin, depend);
+        } catch (Exception e) {
+            // ignore
+        }
+    }
+
+}