#1497 Show specific message for invalid YAML files (#1506)

* #1497 Throw dedicated exception for invalid YAML files and handle it on startup
- Wrap SnakeYAML exceptions when loading config.yml and commands.yml on startup into own exception type
- Handle exception type on startup with specific error message

* #1497 Fix inaccurate JavaDoc comment

src/main/java/fr/xephi/authme/AuthMe.java

@@ -26,11 +26,13 @@ import fr.xephi.authme.service.BackupService;
 import fr.xephi.authme.service.BukkitService;
 import fr.xephi.authme.service.MigrationService;
 import fr.xephi.authme.service.bungeecord.BungeeReceiver;
+import fr.xephi.authme.service.yaml.YamlParseException;
 import fr.xephi.authme.settings.Settings;
 import fr.xephi.authme.settings.SettingsWarner;
 import fr.xephi.authme.settings.properties.SecuritySettings;
 import fr.xephi.authme.task.CleanupTask;
 import fr.xephi.authme.task.purge.PurgeService;
+import fr.xephi.authme.util.ExceptionUtils;
 import org.apache.commons.lang.SystemUtils;
 import org.bukkit.Server;
 import org.bukkit.command.Command;
@@ -133,7 +135,13 @@ public class AuthMe extends JavaPlugin {
         try {
             initialize();
         } catch (Throwable th) {
-            ConsoleLogger.logException("Aborting initialization of AuthMe:", th);
+            YamlParseException yamlParseException = ExceptionUtils.findThrowableInCause(YamlParseException.class, th);
+            if (yamlParseException == null) {
+                ConsoleLogger.logException("Aborting initialization of AuthMe:", th);
+            } else {
+                ConsoleLogger.logException("File '" + yamlParseException.getFile() + "' contains invalid YAML. "
+                    + "Please run its contents through http://yamllint.com", yamlParseException);
+            }
             stopOrUnload();
             return;
         }

src/main/java/fr/xephi/authme/initialization/SettingsProvider.java

@@ -2,7 +2,7 @@ package fr.xephi.authme.initialization;
 
 import ch.jalu.configme.configurationdata.ConfigurationData;
 import ch.jalu.configme.resource.PropertyResource;
-import ch.jalu.configme.resource.YamlFileResource;
+import fr.xephi.authme.service.yaml.YamlFileResourceProvider;
 import fr.xephi.authme.settings.Settings;
 import fr.xephi.authme.settings.SettingsMigrationService;
 import fr.xephi.authme.settings.properties.AuthMeSettingsRetriever;
@@ -37,7 +37,7 @@ public class SettingsProvider implements Provider<Settings> {
         if (!configFile.exists()) {
             FileUtils.create(configFile);
         }
-        PropertyResource resource = new YamlFileResource(configFile);
+        PropertyResource resource = YamlFileResourceProvider.loadFromFile(configFile);
         ConfigurationData configurationData = AuthMeSettingsRetriever.buildConfigurationData();
         return new Settings(dataFolder, resource, migrationService, configurationData);
     }

src/main/java/fr/xephi/authme/service/yaml/YamlFileResourceProvider.java

@@ -0,0 +1,30 @@
+package fr.xephi.authme.service.yaml;
+
+import ch.jalu.configme.resource.YamlFileResource;
+import org.yaml.snakeyaml.parser.ParserException;
+
+import java.io.File;
+
+/**
+ * Creates {@link YamlFileResource} objects.
+ */
+public final class YamlFileResourceProvider {
+
+    private YamlFileResourceProvider() {
+    }
+
+    /**
+     * Creates a {@link YamlFileResource} instance for the given file. Wraps SnakeYAML's parse exception
+     * into an AuthMe exception.
+     *
+     * @param file the file to load
+     * @return the generated resource
+     */
+    public static YamlFileResource loadFromFile(File file) {
+        try {
+            return new YamlFileResource(file);
+        } catch (ParserException e) {
+            throw new YamlParseException(file.getPath(), e);
+        }
+    }
+}

src/main/java/fr/xephi/authme/service/yaml/YamlParseException.java

@@ -0,0 +1,26 @@
+package fr.xephi.authme.service.yaml;
+
+import org.yaml.snakeyaml.parser.ParserException;
+
+/**
+ * Exception when a YAML file could not be parsed.
+ */
+public class YamlParseException extends RuntimeException {
+
+    private final String file;
+
+    /**
+     * Constructor.
+     *
+     * @param file the file a parsing exception occurred with
+     * @param snakeYamlException the caught exception from SnakeYAML
+     */
+    public YamlParseException(String file, ParserException snakeYamlException) {
+        super(snakeYamlException);
+        this.file = file;
+    }
+
+    public String getFile() {
+        return file;
+    }
+}

src/main/java/fr/xephi/authme/settings/commandconfig/CommandManager.java

@@ -1,11 +1,11 @@
 package fr.xephi.authme.settings.commandconfig;
 
 import ch.jalu.configme.SettingsManager;
-import ch.jalu.configme.resource.YamlFileResource;
 import fr.xephi.authme.initialization.DataFolder;
 import fr.xephi.authme.initialization.Reloadable;
 import fr.xephi.authme.service.BukkitService;
 import fr.xephi.authme.service.GeoIpService;
+import fr.xephi.authme.service.yaml.YamlFileResourceProvider;
 import fr.xephi.authme.util.FileUtils;
 import fr.xephi.authme.util.PlayerUtils;
 import fr.xephi.authme.util.lazytags.Tag;
@@ -149,7 +149,7 @@ public class CommandManager implements Reloadable {
         FileUtils.copyFileFromResource(file, "commands.yml");
 
         SettingsManager settingsManager = new SettingsManager(
-            new YamlFileResource(file), commandMigrationService, CommandSettingsHolder.class);
+            YamlFileResourceProvider.loadFromFile(file), commandMigrationService, CommandSettingsHolder.class);
         CommandConfig commandConfig = settingsManager.getProperty(CommandSettingsHolder.COMMANDS);
         onJoinCommands = newReplacer(commandConfig.getOnJoin());
         onLoginCommands = newOnLoginCmdReplacer(commandConfig.getOnLogin());

src/main/java/fr/xephi/authme/util/ExceptionUtils.java

@@ -0,0 +1,36 @@
+package fr.xephi.authme.util;
+
+import com.google.common.collect.Sets;
+
+import java.util.Set;
+
+/**
+ * Utilities for exceptions.
+ */
+public final class ExceptionUtils {
+
+    private ExceptionUtils() {
+    }
+
+    /**
+     * Returns the first throwable of the given {@code wantedThrowableType} by visiting the provided
+     * throwable and its causes recursively.
+     *
+     * @param wantedThrowableType the throwable type to find
+     * @param throwable the throwable to start with
+     * @param <T> the desired throwable subtype
+     * @return the first throwable found of the given type, or null if none found
+     */
+    public static <T extends Throwable> T findThrowableInCause(Class<T> wantedThrowableType, Throwable throwable) {
+        Set<Throwable> visitedObjects = Sets.newIdentityHashSet();
+        Throwable currentThrowable = throwable;
+        while (currentThrowable != null && !visitedObjects.contains(currentThrowable)) {
+            if (wantedThrowableType.isInstance(currentThrowable)) {
+                return wantedThrowableType.cast(currentThrowable);
+            }
+            visitedObjects.add(currentThrowable);
+            currentThrowable = currentThrowable.getCause();
+        }
+        return null;
+    }
+}