Detect failed legacy plugin conversions on Bukkit

lang/en.json

@@ -74,6 +74,7 @@
   "mod-incompatible-problem": "The mods '{{first-mod-name}}' and '{{second-mod-name}}' are incompatible.",
   "server-install-different-version-solution": "Install the version '{{software-version}}' of your server software.",
   "plugin-api-version-problem": "The plugin '{{plugin-name}}' needs version '{{software-version}}' of your server software.",
+  "legacy-plugin-conversion-problem": "The legacy plugin '{{plugin-name}}' could not be converted for this server version.",
   "plugin-java-version-problem": "The plugin '{{plugin-name}}' requires Java version {{java-version}} or later to run.",
   "change-java-version-solution": "Change your Java version to {{java-version}} or later.",
   "ticking-entity-problem": "The entity '{{name}}' at the location {{location}} is causing issues while ticking.",

src/Analyser/BukkitAnalyser.php

@@ -5,6 +5,7 @@
 use Aternos\Codex\Analysis\PatternInsightInterface;
 use Aternos\Codex\Minecraft\Analysis\Problem\Bukkit\AmbiguousPluginNameProblem;
 use Aternos\Codex\Minecraft\Analysis\Problem\Bukkit\ChunkLoadExceptionProblem;
+use Aternos\Codex\Minecraft\Analysis\Problem\Bukkit\LegacyPluginConversionProblem;
 use Aternos\Codex\Minecraft\Analysis\Problem\Bukkit\Plugin\AuthMeShutdownProblem;
 use Aternos\Codex\Minecraft\Analysis\Problem\Bukkit\Plugin\MultiverseLoadProblem;
 use Aternos\Codex\Minecraft\Analysis\Problem\Bukkit\Plugin\PermissionsExConfigProblem;
@@ -42,6 +43,7 @@ public static function getInsightClasses(): array
             PluginDependenciesProblem::class,
             UnsupportedApiVersionProblem::class,
             UnsupportedClassVersionProblem::class,
+            LegacyPluginConversionProblem::class,
         ];
     }
 

src/Analysis/Problem/Bukkit/LegacyPluginConversionProblem.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Aternos\Codex\Minecraft\Analysis\Problem\Bukkit;
+
+use Aternos\Codex\Minecraft\Translator\Translator;
+
+/**
+ * CraftBukkit could not convert a class of a legacy plugin (a plugin without an api-version in its plugin.yml).
+ *
+ * The server rewrites the classes of legacy plugins while loading them, so they work with the current API.
+ * When that fails, the class is loaded unchanged and the plugin usually breaks as soon as it uses it.
+ * Only a version of the plugin that is made for the current server version helps.
+ * The problem is reported once per plugin, even if several of its classes fail.
+ */
+class LegacyPluginConversionProblem extends PluginProblem
+{
+    /**
+     * @inheritDoc
+     */
+    public function getMessage(): string
+    {
+        return Translator::getInstance()->getTranslation("legacy-plugin-conversion-problem", [
+            "plugin-name" => $this->getPluginName()
+        ]);
+    }
+
+    /**
+     * The plugin is logged with its full name, that is the name and the version with a "v" in front,
+     * followed by the path of the class in the plugin jar.
+     * Example: `Fatal error trying to convert LegacyBrokenClass v1.0:com/repro/BrokenClass.class`
+     *
+     * The plugin name is the first group, so {@see PluginProblem::setMatches()} reads it as `$matches[1]`.
+     *
+     * @inheritDoc
+     */
+    public static function getPatterns(): array
+    {
+        return ['/Fatal error trying to convert (?<plugin>' . PluginProblem::PLUGIN_NAME . ') v[^:\n]+:\S+\.class/'];
+    }
+}