Improve help output, display plugin information

plugins/idea-not-null/src/main/java/org/vineflower/ideanotnull/IdeaNotNullPlugin.java

@@ -14,6 +14,11 @@ public String id() {
     return "IdeaNotNull";
   }
 
+  @Override
+  public String description() {
+    return "Decompiles code inserted by Intellij IDEA's @NotNull annotation.";
+  }
+
   @Override
   public void registerJavaPasses(JavaPassRegistrar registrar) {
     registrar.register(JavaPassLocation.MAIN_LOOP, new NamedPass("IdeaNotNull", new IdeaNotNullPass()));

plugins/kotlin/src/main/java/org/vineflower/kotlin/KotlinPlugin.java

@@ -25,6 +25,11 @@ public String id() {
     return "Kotlin";
   }
 
+  @Override
+  public String description() {
+    return "Detects and decompiles Kotlin class files.";
+  }
+
   @Override
   public @Nullable PluginOptions getPluginOptions() {
     return () -> Pair.of(KotlinOptions.class, KotlinOptions::addDefaults);

plugins/scala/src/main/java/org/vineflower/scala/ScalaPlugin.java

@@ -2,9 +2,14 @@
 
 import org.jetbrains.java.decompiler.api.plugin.Plugin;
 
-public class ScalaPlugin implements Plugin{
+public class ScalaPlugin implements Plugin {
 
   public String id(){
     return "Scala";
   }
+
+  @Override
+  public String description() {
+    return "Detects and decompiles Scala class files.";
+  }
 }

plugins/variable-renaming/src/main/java/org/vineflower/variablerenaming/VariableRenamingPlugin.java

@@ -13,6 +13,11 @@ public String id() {
     return "VariableRenaming";
   }
 
+  @Override
+  public String description() {
+    return "Allows automatic renaming of variables with a common naming scheme.";
+  }
+
   @Override
   public @Nullable PluginOptions getPluginOptions() {
     return () -> Pair.of(VariableRenamingOptions.class, VariableRenamingOptions::addDefaults);

src/org/jetbrains/java/decompiler/api/plugin/Plugin.java

@@ -15,6 +15,12 @@ public interface Plugin {
    */
   String id();
 
+  /**
+   * Short (1-2 sentence) long description of the plugin and its function. This will be presented to users when requested via terminal.
+   * @return a short description of the plugin
+   */
+  String description();
+
   /**
    * Allows addition to the list of passes that will be run during Java decompilation.
    *

src/org/jetbrains/java/decompiler/main/decompiler/ConsoleDecompiler.java

@@ -69,10 +69,16 @@ else if (args.length > x+1) {
       return;
     }
 
+    if (Arrays.stream(args).anyMatch(arg -> arg.equals("--list-plugins"))) {
+      ConsoleHelp.printPlugins();
+      return;
+    }
+
     if (args.length < 1) {
       System.out.println(
+        "=== Vineflower Decompiler " + version() + " ===\n\n" +
         "Usage: java -jar vineflower.jar --<option>=<value>... <source>... <destination>\n" +
-        "Example: java -jar vineflower.jar --decompile-generics ./MyJar.jar ./out_files\n" +
+        "Example: java -jar vineflower.jar --decompile-generics ./MyJar.jar ./out_files\n\n" +
         "Use -h or --help for more information.");
       return;
     }
@@ -431,4 +437,9 @@ public Function<File, IResultSaver> getSaver() {
       return saver;
     }
   }
+
+  public static String version() {
+    String ver = ConsoleDecompiler.class.getPackage().getImplementationVersion();
+    return ver == null ? "<UNK>" : ver;
+  }
 }

src/org/jetbrains/java/decompiler/main/decompiler/ConsoleHelp.java

@@ -12,32 +12,37 @@
 
 public class ConsoleHelp {
   private static final String[] DEFAULT_HELP = {
+    "=== Vineflower Decompiler " + ConsoleDecompiler.version() + " ===",
+    "",
+    "--- Command-line options ---",
+    "-h, --help: Print this help screen",
+    "-s, --silent: Only print to the console if an error is raised",
+    "--list-plugins: Displays loaded plugin information",
+    "",
+    "--- Decompiler usage ---",
     "Usage: java -jar vineflower.jar --<option>=<value>... <source>... <destination>",
     "At least one source file or directory must be specified.",
-    "Options:",
-    "-h, --help: Show this help",
-    "-s, --silent: Only print to console if an error is raised",
     "",
-    "Saving options",
+    "--- Saving options ---",
     "A maximum of one of the options can be specified:",
     "--file          - Write the decompiled source to a file",
     "--folder        - Write the decompiled source to a folder",
     "--legacy-saving - Use the legacy console-specific method of saving",
     "If unspecified, the decompiled source will be automatically detected based on destination name.",
     "",
-    "General options",
+    "--- General options ---",
     "These options can be specified multiple times.",
     "-e=<path>, --add-external=<path> - Add the specified path to the list of external libraries",
     "-only=<class>, --only=<class>    - Only decompile the specified class",
     "",
-    "Additional options",
+    "--- Additional options ---",
     "These options take the last specified value.",
     "They are mostly specified with a name followed by an equals sign, followed by the value.",
     "Boolean options can also be specified without a value, in which case they are treated as `true`.",
     "They can also be specified with a `no-` prefix, in which case they are treated as `false`.",
     "For example, `--decompile-generics` is equivalent to `--decompile-generics=true`.",
     "",
-    "Options from the core decompiler:"
+    "====== Options from the core decompiler ======"
     // Options are added at runtime
   };
 
@@ -73,7 +78,7 @@ static void printHelp() {
 
         if (!pluginFields.isEmpty()) {
           System.out.println();
-          System.out.println("Options for plugin '" + plugin.id() + "':");
+          System.out.println("====== Options for plugin '" + plugin.id() + "' ======");
           writeOptions(pluginFields, pluginDefaults);
         }
       }
@@ -121,30 +126,49 @@ private static void writeOptions(List<Field> fields, Map<String, Object> default
         .append(" ".repeat(Math.max(8 - type.value().length(), 0)))
         .append(name.value())
         .append(" ".repeat(Math.max(50 - name.value().length(), 0)))
-        .append(": ")
-        .append(description.value());
+        .append(":");
 
+      StringBuilder sb2 = new StringBuilder();
       if (defaults.containsKey(paramName)) {
-        sb.append(" (default: ");
+        sb2.append(" (default: ");
         Object value = defaults.get(paramName);
         switch (type.value()) {
           case IFernflowerPreferences.Type.BOOLEAN:
-            sb.append(value.equals("1"));
+            sb2.append(value.equals("1"));
             break;
           case IFernflowerPreferences.Type.STRING:
-            sb.append('"').append(value).append('"');
+            sb2.append('"').append(value).append('"');
             break;
           default:
-            sb.append(value);
+            sb2.append(value);
             break;
         }
-        sb.append(")");
+        sb2.append(")");
+        sb2.append(" ".repeat(Math.max(18 - sb2.length(), 1)));
+        sb.append(sb2);
       }
 
+      sb.append(description.value());
+
       System.out.println(sb);
     }
   }
 
+  static void printPlugins() {
+    System.out.println("=== Vineflower Decompiler " + ConsoleDecompiler.version() + " ===");
+    System.out.println();
+
+    PluginContext ctx = new PluginContext();
+    ctx.findPlugins();
+
+    System.out.println("Loaded " + ctx.getPlugins().size() + " plugins:");
+    for (Plugin plugin : ctx.getPlugins()) {
+      System.out.println(plugin.id() + " (loaded from " + ctx.getSource(plugin).getClass().getSimpleName() + ")");
+      System.out.println(" - " + plugin.description());
+      System.out.println();
+    }
+  }
+
    static {
      Init.init();
    }

src/org/jetbrains/java/decompiler/main/plugins/PluginContext.java

@@ -19,6 +19,7 @@
 
 public class PluginContext {
   private final List<Plugin> plugins = new ArrayList<>();
+  private final Map<Plugin, PluginSource> bySource = new HashMap<>();
   private boolean initialized = false;
   private Map<JavaPassLocation, List<NamedPass>> passes = new HashMap<>();
   private final Map<Plugin, LanguageSpec> languageSpecs = new HashMap<>();
@@ -28,15 +29,16 @@ public static PluginContext getCurrentContext() {
     return DecompilerContext.getCurrentContext().structContext.getPluginContext();
   }
 
-  private void registerPlugin(Plugin plugin) {
+  private void registerPlugin(Plugin plugin, PluginSource source) {
     plugins.add(plugin);
+    bySource.put(plugin, source);
   }
 
   public int findPlugins() {
     int pluginCount = 0;
     for (PluginSource source : PluginSources.PLUGIN_SOURCES) {
       for (Plugin plugin : source.findPlugins()) {
-        registerPlugin(plugin);
+        registerPlugin(plugin, source);
         pluginCount++;
       }
     }
@@ -113,6 +115,10 @@ public IVariableNamingFactory getVariableRenamer() {
     return null;
   }
 
+  public PluginSource getSource(Plugin plugin) {
+    return bySource.get(plugin);
+  }
+
   public List<Plugin> getPlugins() {
     return Collections.unmodifiableList(plugins);
   }