Use FML's scan data to gather annotations

We can just scrape them from the @autoservice annotation, which saves us
having to duplicate any work. Hopefully fixes #501, but I haven't tested
in a non-dev environment yet.

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -8,6 +8,7 @@
 import dan200.computercraft.api.turtle.event.TurtleAction;
 import dan200.computercraft.core.apis.http.options.Action;
 import dan200.computercraft.core.apis.http.options.AddressRule;
+import dan200.computercraft.core.asm.GenericSource;
 import dan200.computercraft.shared.Config;
 import dan200.computercraft.shared.Registry;
 import dan200.computercraft.shared.computer.core.ClientComputerRegistry;
@@ -16,6 +17,7 @@
 import dan200.computercraft.shared.pocket.peripherals.PocketModem;
 import dan200.computercraft.shared.pocket.peripherals.PocketSpeaker;
 import dan200.computercraft.shared.turtle.upgrades.*;
+import dan200.computercraft.shared.util.ServiceUtil;
 import net.minecraftforge.fml.common.Mod;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -133,6 +135,6 @@ public ComputerCraft()
     {
         Config.setup();
         Registry.setup();
+        GenericSource.setup( () -> ServiceUtil.loadServicesForge( GenericSource.class ) );
     }
-
 }

src/main/java/dan200/computercraft/core/asm/GenericSource.java

@@ -9,18 +9,20 @@
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.lua.LuaFunction;
 import dan200.computercraft.shared.peripheral.generic.GenericPeripheralProvider;
+import dan200.computercraft.shared.util.ServiceUtil;
 import net.minecraft.util.ResourceLocation;
 
 import javax.annotation.Nonnull;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Type;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
-import java.util.ServiceLoader;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
-import java.util.stream.StreamSupport;
+import java.util.stream.Stream;
 
 /**
  * A generic source of {@link LuaMethod} functions. This allows for injecting methods onto objects you do not own.
@@ -42,6 +44,18 @@ public interface GenericSource
     @Nonnull
     ResourceLocation id();
 
+    /**
+     * Register a stream of generic sources.
+     *
+     * @param sources The source of generic methods.
+     * @see ServiceUtil For ways to load this. Sadly {@link java.util.ServiceLoader} is broken under Forge, but we don't
+     * want to add a hard-dep on Forge within core either.
+     */
+    static void setup( Supplier<Stream<GenericSource>> sources )
+    {
+        GenericMethod.sources = sources;
+    }
+
     /**
      * A generic method is a method belonging to a {@link GenericSource} with a known target.
      */
@@ -51,6 +65,7 @@ class GenericMethod
         final LuaFunction annotation;
         final Class<?> target;
 
+        static Supplier<Stream<GenericSource>> sources;
         private static List<GenericMethod> cache;
 
         GenericMethod( Method method, LuaFunction annotation, Class<?> target )
@@ -68,10 +83,16 @@ class GenericMethod
         static List<GenericMethod> all()
         {
             if( cache != null ) return cache;
-            return cache = StreamSupport
-                .stream( ServiceLoader.load( GenericSource.class, GenericSource.class.getClassLoader() ).spliterator(), false )
+            if( sources == null )
+            {
+                ComputerCraft.log.warn( "Getting GenericMethods without a provider" );
+                return cache = Collections.emptyList();
+            }
+
+            return cache = sources.get()
                 .flatMap( x -> Arrays.stream( x.getClass().getDeclaredMethods() ) )
-                .map( method -> {
+                .map( method ->
+                {
                     LuaFunction annotation = method.getAnnotation( LuaFunction.class );
                     if( annotation == null ) return null;
 

src/main/java/dan200/computercraft/shared/util/ServiceUtil.java

@@ -0,0 +1,63 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.util;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.ComputerCraftAPI;
+import net.minecraftforge.fml.ModList;
+import org.objectweb.asm.Type;
+
+import java.util.List;
+import java.util.ServiceLoader;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public final class ServiceUtil
+{
+    private static final Type AUTO_SERVICE = Type.getType( "Lcom/google/auto/service/AutoService;" );
+
+    private ServiceUtil()
+    {
+    }
+
+    public static <T> Stream<T> loadServices( Class<T> target )
+    {
+        return StreamSupport.stream( ServiceLoader.load( target, ServiceUtil.class.getClassLoader() ).spliterator(), false );
+    }
+
+    public static <T> Stream<T> loadServicesForge( Class<T> target )
+    {
+        Type type = Type.getType( target );
+        ClassLoader loader = ComputerCraftAPI.class.getClassLoader();
+        return ModList.get().getAllScanData().stream()
+            .flatMap( x -> x.getAnnotations().stream() )
+            .filter( x -> x.getAnnotationType().equals( AUTO_SERVICE ) )
+            .filter( x -> {
+                Object value = x.getAnnotationData().get( "value" );
+                return value instanceof List<?> && ((List<?>) value).contains( type );
+            } )
+            .flatMap( x -> {
+                try
+                {
+                    Class<?> klass = loader.loadClass( x.getClassType().getClassName() );
+                    if( !target.isAssignableFrom( klass ) )
+                    {
+                        ComputerCraft.log.error( "{} is not a subtype of {}", x.getClassType().getClassName(), target.getName() );
+                        return Stream.empty();
+                    }
+
+                    Class<? extends T> casted = klass.asSubclass( target );
+                    return Stream.of( casted.newInstance() );
+                }
+                catch( ReflectiveOperationException e )
+                {
+                    ComputerCraft.log.error( "Cannot load {}", x.getClassType(), e );
+                    return Stream.empty();
+                }
+            } );
+    }
+}