disguise api

and generate maps to allow entity metadata syncher validation

paper-server-generator.settings.gradle.kts

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+// Uncomment to enable the 'paper-server-generator' project
+ include(":paper-server-generator")

paper-server-generator/build.gradle.kts

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+import io.papermc.paperweight.PaperweightSourceGeneratorHelper
+import io.papermc.paperweight.extension.PaperweightSourceGeneratorExt
+
+plugins {
+    java
+}
+
+plugins.apply(PaperweightSourceGeneratorHelper::class)
+
+extensions.configure(PaperweightSourceGeneratorExt::class) {
+    atFile.set(projectDir.toPath().resolve("wideners.at").toFile())
+}
+
+dependencies {
+    implementation("com.squareup:javapoet:1.13.0")
+    implementation(project(":paper-api"))
+    implementation(project(":paper-server"))
+    implementation("io.github.classgraph:classgraph:4.8.47")
+    implementation("org.jetbrains:annotations:24.0.1")
+    testImplementation("org.junit.jupiter:junit-jupiter:5.10.2")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+}
+
+tasks.register<JavaExec>("generate") {
+    dependsOn(tasks.check)
+    mainClass.set("io.papermc.generator.Main")
+    classpath(sourceSets.main.map { it.runtimeClasspath })
+    args(projectDir.toPath().resolve("generated").toString())
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+group = "io.papermc.paper"
+version = "1.0-SNAPSHOT"

paper-server-generator/src/main/java/io/papermc/generator/Generators.java

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+package io.papermc.generator;
+
+import io.papermc.generator.types.EntityMetaWatcherGenerator;
+import io.papermc.generator.types.SourceGenerator;
+
+public interface Generators {
+
+    SourceGenerator[] SERVER = {
+        new EntityMetaWatcherGenerator("EntityMetaWatcher", "io.papermc.paper.entity.meta")
+    };
+}

paper-server-generator/src/main/java/io/papermc/generator/Main.java

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+package io.papermc.generator;
+
+import com.mojang.logging.LogUtils;
+
+import io.papermc.generator.types.SourceGenerator;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.LayeredRegistryAccess;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.resources.RegistryDataLoader;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.RegistryLayer;
+import net.minecraft.server.WorldLoader;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.repository.Pack;
+import net.minecraft.server.packs.repository.PackRepository;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.MultiPackResourceManager;
+import org.apache.commons.io.file.PathUtils;
+import org.slf4j.Logger;
+
+public final class Main {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+    public static final RegistryAccess.Frozen REGISTRY_ACCESS;
+
+    static {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        final PackRepository resourceRepository = ServerPacksSource.createVanillaTrustedRepository();
+        resourceRepository.reload();
+        final MultiPackResourceManager resourceManager = new MultiPackResourceManager(PackType.SERVER_DATA, resourceRepository.getAvailablePacks().stream().map(Pack::open).toList());
+        LayeredRegistryAccess<RegistryLayer> layers = RegistryLayer.createRegistryAccess();
+        layers = WorldLoader.loadAndReplaceLayer(resourceManager, layers, RegistryLayer.WORLDGEN, RegistryDataLoader.WORLDGEN_REGISTRIES);
+        REGISTRY_ACCESS = layers.compositeAccess().freeze();
+    }
+
+    private Main() {
+    }
+
+    public static void main(final String[] args) {
+        LOGGER.info("Running API generators...");
+        generate(Paths.get(args[0]), Generators.SERVER);
+    }
+
+    private static void generate(Path output, SourceGenerator[] generators) {
+        try {
+            if (Files.exists(output)) {
+                PathUtils.deleteDirectory(output);
+            }
+            Files.createDirectories(output);
+
+            for (final SourceGenerator generator : generators) {
+                generator.writeToFile(output);
+            }
+
+            LOGGER.info("Files written to {}", output.toAbsolutePath());
+        } catch (final Exception ex) {
+            throw new RuntimeException(ex);
+        }
+    }
+}

paper-server-generator/src/main/java/io/papermc/generator/types/EntityMetaWatcherGenerator.java

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+package io.papermc.generator.types;
+
+import com.squareup.javapoet.ClassName;
+import com.squareup.javapoet.FieldSpec;
+import com.squareup.javapoet.JavaFile;
+import com.squareup.javapoet.MethodSpec;
+import com.squareup.javapoet.ParameterizedTypeName;
+import com.squareup.javapoet.TypeSpec;
+import com.squareup.javapoet.WildcardTypeName;
+import io.github.classgraph.ClassGraph;
+import io.github.classgraph.ScanResult;
+import io.papermc.generator.utils.Annotations;
+import io.papermc.generator.utils.ReflectionHelper;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.lang.model.element.Modifier;
+import net.minecraft.network.syncher.EntityDataAccessor;
+import net.minecraft.network.syncher.EntityDataSerializer;
+import net.minecraft.network.syncher.EntityDataSerializers;
+import net.minecraft.world.entity.Entity;
+import org.apache.commons.lang3.StringUtils;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+import static io.papermc.generator.utils.Annotations.NOT_NULL;
+
+@DefaultQualifier(NonNull.class)
+public class EntityMetaWatcherGenerator extends SimpleGenerator {
+
+
+    private static final ParameterizedTypeName GENERIC_ENTITY_DATA_SERIALIZER = ParameterizedTypeName.get(ClassName.get(Map.class), ClassName.get(Long.class), ParameterizedTypeName.get(ClassName.get(EntityDataSerializer.class), WildcardTypeName.subtypeOf(Object.class)));
+
+    private static final ParameterizedTypeName ENTITY_CLASS = ParameterizedTypeName.get(
+        ClassName.get(Class.class), WildcardTypeName.subtypeOf(Entity.class));
+    private static final ParameterizedTypeName OUTER_MAP_TYPE = ParameterizedTypeName.get(ClassName.get(Map.class), ENTITY_CLASS, GENERIC_ENTITY_DATA_SERIALIZER);
+
+
+    public EntityMetaWatcherGenerator(String className, String packageName) {
+        super(className, packageName);
+    }
+
+    @Override
+    protected TypeSpec getTypeSpec() {
+
+        Map<EntityDataSerializer<?>, String> dataAccessorStringMap = serializerMap();
+
+        List<Class<?>> classes;
+        try (ScanResult scanResult = new ClassGraph().enableAllInfo().whitelistPackages("net.minecraft").scan()) {
+            classes = scanResult.getSubclasses(net.minecraft.world.entity.Entity.class.getName()).loadClasses();
+        }
+
+
+        classes = classes.stream()
+            .filter(clazz -> !java.lang.reflect.Modifier.isAbstract(clazz.getModifiers()))
+            .toList();
+
+        record Pair(Class<?> clazz, List<? extends EntityDataAccessor<?>> metaResults) {
+        }
+
+        final List<Pair> list = classes.stream()
+            .map(clazz -> new Pair(
+                clazz,
+                    ReflectionHelper.getAllForAllParents(clazz, EntityMetaWatcherGenerator::doFilter)
+                        .stream()
+                        .map(this::createData)
+                        .filter(Objects::nonNull)
+                        .toList()
+                )
+            )
+            .toList();
+
+        Map<Class<?>, List<? extends EntityDataAccessor<?>>> vanillaNames = list.stream()
+            .collect(Collectors.toMap(pair -> pair.clazz, pair -> pair.metaResults));
+
+        TypeSpec.Builder typeBuilder = TypeSpec.classBuilder(this.className)
+            .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
+            .addAnnotations(Annotations.CLASS_HEADER);
+
+        generateIdAccessorMethods(vanillaNames, dataAccessorStringMap, typeBuilder);
+        generateClassToTypeMap(typeBuilder, vanillaNames.keySet());
+        generateIsValidAccessorForEntity(typeBuilder);
+
+        return typeBuilder.build();
+    }
+
+    private void generateIsValidAccessorForEntity(TypeSpec.Builder builder) {
+        var methodBuilder = MethodSpec.methodBuilder("isValidForClass")
+            .addModifiers(Modifier.PUBLIC, Modifier.FINAL, Modifier.STATIC)
+            .returns(boolean.class)
+            .addParameter(ParameterizedTypeName.get(ClassName.get(Class.class), WildcardTypeName.subtypeOf(Entity.class)), "clazz")
+            .addParameter(EntityDataAccessor.class, "accessor")
+            .addStatement("Map<Long, EntityDataSerializer<?>> serializerMap = VALID_ENTITY_META_MAP.get(clazz)")
+            .beginControlFlow("if(serializerMap == null)")
+            .addStatement("return false")
+            .endControlFlow()
+            .addStatement("var serializer = serializerMap.get(accessor.id())")
+            .addStatement("return serializer != null && serializer == accessor.serializer()");
+
+        builder.addMethod(methodBuilder.build());
+    }
+
+    private void generateClassToTypeMap(TypeSpec.Builder typeBuilder, Set<Class<?>> classes){
+
+
+        typeBuilder.addField(
+            FieldSpec.builder(OUTER_MAP_TYPE, "VALID_ENTITY_META_MAP", Modifier.PRIVATE, Modifier.STATIC, Modifier.FINAL)
+                .initializer("initialize()")
+                .build()
+        );
+
+        MethodSpec.Builder builder = MethodSpec.methodBuilder("initialize")
+            .addModifiers(Modifier.PRIVATE, Modifier.STATIC, Modifier.FINAL)
+            .addAnnotations(List.of(NOT_NULL))
+            .returns(OUTER_MAP_TYPE)
+            .addStatement("$T result = new $T<>()", OUTER_MAP_TYPE, ClassName.get(HashMap.class));
+
+        classes.forEach(aClass -> {
+            String name = StringUtils.uncapitalize(aClass.getSimpleName());
+            if(!name.isBlank()) {
+                builder.addStatement("result.put($T.class, $L())", aClass, name);
+            }
+        });
+
+        typeBuilder.addMethod(builder.addStatement("return $T.copyOf(result)", Map.class).build());
+    }
+
+    private static void generateIdAccessorMethods(Map<Class<?>, List<? extends EntityDataAccessor<?>>> vanillaNames, Map<EntityDataSerializer<?>, String> dataAccessorStringMap, TypeSpec.Builder typeBuilder) {
+        for (final Map.Entry<Class<?>, List<? extends EntityDataAccessor<?>>> perClassResults : vanillaNames.entrySet()) {
+
+            if (perClassResults.getKey().getSimpleName().isBlank()) {
+                continue;
+            }
+            var simpleName = perClassResults.getKey().getSimpleName();
+
+            ClassName hashMap = ClassName.get(HashMap.class);
+
+            MethodSpec.Builder builder = MethodSpec.methodBuilder(StringUtils.uncapitalize(simpleName))
+                .addModifiers(Modifier.PRIVATE, Modifier.STATIC, Modifier.FINAL)
+                .addAnnotations(List.of(NOT_NULL))
+                .returns(GENERIC_ENTITY_DATA_SERIALIZER)
+                .addStatement("$T result = new $T<>()", GENERIC_ENTITY_DATA_SERIALIZER, hashMap);
+
+            perClassResults.getValue().forEach(result -> {
+                builder.addStatement("result.put($LL, $T.$L)", result.id(), EntityDataSerializers.class, dataAccessorStringMap.get(result.serializer()));
+            });
+
+            var method = builder.addStatement("return $T.copyOf(result)", Map.class)
+                .build();
+
+            typeBuilder.addMethod(method);
+        }
+    }
+
+    private @Nullable EntityDataAccessor<?> createData(Field field) {
+        try {
+            field.setAccessible(true);
+             return (EntityDataAccessor<?>) field.get(null);
+        } catch (IllegalAccessException e) {
+            return null;
+        }
+    }
+
+    private static boolean doFilter(Field field) {
+        return java.lang.reflect.Modifier.isStatic(field.getModifiers()) && field.getType().isAssignableFrom(EntityDataAccessor.class);
+    }
+
+    @Override
+    protected JavaFile.Builder file(JavaFile.Builder builder) {
+        return builder.skipJavaLangImports(true);
+    }
+
+
+    private Map<EntityDataSerializer<?>, String> serializerMap(){
+        return Arrays.stream(EntityDataSerializers.class.getDeclaredFields())
+            .filter(field -> field.getType() == EntityDataSerializer.class)
+            .map(field -> {
+                try {
+                    return Map.entry((EntityDataSerializer<?>)field.get(0), field.getName());
+                } catch (IllegalAccessException e) {
+                    return null;
+                }
+            })
+            .filter(Objects::nonNull)
+            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+    }
+}

paper-server-generator/src/main/java/io/papermc/generator/types/SimpleGenerator.java

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+package io.papermc.generator.types;
+
+import com.squareup.javapoet.JavaFile;
+import com.squareup.javapoet.TypeSpec;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+public abstract class SimpleGenerator implements SourceGenerator {
+
+    protected final String className;
+    protected final String packageName;
+
+    protected SimpleGenerator(String className, String packageName) {
+        this.className = className;
+        this.packageName = packageName;
+    }
+
+    protected abstract TypeSpec getTypeSpec();
+
+    protected abstract JavaFile.Builder file(JavaFile.Builder builder);
+
+    @Override
+    public void writeToFile(Path parent) throws IOException {
+        Path packagePath = parent.resolve(this.packageName.replace('.', '/'));
+        Files.createDirectories(packagePath);
+
+        JavaFile.Builder builder = JavaFile.builder(this.packageName, this.getTypeSpec())
+            .indent("    ");
+        this.file(builder);
+
+        Files.writeString(packagePath.resolve(this.className + ".java"), this.file(builder).build().toString(), StandardCharsets.UTF_8);
+    }
+
+}

paper-server-generator/src/main/java/io/papermc/generator/types/SourceGenerator.java

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+package io.papermc.generator.types;
+
+import java.io.IOException;
+import java.nio.file.Path;
+
+public interface SourceGenerator {
+
+    void writeToFile(Path parent) throws IOException;
+}