Add mixin support and example mixin

build.gradle

@@ -1,8 +1,15 @@
+buildscript {
+    repositories {
+        maven { url = 'https://repo.spongepowered.org/repository/maven-public/' }
+    }
+}
+
 plugins {
     id 'eclipse'
     id 'idea'
     id 'maven-publish'
     id 'net.minecraftforge.gradle' version '[6.0,6.2)'
+    id 'org.spongepowered.mixin' version '0.7.+'
 }
 
 version = mod_version
@@ -15,6 +22,9 @@ base {
 // Mojang ships Java 17 to end users in 1.18+, so your mod should target Java 17.
 java.toolchain.languageVersion = JavaLanguageVersion.of(17)
 
+sourceCompatibility = JavaVersion.VERSION_17
+targetCompatibility = JavaVersion.VERSION_17
+
 println "Java: ${System.getProperty 'java.version'}, JVM: ${System.getProperty 'java.vm.version'} (${System.getProperty 'java.vendor'}), Arch: ${System.getProperty 'os.arch'}"
 minecraft {
     // The mappings can be changed at any time and must be in the following format.
@@ -76,6 +86,7 @@ minecraft {
 
             property("mixin.env.remapRefMap", "true")
             property("mixin.env.refMapRemappingFile", "${projectDir}/build/createSrgToMcp/output.srg")
+            args '-mixin.config=contraptionsaresafe.mixins.json'
 
             mods {
                 "${mod_id}" {
@@ -148,6 +159,8 @@ dependencies {
     // The group id is ignored when searching -- in this case, it is "blank"
     // implementation fg.deobf("blank:coolmod-${mc_version}:${coolmod_version}")
 
+    annotationProcessor 'org.spongepowered:mixin:0.8.5:processor'
+
     implementation(fg.deobf("com.simibubi.create:create-${minecraft_version}:${create_version}:slim") { transitive = false })
     implementation(fg.deobf("net.createmod.ponder:Ponder-Forge-${minecraft_version}:${ponder_version}"))
     compileOnly(fg.deobf("dev.engine-room.flywheel:flywheel-forge-api-${minecraft_version}:${flywheel_version}"))
@@ -190,7 +203,9 @@ tasks.named('jar', Jar).configure {
                 'Implementation-Title'    : project.name,
                 'Implementation-Version'  : project.jar.archiveVersion,
                 'Implementation-Vendor'   : mod_authors,
-                'Implementation-Timestamp': new Date().format("yyyy-MM-dd'T'HH:mm:ssZ")
+                'Implementation-Timestamp': new Date().format("yyyy-MM-dd'T'HH:mm:ssZ"),
+                "TSRGFx"                  : "true",
+                "MixinConfigs"            : "contraptionsaresafe.mixins.json"
         ])
     }
 
@@ -203,6 +218,11 @@ tasks.named('jar', Jar).configure {
 //     dependsOn 'reobfJar'
 // }
 
+mixin {
+    add sourceSets.main, "contraptionsaresafe.refmap.json"
+    config "contraptionsaresafe.mixins.json"
+}
+
 // Example configuration to allow publishing using the maven-publish plugin
 publishing {
     publications {

src/main/java/com/bipolarexpedition/java/contraptions_are_safe/mixin/MobTargetingMixin.java

@@ -0,0 +1,33 @@
+package com.bipolarexpedition.java.contraptions_are_safe.mixin;
+
+import com.bipolarexpedition.java.contraptions_are_safe.ContraptionsAreSafe;
+import com.simibubi.create.content.contraptions.AbstractContraptionEntity;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.entity.Mob;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(Mob.class)
+public class MobTargetingMixin {
+
+    @Inject(method = "canAttack(Lnet/minecraft/world/entity/LivingEntity;)Z", at = @At("HEAD"), cancellable = true)
+    private void preventContraptionTargeting(LivingEntity target, CallbackInfoReturnable<Boolean> cir) {
+        if (target != null && isOnContraption(target)) {
+            cir.setReturnValue(false);
+        }
+    }
+
+    private boolean isOnContraption(Entity entity) {
+        Entity vehicle = entity.getVehicle();
+        while (vehicle != null) {
+            if (vehicle instanceof AbstractContraptionEntity) {
+                return true;
+            }
+            vehicle = vehicle.getVehicle();
+        }
+        return false;
+    }
+}

src/main/resources/META-INF/mods.toml

@@ -41,6 +41,8 @@ authors="${mod_authors}" #optional
 # IMPORTANT NOTE: this is NOT an instruction as to which environments (CLIENT or DEDICATED SERVER) your mod loads on. Your mod should load (and maybe do nothing!) whereever it finds itself.
 #displayTest="MATCH_VERSION" # if nothing is specified, MATCH_VERSION is the default when clientSideOnly=false, otherwise IGNORE_ALL_VERSION when clientSideOnly=true (#optional)
 
+mixinConfig = "contraptionsaresafe.mixins.json"
+
 # Access Transformers
 # Optional, if not specified Forge will attempt to find the default META-INF/accesstransformer.cfg and silently continue if not found. May default to an empty list in a future MC.
 # If you specify AT path strings in this list, Forge will attempt to load each of them and throw errors for any that aren't found.

src/main/resources/contraptionsaresafe.mixins.json

@@ -0,0 +1,12 @@
+{
+  "required": true,
+  "minVersion": "0.8",
+  "package": "com.bipolarexpedition.java.contraptions_are_safe.mixin",
+  "compatibilityLevel": "JAVA_17",
+  "refmap": "contraptionsaresafe.refmap.json",
+  "mixins": [
+    "MobTargetingMixin"
+  ],
+  "client": [],
+  "server": []
+}