surround my dynamics

src/main/java/com/falsepattern/endlessids/mixin/mixins/common/antiidconflict/BiomeGenBasePlaceholderMixin.java

@@ -23,8 +23,10 @@ public abstract class BiomeGenBasePlaceholderMixin {
                        remap = false),
               require = 1)
     private int removePlaceholders(int id, boolean register) {
-        if (biomeList[id] instanceof PlaceholderBiome) {
-            biomeList[id] = null;
+        if (register) {
+            if (biomeList[id] instanceof PlaceholderBiome) {
+                biomeList[id] = null;
+            }
         }
         return AsmHooks.getBiomeID(id, register);
     }

src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/biome/BiomeGenBaseMixin.java

@@ -34,8 +34,8 @@ public abstract class BiomeGenBaseMixin {
     @Inject(method = "<init>(IZ)V",
             at = @At(value = "RETURN"),
             require = 1)
-    private void generatePlaceholders(int p_i1971_1_, boolean register, CallbackInfo ci) {
-        if (((Object) this) instanceof PlaceholderBiome) {
+    private void generatePlaceholders(int id, boolean register, CallbackInfo ci) {
+        if (((Object) this) instanceof PlaceholderBiome || !register) {
             return;
         }
         if (biomeID >= 128 && biomeList[biomeID - 128] == null) {

src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/biome/BiomeGenBasePlaceholderMixin.java

@@ -7,6 +7,7 @@ import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Mutable;
 import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
 import org.spongepowered.asm.mixin.injection.Redirect;
 
 import net.minecraft.world.biome.BiomeGenBase;
@@ -22,15 +23,30 @@ public abstract class BiomeGenBasePlaceholderMixin {
     @Final
     public int biomeID;
 
+    private static ThreadLocal<Boolean> wantsRegister;
+
     @Redirect(method = "<init>(IZ)V",
               at = @At(value = "FIELD",
                        opcode = Opcodes.PUTFIELD,
                        target = "Lnet/minecraft/world/biome/BiomeGenBase;biomeID:I"),
               require = 1)
     private void removePlaceholders(BiomeGenBase instance, int id) {
-        if (biomeList[id] instanceof PlaceholderBiome) {
-            biomeList[id] = null;
+        if (wantsRegister.get()) {
+            if (biomeList[id] instanceof PlaceholderBiome) {
+                biomeList[id] = null;
+            }
         }
         biomeID = id;
     }
+
+    @ModifyVariable(method = "<init>(IZ)V",
+                    at = @At(value = "HEAD"),
+                    index = 2,
+                    require = 1,
+                    argsOnly = true)
+    private static boolean modifyArg(boolean register) {
+        if (wantsRegister == null) wantsRegister = new ThreadLocal<>();
+        wantsRegister.set(register);
+        return register;
+    }
 }