Only add the input for size-related errors in lists, fixes #1

Author: ErrorCraft

src/main/java/net/errorcraft/codecium/access/mojang/serialization/codecs/ListCodecAccess.java

@@ -0,0 +1,7 @@
+package net.errorcraft.codecium.access.mojang.serialization.codecs;
+
+public interface ListCodecAccess {
+    default Object codecium$getAndRemoveTemporaryInput() {
+        throw new AssertionError();
+    }
+}

src/main/java/net/errorcraft/codecium/mixin/mojang/serialization/codecs/ListCodecExtender.java

@@ -1,22 +1,27 @@
 package net.errorcraft.codecium.mixin.mojang.serialization.codecs;
 
-import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
 import com.llamalad7.mixinextras.sugar.Local;
 import com.mojang.datafixers.util.Pair;
 import com.mojang.serialization.DataResult;
+import com.mojang.serialization.DynamicOps;
 import com.mojang.serialization.codecs.ListCodec;
+import net.errorcraft.codecium.access.mojang.serialization.codecs.ListCodecAccess;
 import net.errorcraft.codecium.util.EnglishUtil;
 import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
 import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.ModifyArg;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 import java.util.List;
 import java.util.function.Supplier;
 
 @Mixin(value = ListCodec.class, remap = false)
-public class ListCodecExtender<E> {
+public class ListCodecExtender<E> implements ListCodecAccess {
     @Shadow
     @Final
     private int minSize;
@@ -25,6 +30,9 @@ public class ListCodecExtender<E> {
     @Final
     private int maxSize;
 
+    @Unique
+    private Object temporaryInput;
+
     @ModifyArg(
         method = "createTooShortError",
         at = @At(
@@ -47,11 +55,47 @@ private Supplier<String> tooLongUseBetterErrorMessage(Supplier<String> message,
         return () -> "List must have at most " + this.maxSize + " " + EnglishUtil.pluralize(this.maxSize, "value") + ", but got " + size;
     }
 
-    @ModifyReturnValue(
+    @Inject(
         method = "decode",
-        at = @At("TAIL")
+        at = @At("HEAD")
     )
-    private <T> DataResult<Pair<List<E>, T>> listErrorAddListToErrorMessage(DataResult<Pair<List<E>, T>> original, @Local(argsOnly = true) final T input) {
-        return original.mapError(message -> message + ": " + input);
+    private <T> void storeTemporaryInput(DynamicOps<T> ops, T input, CallbackInfoReturnable<DataResult<Pair<List<E>, T>>> info) {
+        this.temporaryInput = input;
+    }
+
+    @Override
+    public Object codecium$getAndRemoveTemporaryInput() {
+        Object input = this.temporaryInput;
+        this.temporaryInput = null;
+        return input;
+    }
+
+    @Mixin(targets = "com/mojang/serialization/codecs/ListCodec$DecoderState", remap = false)
+    public static class DecoderStateExtender<T> {
+        @Shadow
+        @Final
+        ListCodec<T> this$0;
+
+        @ModifyExpressionValue(
+            method = "build",
+            at = @At(
+                value = "INVOKE",
+                target = "Lcom/mojang/serialization/codecs/ListCodec;createTooShortError(I)Lcom/mojang/serialization/DataResult;"
+            )
+        )
+        private <R> DataResult<R> tooShortAddListToErrorMessage(DataResult<R> original) {
+            return original.mapError(message -> message + ": " + ((ListCodecAccess)(Object) this.this$0).codecium$getAndRemoveTemporaryInput());
+        }
+
+        @ModifyExpressionValue(
+            method = "build",
+            at = @At(
+                value = "INVOKE",
+                target = "Lcom/mojang/serialization/codecs/ListCodec;createTooLongError(I)Lcom/mojang/serialization/DataResult;"
+            )
+        )
+        private <R> DataResult<R> tooLongAddListToErrorMessage(DataResult<R> original) {
+            return original.mapError(message -> message + ": " + ((ListCodecAccess)(Object) this.this$0).codecium$getAndRemoveTemporaryInput());
+        }
     }
 }

src/main/resources/codecium.mixins.json

@@ -22,6 +22,7 @@
     "mojang.serialization.codecs.FieldDecoderExtender",
     "mojang.serialization.codecs.KeyDispatchCodecExtender",
     "mojang.serialization.codecs.ListCodecExtender",
+    "mojang.serialization.codecs.ListCodecExtender$DecoderStateExtender",
     "mojang.serialization.codecs.OptionalFieldCodecExtender",
     "mojang.serialization.codecs.RecordCodecBuilderExtender$RecordMapCodecExtender",
     "mojang.serialization.codecs.XorCodecExtender"