Improve the list codec error messages

Author: ErrorCraft

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

@@ -0,0 +1,57 @@
+package net.errorcraft.codecium.mixin.mojang.serialization.codecs;
+
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import com.llamalad7.mixinextras.sugar.Local;
+import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.DataResult;
+import com.mojang.serialization.codecs.ListCodec;
+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.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+
+import java.util.List;
+import java.util.function.Supplier;
+
+@Mixin(value = ListCodec.class, remap = false)
+public class ListCodecExtender<E> {
+    @Shadow
+    @Final
+    private int minSize;
+
+    @Shadow
+    @Final
+    private int maxSize;
+
+    @ModifyArg(
+        method = "createTooShortError",
+        at = @At(
+            value = "INVOKE",
+            target = "Lcom/mojang/serialization/DataResult;error(Ljava/util/function/Supplier;)Lcom/mojang/serialization/DataResult;"
+        )
+    )
+    private Supplier<String> tooShortUseBetterErrorMessage(Supplier<String> message, @Local(argsOnly = true) final int size) {
+        return () -> "List must have at least " + this.minSize + " " + EnglishUtil.pluralize(this.minSize, "value") + ", but got " + size;
+    }
+
+    @ModifyArg(
+        method = "createTooLongError",
+        at = @At(
+            value = "INVOKE",
+            target = "Lcom/mojang/serialization/DataResult;error(Ljava/util/function/Supplier;)Lcom/mojang/serialization/DataResult;"
+        )
+    )
+    private Supplier<String> tooLongUseBetterErrorMessage(Supplier<String> message, @Local(argsOnly = true) final int size) {
+        return () -> "List must have at most " + this.maxSize + " " + EnglishUtil.pluralize(this.maxSize, "value") + ", but got " + size;
+    }
+
+    @ModifyReturnValue(
+        method = "decode",
+        at = @At("TAIL")
+    )
+    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);
+    }
+}

src/main/java/net/errorcraft/codecium/util/EnglishUtil.java

@@ -0,0 +1,13 @@
+package net.errorcraft.codecium.util;
+
+public class EnglishUtil {
+    private EnglishUtil() {}
+
+    public static String pluralize(int amount, String singular) {
+        return pluralize(amount, singular, singular + "s");
+    }
+
+    public static String pluralize(int amount, String singular, String plural) {
+        return amount == 1 ? singular : plural;
+    }
+}

src/main/resources/codecium.mixins.json

@@ -16,6 +16,7 @@
     "mojang.serialization.codecs.BaseMapCodecExtender",
     "mojang.serialization.codecs.EitherCodecExtender",
     "mojang.serialization.codecs.FieldDecoderExtender",
+    "mojang.serialization.codecs.ListCodecExtender",
     "mojang.serialization.codecs.OptionalFieldCodecExtender",
     "mojang.serialization.codecs.RecordCodecBuilderExtender$RecordMapCodecExtender"
   ],