Improve the record codec error message

Author: ErrorCraft

src/main/java/net/errorcraft/codecium/mixin/mojang/serialization/CodecExtender.java

@@ -1,17 +1,18 @@
 package net.errorcraft.codecium.mixin.mojang.serialization;
 
-import com.mojang.serialization.Codec;
-import com.mojang.serialization.DataResult;
+import com.mojang.serialization.*;
+import net.errorcraft.codecium.serialization.FieldMapCodec;
 import net.errorcraft.codecium.util.codec.NumberUtil;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Overwrite;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Redirect;
 
 import java.util.function.Function;
+import java.util.function.Supplier;
 
 @Mixin(value = Codec.class, remap = false)
-public interface CodecExtender {
+public interface CodecExtender<A> {
     @Redirect(
         method = "intRange",
         at = @At(
@@ -62,4 +63,15 @@ static Codec<String> string(final int minSize, final int maxSize) {
             return DataResult.success(value);
         });
     }
+
+    @Redirect(
+        method = "fieldOf(Ljava/lang/String;)Lcom/mojang/serialization/MapCodec;",
+        at = @At(
+            value = "INVOKE",
+            target = "Lcom/mojang/serialization/MapCodec;of(Lcom/mojang/serialization/MapEncoder;Lcom/mojang/serialization/MapDecoder;Ljava/util/function/Supplier;)Lcom/mojang/serialization/MapCodec;"
+        )
+    )
+    private MapCodec<A> createFieldCodecPassName(MapEncoder<A> encoder, MapDecoder<A> decoder, Supplier<String> nameSupplier, final String name) {
+        return new FieldMapCodec<>(name, encoder, decoder, nameSupplier);
+    }
 }

src/main/java/net/errorcraft/codecium/mixin/mojang/serialization/DataResultExtender.java

@@ -0,0 +1,17 @@
+package net.errorcraft.codecium.mixin.mojang.serialization;
+
+import com.mojang.serialization.DataResult;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+
+@Mixin(value = DataResult.class, remap = false)
+public interface DataResultExtender {
+    /**
+     * @author ErrorCraft
+     * @reason Uses a line feed for a better error message. Also swaps the order of the messages to preserve the order in the codecs.
+     */
+    @Overwrite
+    static String appendMessages(final String first, final String second) {
+        return second + "\n" + first;
+    }
+}

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

@@ -0,0 +1,26 @@
+package net.errorcraft.codecium.mixin.mojang.serialization.codecs;
+
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import com.mojang.serialization.DataResult;
+import com.mojang.serialization.codecs.OptionalFieldCodec;
+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 java.util.Optional;
+
+@Mixin(value = OptionalFieldCodec.class, remap = false)
+public class OptionalFieldCodecExtender<A> {
+    @Shadow
+    @Final
+    private String name;
+
+    @ModifyReturnValue(
+        method = "decode",
+        at = @At("TAIL")
+    )
+    private DataResult<Optional<A>> modifyPotentialErrorMessage(DataResult<Optional<A>> original) {
+        return original.mapError(message -> "'" + this.name + "': " + message);
+    }
+}

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

@@ -0,0 +1,20 @@
+package net.errorcraft.codecium.mixin.mojang.serialization.codecs;
+
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import com.mojang.serialization.DataResult;
+import net.errorcraft.codecium.util.StringUtil;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+
+public class RecordCodecBuilderExtender {
+    @Mixin(targets = "com/mojang/serialization/codecs/RecordCodecBuilder$2", remap = false)
+    public static class RecordMapCodecExtender<O> {
+        @ModifyReturnValue(
+            method = "decode",
+            at = @At("RETURN")
+        )
+        private DataResult<O> useBetterErrorMessage(DataResult<O> original) {
+            return original.mapError(message -> "Map has errors for the following fields:\n" + StringUtil.indent(message));
+        }
+    }
+}

src/main/java/net/errorcraft/codecium/serialization/FieldMapCodec.java

@@ -0,0 +1,41 @@
+package net.errorcraft.codecium.serialization;
+
+import com.mojang.serialization.*;
+
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+public class FieldMapCodec<A> extends MapCodec<A> {
+    private final String name;
+    private final MapEncoder<A> encoder;
+    private final MapDecoder<A> decoder;
+    private final Supplier<String> toStringSupplier;
+
+    public FieldMapCodec(String name, MapEncoder<A> encoder, MapDecoder<A> decoder, Supplier<String> toStringSupplier) {
+        this.name = name;
+        this.encoder = encoder;
+        this.decoder = decoder;
+        this.toStringSupplier = toStringSupplier;
+    }
+
+    @Override
+    public <T> Stream<T> keys(final DynamicOps<T> ops) {
+        return Stream.concat(this.encoder.keys(ops), this.decoder.keys(ops));
+    }
+
+    @Override
+    public <T> DataResult<A> decode(final DynamicOps<T> ops, final MapLike<T> input) {
+        return this.decoder.decode(ops, input)
+            .mapError(message -> "'" + this.name + "': " + message);
+    }
+
+    @Override
+    public <T> RecordBuilder<T> encode(final A input, final DynamicOps<T> ops, final RecordBuilder<T> prefix) {
+        return this.encoder.encode(input, ops, prefix);
+    }
+
+    @Override
+    public String toString() {
+        return this.toStringSupplier.get();
+    }
+}

src/main/resources/codecium.mixins.json

@@ -6,9 +6,12 @@
     "minecraft.nbt.NbtOpsExtender",
     "minecraft.util.dynamic.CodecsExtender",
     "mojang.serialization.CodecExtender",
+    "mojang.serialization.DataResultExtender",
     "mojang.serialization.JavaOpsExtender",
     "mojang.serialization.JsonOpsExtender",
-    "mojang.serialization.codecs.EitherCodecExtender"
+    "mojang.serialization.codecs.EitherCodecExtender",
+    "mojang.serialization.codecs.OptionalFieldCodecExtender",
+    "mojang.serialization.codecs.RecordCodecBuilderExtender$RecordMapCodecExtender"
   ],
   "injectors": {
     "defaultRequire": 1