Add named objects

3 files changed, 25 insertions, 1 deletions

diff --git a/gson/src/test/java/moe/nea/jcp/gson/test/TestBasic.java b/gson/src/test/java/moe/nea/jcp/gson/test/TestBasic.java
index 861656e..70c4345 100644
--- a/gson/src/test/java/moe/nea/jcp/gson/test/TestBasic.java
+++ b/gson/src/test/java/moe/nea/jcp/gson/test/TestBasic.java
@@ -16,6 +16,7 @@ import moe.nea.pcj.json.DuplicateJsonKey;
 import moe.nea.pcj.json.JsonLikeError;
 import moe.nea.pcj.json.JsonLikeOperations;
 import moe.nea.pcj.json.MissingKey;
+import moe.nea.pcj.json.NamedObject;
 import moe.nea.pcj.json.RecordJoiners;
 import moe.nea.pcj.json.UnexpectedJsonElement;
 import org.junit.jupiter.api.Assertions;
@@ -97,6 +98,12 @@ public class TestBasic {
 
 
 	@Test
+	void testNamedFunction() {
+		assertFail(decode(codecs.STRING.named("Test"), mkPrim(0)),
+		           new NamedObject("Test", new UnexpectedJsonElement("string", mkPrim(0))));
+	}
+
+	@Test
 	void testObject() {
 		var codec = RecordJoiners.join(
 				codecs.STRING.fieldOf("foo").withGetter(TestObject::foo),
diff --git a/src/main/java/moe/nea/pcj/json/JsonCodec.java b/src/main/java/moe/nea/pcj/json/JsonCodec.java
index 6195bee..c5c750b 100644
--- a/src/main/java/moe/nea/pcj/json/JsonCodec.java
+++ b/src/main/java/moe/nea/pcj/json/JsonCodec.java
@@ -2,7 +2,6 @@ package moe.nea.pcj.json;
 
 import moe.nea.pcj.Codec;
 import moe.nea.pcj.Result;
-import moe.nea.pcj.Unit;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -47,6 +46,20 @@ public interface JsonCodec<T, Format> extends Codec<
 		};
 	}
 
+	default JsonCodec<T, Format> named(String name) {
+		return new JsonCodec<>() {
+			@Override
+			public Result<? extends T, JsonLikeError> decode(Format format, JsonLikeOperations<Format> ops) {
+				return JsonCodec.this.decode(format, ops).mapError(it -> new NamedObject(name, it));
+			}
+
+			@Override
+			public Result<? extends Format, JsonLikeError> encode(T data, JsonLikeOperations<Format> ops) {
+				return JsonCodec.this.encode(data, ops).mapError(it -> new NamedObject(name, it));
+			}
+		};
+	}
+
 	default MapCodec<T, Format> fieldOf(String key) {
 		return new MapCodec<>() {
 			@Override
diff --git a/src/main/java/moe/nea/pcj/json/NamedObject.java b/src/main/java/moe/nea/pcj/json/NamedObject.java
new file mode 100644
index 0000000..aedc87b
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/json/NamedObject.java
@@ -0,0 +1,4 @@
+package moe.nea.pcj.json;
+
+public record NamedObject(String name, JsonLikeError error) implements JsonLikeError {
+}