From 2b875517f7595eee4a95fc5a2cc7c1198247590a Mon Sep 17 00:00:00 2001
From: github-vincent-baret <vincent.baret@teads.tv>
Date: Wed, 19 Jul 2023 15:07:21 +0200
Subject: [PATCH] Update JsonFormatException with field name and exception

---
 .../scala/scalapb/json4s/JsonFormat.scala     | 25 +++++++++++++------
 .../scala/scalapb/json4s/JsonFormatSpec.scala | 11 ++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/src/main/scala/scalapb/json4s/JsonFormat.scala b/src/main/scala/scalapb/json4s/JsonFormat.scala
index 0c2b44c..af22bd2 100644
--- a/src/main/scala/scalapb/json4s/JsonFormat.scala
+++ b/src/main/scala/scalapb/json4s/JsonFormat.scala
@@ -423,6 +423,7 @@ class Printer private (config: Printer.PrinterConfig) {
     )
 
   private def unsignedInt(n: Int): Long = n & 0x00000000ffffffffL
+
   private def unsignedLong(n: Long): BigInt =
     if (n < 0) BigInt(n & 0x7fffffffffffffffL).setBit(63) else BigInt(n)
 
@@ -723,11 +724,19 @@ class Parser private (config: Parser.ParserConfig) {
         res.fold[PValue](PEmpty)(PEnum.apply)
       }
       case ScalaType.Message(md) =>
-        fromJsonToPMessage(
-          containerCompanion.messageCompanionForFieldNumber(fd.number),
-          value,
-          false
-        )
+        try {
+          fromJsonToPMessage(
+            containerCompanion.messageCompanionForFieldNumber(fd.number),
+            value,
+            false
+          )
+        } catch {
+          case ex: JsonFormatException =>
+            throw new JsonFormatException(
+              s"Failed parsing field ${fd.name}: ${ex.getMessage}",
+              ex
+            )
+        }
       case st =>
         JsonFormat.parsePrimitive(
           fd.protoType,
@@ -740,6 +749,7 @@ class Parser private (config: Parser.ParserConfig) {
 }
 
 object JsonFormat {
+
   import com.google.protobuf.wrappers
 
   // type GenericCompanion = GeneratedMessageCompanion[T] forSome { type T <: GeneratedMessage}
@@ -875,8 +885,9 @@ object JsonFormat {
 
   def fromJsonEither[A <: GeneratedMessage: GeneratedMessageCompanion](
       value: JValue
-  ): Either[MappingException, A] = try { Right(parser.fromJson(value)) }
-  catch {
+  ): Either[MappingException, A] = try {
+    Right(parser.fromJson(value))
+  } catch {
     case e: JsonFormatException => Left(new MappingException("fail", e))
   }
 
diff --git a/src/test/scala/scalapb/json4s/JsonFormatSpec.scala b/src/test/scala/scalapb/json4s/JsonFormatSpec.scala
index e030fb1..5d6cdea 100644
--- a/src/test/scala/scalapb/json4s/JsonFormatSpec.scala
+++ b/src/test/scala/scalapb/json4s/JsonFormatSpec.scala
@@ -456,6 +456,17 @@ class JsonFormatSpec
     )
   }
 
+  "TestProto" should "fail to parse when a message field is not a json object" in {
+    val jsonFormatException = intercept[JsonFormatException] {
+      new Parser().fromJsonString[MyTest](
+        """{"optMessage": 39}"""
+      )
+    }
+    jsonFormatException.getMessage must be (
+      "Failed parsing field opt_message: Expected an object, found JInt(39)"
+    )
+  }
+
   "TestProto" should "parse original field names" in {
     new Parser().fromJsonString[MyTest]("""{"opt_enum":1}""") must be(
       MyTest(optEnum = Some(MyEnum.V1))