Better error messages for unserializable annotations (#1885)

1 files changed, 12 insertions, 1 deletions

diff --git a/src/test/scala/firrtlTests/annotationTests/JsonProtocolSpec.scala b/src/test/scala/firrtlTests/annotationTests/JsonProtocolSpec.scala
index 54a94edb..44ad7d1f 100644
--- a/src/test/scala/firrtlTests/annotationTests/JsonProtocolSpec.scala
+++ b/src/test/scala/firrtlTests/annotationTests/JsonProtocolSpec.scala
@@ -3,12 +3,14 @@
 package firrtlTests.annotationTests
 
 import firrtl._
-import firrtl.annotations.{JsonProtocol, NoTargetAnnotation}
+import firrtl.annotations.{JsonProtocol, NoTargetAnnotation, UnserializableAnnotationException}
 import firrtl.ir._
 import firrtl.options.Dependency
+import scala.util.Failure
 import _root_.logger.{LogLevel, LogLevelAnnotation, Logger}
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should._
+import org.scalatest.Inside._
 
 case class AnAnnotation(
   info:       Info,
@@ -66,4 +68,13 @@ class JsonProtocolSpec extends AnyFlatSpec with Matchers {
       compiler.execute(CircuitState(circuit, Nil))
     }
   }
+  "Trying to serialize annotations that cannot be serialized" should "tell you why" in {
+    case class MyAnno(x: Int) extends NoTargetAnnotation
+    inside(JsonProtocol.serializeTry(MyAnno(3) :: Nil)) {
+      case Failure(e: UnserializableAnnotationException) =>
+        e.getMessage should include("MyAnno")
+        // From json4s Exception
+        e.getMessage should include("Classes defined in method bodies are not supported")
+    }
+  }
 }