When an exception was thrown from a dataloader, it would be wrapped i…

graphql-dgs/src/main/kotlin/com/netflix/graphql/dgs/exceptions/DefaultDataFetcherExceptionHandler.kt

@@ -24,6 +24,7 @@ import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import org.springframework.util.ClassUtils
 import java.util.concurrent.CompletableFuture
+import java.util.concurrent.CompletionException
 
 /**
  * Default DataFetcherExceptionHandler used by the framework, can be replaced with a custom implementation.
@@ -41,7 +42,7 @@ class DefaultDataFetcherExceptionHandler : DataFetcherExceptionHandler {
     }
 
     private fun doHandleException(handlerParameters: DataFetcherExceptionHandlerParameters): DataFetcherExceptionHandlerResult {
-        val exception = handlerParameters.exception
+        val exception = unwrapCompletionException(handlerParameters.exception)
         logger.error(
             "Exception while executing data fetcher for ${handlerParameters.path}: ${exception.message}",
             exception
@@ -62,6 +63,10 @@ class DefaultDataFetcherExceptionHandler : DataFetcherExceptionHandler {
             .build()
     }
 
+    private fun unwrapCompletionException(e: Throwable): Throwable {
+        return if (e is CompletionException && e.cause != null) e.cause!! else e
+    }
+
     companion object {
 
         private val logger: Logger = LoggerFactory.getLogger(DefaultDataFetcherExceptionHandler::class.java)

graphql-dgs/src/test/kotlin/com/netflix/graphql/dgs/exceptions/DefaultDataFetcherExceptionHandlerTest.kt

@@ -26,6 +26,7 @@ import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 import org.springframework.security.access.AccessDeniedException
+import java.util.concurrent.CompletionException
 
 internal class DefaultDataFetcherExceptionHandlerTest {
 
@@ -126,4 +127,22 @@ internal class DefaultDataFetcherExceptionHandlerTest {
         // We return null here because we don't want graphql-java to write classification field
         assertThat(result.errors[0].errorType).isNull()
     }
+
+    @Test
+    fun `CompletionException returns wrapped error code`() {
+        val completionException = CompletionException(
+            "com.netflix.graphql.dgs.exceptions.DgsEntityNotFoundException: Requested entity not found",
+            DgsEntityNotFoundException()
+        )
+        every { dataFetcherExceptionHandlerParameters.exception }.returns(completionException)
+
+        val result = DefaultDataFetcherExceptionHandler().handleException(dataFetcherExceptionHandlerParameters).get()
+        assertThat(result.errors.size).isEqualTo(1)
+
+        val extensions = result.errors[0].extensions
+        assertThat(extensions["errorType"]).isEqualTo("NOT_FOUND")
+
+        // We return null here because we don't want graphql-java to write classification field
+        assertThat(result.errors[0].errorType).isNull()
+    }
 }