Check for "fields" field

2 files changed, 11 insertions, 1 deletions

diff --git a/document/src/main/java/com/yahoo/document/json/JsonReader.java b/document/src/main/java/com/yahoo/document/json/JsonReader.java
index adf876262fa..b6cf8c6e18b 100644
--- a/document/src/main/java/com/yahoo/document/json/JsonReader.java
+++ b/document/src/main/java/com/yahoo/document/json/JsonReader.java
@@ -136,7 +136,8 @@ public class JsonReader {
             if (null != parser.nextToken())
                 throw new IllegalArgumentException("expected end of input, got " + parser.currentToken());
 
-            assert null != operation: "VespaDocumentReader should throw on missing fields";
+            if (null == operation)
+                throw new IllegalArgumentException("document is missing the required \"fields\" field");
 
             if (null != create) {
                 switch (operationType) {
diff --git a/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java b/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java
index 12ccba62005..aa043a25d78 100644
--- a/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java
+++ b/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java
@@ -222,6 +222,15 @@ public class JsonReaderTestCase {
     }
 
     @Test
+    public void readDocumentWithMissingFieldsField() {
+        assertEquals("document is missing the required \"fields\" field",
+                     assertThrows(IllegalArgumentException.class,
+                                  () -> createReader("{ }").readSingleDocumentStreaming(DocumentOperationType.PUT,
+                                                                                        "id:unittest:testnull::whee"))
+                             .getMessage());
+    }
+
+    @Test
     public void readSingleDocumentsPutStreaming() throws IOException {
         String json = """
                       {