Google Gemini - handling a case where Content is empty ({}) with custom Reads and Writes; add test for deserialization of empty content

Author: peterbanda

google-gemini-client/src/main/scala/io/cequence/openaiscala/gemini/JsonFormats.scala

@@ -79,7 +79,20 @@ trait JsonFormats {
 
   implicit val partFormat: Format[Part] = Format(partReads, partWrites)
 
-  implicit val contentFormat: Format[Content] = Json.format[Content]
+  implicit val contentWrites: Writes[Content] = (
+    (__ \ "parts").write[Seq[Part]] and
+      (__ \ "role").writeNullable[ChatRole]
+  )(
+    // somehow unlift(Content.unapply) is not working in Scala3
+    (x: Content) => (x.parts, x.role)
+  )
+
+  implicit val contentReads: Reads[Content] = (
+    (__ \ "parts").readWithDefault[Seq[Part]](Nil) and
+      (__ \ "role").readNullable[ChatRole]
+  )(Content.apply(_: Seq[Part], _: Option[ChatRole]))
+
+  implicit val contentFormat: Format[Content] = Format(contentReads, contentWrites)
 
   // Tools
   implicit val toolPrefixFormat: Format[ToolPrefix] = enumFormat(ToolPrefix.values: _*)

google-gemini-client/src/test/scala/io/cequence/openaiscala/gemini/JsonFormatsSpec.scala

@@ -67,6 +67,19 @@ class JsonFormatsSpec extends AnyWordSpecLike with Matchers {
       )
     }
 
+    "deserialize candidate with empty content" in {
+      testDeserialization[Candidate](
+        Candidate(
+          content = Content.apply()
+        ),
+        """{
+          |  "content" : {},
+          |  "safetyRatings" : [ ],
+          |  "groundingAttributions" : [ ]
+          |}""".stripMargin
+      )
+    }
+
     "serialize and deserialize top candidate" in {
       prettyTestCodec[TopCandidates](
         TopCandidates(