Merge

Author: emilypgoogle

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/Content.kt

@@ -88,8 +88,14 @@ constructor(public val role: String? = "user", public val parts: List<Part>) {
     @EncodeDefault val role: String? = "user",
     val parts: List<InternalPart>
   ) {
-
-    internal fun toPublic(): Content = Content(role, parts.map { it.toPublic() })
+    internal fun toPublic(): Content {
+      val returnedParts =
+        parts.map { it.toPublic() }.filterNot { it is TextPart && it.text.isEmpty() }
+      // If all returned parts were text and empty, we coalesce them into a single one-character
+      // string
+      // part so the backend doesn't fail if we send this back as part of a multi-turn interaction.
+      return Content(role, returnedParts.ifEmpty { listOf(TextPart(" ")) })
+    }
   }
 }