Drop file_size default in AttachmentDto and test null mapping

Author: gpunto

stream-chat-android-client/src/main/java/io/getstream/chat/android/client/api2/model/dto/AttachmentDto.kt

@@ -33,7 +33,7 @@ internal data class AttachmentDto(
     val author_name: String?,
     val author_link: String?,
     val fallback: String?,
-    val file_size: Int? = 0,
+    val file_size: Int?,
     val image: String?,
     val image_url: String?,
     val mime_type: String?,

stream-chat-android-client/src/test/java/io/getstream/chat/android/client/Mother.kt

@@ -750,7 +750,7 @@ internal object Mother {
         authorName: String? = randomString(),
         authorLink: String? = randomString(),
         fallback: String? = randomString(),
-        fileSize: Int = positiveRandomInt(),
+        fileSize: Int? = positiveRandomInt(),
         image: String? = randomString(),
         imageUrl: String? = randomString(),
         mimeType: String? = randomString(),

stream-chat-android-client/src/test/java/io/getstream/chat/android/client/api2/mapping/DomainMappingTest.kt

@@ -576,6 +576,16 @@ internal class DomainMappingTest {
         assertEquals(expected, attachment)
     }
 
+    @Test
+    fun `AttachmentDto with null file_size falls back to 0`() {
+        val attachmentDto = randomAttachmentDto(fileSize = null)
+        val sut = Fixture().get()
+        val attachment = with(sut) {
+            attachmentDto.toDomain()
+        }
+        assertEquals(0, attachment.fileSize)
+    }
+
     @Test
     fun `BannedUserResponse is correctly mapped to BannedUser`() {
         val bannedUserResponse = randomBannedUserResponse()