Accept null file_size in direct attachment parser

The direct AttachmentAdapter (used by the opt-in fast event parser added
on v6) was still calling reader.nextInt() for file_size, which throws on
explicit null. Coalesce to 0 to match the DTO + DomainMapping behavior.

Author: gpunto

stream-chat-android-client/src/main/java/io/getstream/chat/android/client/parser2/direct/AttachmentAdapter.kt

@@ -54,7 +54,7 @@ internal class AttachmentAdapter : JsonAdapter<Attachment>() {
                 "author_name" -> authorName = JsonParsingUtils.readNullableString(reader)
                 "author_link" -> authorLink = JsonParsingUtils.readNullableString(reader)
                 "fallback" -> fallback = JsonParsingUtils.readNullableString(reader)
-                "file_size" -> fileSize = reader.nextInt()
+                "file_size" -> fileSize = JsonParsingUtils.readNullableInt(reader) ?: 0
                 "image" -> image = JsonParsingUtils.readNullableString(reader)
                 "image_url" -> imageUrl = JsonParsingUtils.readNullableString(reader)
                 "mime_type" -> mimeType = JsonParsingUtils.readNullableString(reader)

stream-chat-android-client/src/test/java/io/getstream/chat/android/client/parser2/AttachmentParsingTest.kt

@@ -16,7 +16,6 @@
 
 package io.getstream.chat.android.client.parser2
 
-import com.squareup.moshi.JsonDataException
 import io.getstream.chat.android.client.api2.mapping.DomainMapping
 import io.getstream.chat.android.client.api2.model.dto.AttachmentDto
 import io.getstream.chat.android.client.parser2.direct.AttachmentAdapter
@@ -26,7 +25,6 @@ import io.getstream.chat.android.models.NoOpMessageTransformer
 import io.getstream.chat.android.models.NoOpUserTransformer
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertThrows
 
 internal class AttachmentParsingTest {
 
@@ -92,20 +90,19 @@ internal class AttachmentParsingTest {
 
     // endregion
 
-    // region file_size: null (non-nullable Int — both paths must throw)
+    // region file_size: null — coalesces to 0 on both paths
 
     @Test
-    fun `DTO path - throws on file_size null`() {
-        assertThrows<JsonDataException> {
-            parser.fromJson(AttachmentTestData.jsonWithFileSizeNull, AttachmentDto::class.java)
-        }
+    fun `DTO path - file_size null coalesces to 0`() {
+        val dto = parser.fromJson(AttachmentTestData.jsonWithFileSizeNull, AttachmentDto::class.java)
+        val attachment = with(domainMapping) { dto.toDomain() }
+        assertEquals(0, attachment.fileSize)
     }
 
     @Test
-    fun `Direct path - throws on file_size null`() {
-        assertThrows<JsonDataException> {
-            attachmentAdapter.fromJson(AttachmentTestData.jsonWithFileSizeNull)
-        }
+    fun `Direct path - file_size null coalesces to 0`() {
+        val attachment = attachmentAdapter.fromJson(AttachmentTestData.jsonWithFileSizeNull)
+        assertEquals(0, attachment?.fileSize)
     }
 
     // endregion