Merge pull request #341 from xmtp/ar/empty-fallbacks

fix: Correctly handle empty/undefined fallbacks

android/src/main/java/expo/modules/xmtpreactnativesdk/wrappers/DecodedMessageWrapper.kt

@@ -13,14 +13,19 @@ class DecodedMessageWrapper {
             return gson.toJson(message)
         }
 
-        fun encodeMap(model: DecryptedMessage): Map<String, Any> = mapOf(
-            "id" to model.id,
-            "topic" to model.topic,
-            "contentTypeId" to model.encodedContent.type.description,
-            "content" to ContentJson(model.encodedContent).toJsonMap(),
-            "senderAddress" to model.senderAddress,
-            "sent" to model.sentAt.time,
-            "fallback" to model.encodedContent.fallback
-        )
+        fun encodeMap(model: DecryptedMessage): Map<String, Any?> {
+            // Kotlin/Java Protos don't support null values and will always put the default ""
+            // Check if there is a fallback, if there is then make it the set fallback, if not null
+            val fallback = if (model.encodedContent.hasFallback()) model.encodedContent.fallback else null
+            return mapOf(
+                "id" to model.id,
+                "topic" to model.topic,
+                "contentTypeId" to model.encodedContent.type.description,
+                "content" to ContentJson(model.encodedContent).toJsonMap(),
+                "senderAddress" to model.senderAddress,
+                "sent" to model.sentAt.time,
+                "fallback" to fallback
+            )
+        }
     }
 }

example/src/tests.ts

@@ -31,6 +31,20 @@ const ContentTypeNumber: ContentTypeId = {
   versionMinor: 0,
 }
 
+const ContentTypeNumberWithUndefinedFallback: ContentTypeId = {
+  authorityId: 'org',
+  typeId: 'number_undefined_fallback',
+  versionMajor: 1,
+  versionMinor: 0,
+}
+
+const ContentTypeNumberWithEmptyFallback: ContentTypeId = {
+  authorityId: 'org',
+  typeId: 'number_empty_fallback',
+  versionMajor: 1,
+  versionMinor: 0,
+}
+
 export type NumberRef = {
   topNumber: {
     bottomNumber: number
@@ -66,6 +80,20 @@ class NumberCodec implements JSContentCodec<NumberRef> {
   }
 }
 
+class NumberCodecUndefinedFallback extends NumberCodec {
+  contentType = ContentTypeNumberWithUndefinedFallback
+  fallback(content: NumberRef): string | undefined {
+    return undefined
+  }
+}
+
+class NumberCodecEmptyFallback extends NumberCodec {
+  contentType = ContentTypeNumberWithEmptyFallback
+  fallback(content: NumberRef): string | undefined {
+    return ''
+  }
+}
+
 const LONG_STREAM_DELAY = 20000
 
 export type Test = {
@@ -1184,6 +1212,62 @@ test('correctly handles lowercase addresses', async () => {
   return true
 })
 
+test('handle fallback types appropriately', async () => {
+  const bob = await Client.createRandom({
+    env: 'local',
+    codecs: [
+      new NumberCodecEmptyFallback(),
+      new NumberCodecUndefinedFallback(),
+    ],
+  })
+  const alice = await Client.createRandom({
+    env: 'local',
+  })
+  bob.register(new NumberCodecEmptyFallback())
+  bob.register(new NumberCodecUndefinedFallback())
+  const bobConvo = await bob.conversations.newConversation(alice.address)
+  const aliceConvo = await alice.conversations.newConversation(bob.address)
+
+  await bobConvo.send(12, { contentType: ContentTypeNumberWithEmptyFallback })
+
+  await bobConvo.send(12, {
+    contentType: ContentTypeNumberWithUndefinedFallback,
+  })
+
+  const messages = await aliceConvo.messages()
+  assert(messages.length === 2, 'did not get messages')
+
+  const messageUndefinedFallback = messages[0]
+  const messageWithDefinedFallback = messages[1]
+
+  let message1Content = undefined
+  try {
+    message1Content = messageUndefinedFallback.content()
+  } catch {
+    message1Content = messageUndefinedFallback.fallback
+  }
+
+  assert(
+    message1Content === undefined,
+    'did not get content properly when empty fallback: ' +
+      JSON.stringify(message1Content)
+  )
+
+  let message2Content = undefined
+  try {
+    message2Content = messageWithDefinedFallback.content()
+  } catch {
+    message2Content = messageWithDefinedFallback.fallback
+  }
+
+  assert(
+    message2Content === '',
+    'did not get content properly: ' + JSON.stringify(message2Content)
+  )
+
+  return true
+})
+
 test('instantiate frames client correctly', async () => {
   const frameUrl =
     'https://fc-polls-five.vercel.app/polls/01032f47-e976-42ee-9e3d-3aac1324f4b8'

ios/Wrappers/DecodedMessageWrapper.swift

@@ -5,14 +5,17 @@ import XMTP
 // into react native.
 struct DecodedMessageWrapper {
 	static func encodeToObj(_ model: XMTP.DecryptedMessage, client: Client) throws -> [String: Any] {
+    // Swift Protos don't support null values and will always put the default ""
+    // Check if there is a fallback, if there is then make it the set fallback, if not null
+		let fallback = model.encodedContent.hasFallback ? model.encodedContent.fallback : nil
 		return [
 			"id": model.id,
 			"topic": model.topic,
 			"contentTypeId": model.encodedContent.type.description,
 			"content": try ContentJson.fromEncoded(model.encodedContent, client: client).toJsonMap() as Any,
 			"senderAddress": model.senderAddress,
 			"sent": UInt64(model.sentAt.timeIntervalSince1970 * 1000),
-			"fallback": model.encodedContent.fallback,
+			"fallback": fallback,
 		]
 	}
 

src/lib/DecodedMessage.ts

@@ -1,13 +1,11 @@
+import { Buffer } from 'buffer'
+
 import { Client } from './Client'
 import {
-  ContentCodec,
   JSContentCodec,
   NativeContentCodec,
   NativeMessageContent,
 } from './ContentCodec'
-import { ReplyCodec } from './NativeCodecs/ReplyCodec'
-import { TextCodec } from './NativeCodecs/TextCodec'
-import { Buffer } from 'buffer'
 
 const allowEmptyProperties: (keyof NativeMessageContent)[] = [
   'text',
@@ -81,7 +79,8 @@ export class DecodedMessage<ContentTypes = any> {
     this.senderAddress = senderAddress
     this.sent = sent
     this.nativeContent = content
-    this.fallback = fallback
+    // undefined comes back as null when bridged, ensure undefined so integrators don't have to add a new check for null as well
+    this.fallback = fallback ?? undefined
   }
 
   content(): ContentTypes {