Rich Push Attachment Problem using UNNotificationServiceExtension

Problem in notification service extension when we modify the content by adding an attchment to it.

Before we decided to publish this project, we tried everything that came into our minds, but unfortunately without success.

References

We also participated in Apple's forum where people also complained about this issue.

Issue

Our app uses UNNotificationServiceExtension to handle and modify rich content. We have an issue when we send a rich push with an image attachment, but it is reproducable only if you do a clean install of the app and reboot your device. The first push message the device receieves does not show the image and falls back to default message, discarding all other changes in content we did in our notification service extension.

When we send the same message again, everything works as expected, showing modified content in service extension and the image attachment.

Important note: The problem exists only if we change contnent's attachment. If we remove it and change other fields like title, subtitle, body, everything works as expected.

Requirements

Xcode 8.x
iOS 10.x device
push certificate
some pusher app - we used this

How To Reproduce

Perform clean install on a device (if the app was previously installed, delete it).
Run the app from Xcode
Allow notifications
In Xcode console you will find a "Push Token". Copy it.
Close the app - stop it.
Reboot the device.
Send a push
When you receive it on the device, you will see there is no attached image and title/subtitle/body are not modified.

Key step to reproduce it is to reboot your device. Problem exists regardless you've just installed the app on rebooted device, or run the app after device rebooted.

In step 8, we expect a message with attachment and modified title/subtitle/body, but we receive "original" message.

When same message is sent again, it is received as expected.

Push Payload

{
    "aps" : {
        "alert" : {
            "title" : "Original-Title",
            "subtitle" : "Original-Subtitle",
            "body" : "Original-Body"
        },
        "badge" : 1,
        "sound" : "default",
        "category" : "DefaultCategory",
        "mutable-content" : 1
    },
    "attachment" : "https://cdn0.iconfinder.com/data/icons/customicondesignoffice5/128/attachment.png"
}

You can use as attachment value any downloadable image - max size is 10 MB.

Our Observation

It seems to us there is some inter process communication problem when a device is rebooted. didReceive method from service extension runs in a separate process than main app and also in a background thread.

As stated in Apple's documentation for UNNotificationAttachment:

The system validates the content of attached files before scheduling the corresponding notification request. If an attached file is corrupted, invalid, or of an unsupported file type, the notification request is not scheduled for delivery. Once validated, attached files are moved into the attachment data store so that they can be accessed by the appropriate processes. Attachments located inside an app’s bundle are copied instead of moved.

the system moves/copies the attachment. It seems to us there is some problem during the process of moving/coping, assign IPC rights, validating it. It fails, and the message is delivered without modified content.

Why it shows original content is probably because the whole modified content becomes invalid because of the attachment. As stated in Apple's documentation for didReceive:

You can modify any of the content from the original request. You might customize the content for the current user or replace it altogether. You can use this method to download images or movies and add them as attachments to the content. You may also modify the alert text as long as you do not remove it. If the content object does not contain any alert text, the system ignores your modifications and delivers the original notification content.

Because of attachment, the whole content object is invalid, which means there is no alert text, and the system delivers the original notification content.

Maybe this is just a guess, but we hope Apple or someone else can help.

Who we are?

www.appculture.com

Thank you for any contribution to this issue! If you need more info, don't hesitate to contact us. We will appreciate it a lot.

appculture / RichNotificationAttachmentProblem