Allow Notification images without proper path extensions

[akivab]

Environment

• Xcode version: Version 12.0.1 (12A7300)
• Firebase SDK version: 6.33.0
• Firebase Component: Messaging
• Component version: 6.33.0
• Installation method: CocoaPods

Problem

Firebase Messaging does not seem to allow for image URLs without an extension that matches MIME type, despite the fact that we may be able to produce the right extension from the MIME type.

In the function

- (void)loadAttachmentForURL:(NSURL *)attachmentURL
           completionHandler:(void (^)(UNNotificationAttachment *))completionHandler {

We create the extension for the local download using

        NSString *suggestedPathExtension = [response.suggestedFilename pathExtension];

Which raises issues later in the function, i.e.

            FIRMessagingLoggerError(
                                    kFIRMessagingServiceExtensionLocalFileNotCreated,
                                    @"Failed to move the image file to local location: %@, error: %@\n", localURL,
                                    error);

Steps to reproduce:

What happened? How can we make the problem occur?

Create a notification with a URL that points to an image resource without the proper extension (e.g. a UUID)

Relevant Code:

Fixed the issue by changing the logic to

        NSString *suggestedPathExtension = [response.suggestedFilename pathExtension];
        NSString *mimeTypePathExtension = [response.MIMEType stringByReplacingOccurrencesOfString:@"image/" withString:@""];
        NSString *pathExtension = ((suggestedPathExtension.length > 0) ? suggestedPathExtension : mimeTypePathExtension);
        NSString *fileExtension = [NSString stringWithFormat:@".%@", pathExtension];