Fix error management

[defagos]

As a user I want errors to be reported to me in the best possible way.

Context

The final 16.1 broke error management again. Now error messages ask to look at the error log, where probably the real error can be found.

Acceptance criteria

• Errors are correctly reported on iOS and tvOS 16.1.
• Error management is improved further.
• Tests verify the identity of the errors.

Tasks

• [x] Improve error comparison and update error-checking UTs (cast to NSError and compare domain, code and localized string).
• [x] Look at the error log and extract errors there if reliable.
• [x] Verify if NSError wrapping is still required or if errors can be reliably forwarded no matter the code or their type.
• [x] Improve error management by listening to failed item playback notifications, i.e. AVPlayerItemFailedToPlayToEndTimeNotification. The error is in the associated userInfo dictionary.
• [x] Check errors raised in playlists (correct error message displayed to the user). Possible when navigating back to a failing item.
• [x] Check network errors.
• [x] Check on various devices and with different languages.
• [x] Improve error management in playlists when navigating back (open playlist example containing errors, the 2nd failing item is skipped when navigating forward but not backward).
• [x] Check memory profile.

Other non-related tasks found during development:

• [x] Time stability when returning to a partially played item in a playlist (likely need to prepend the periodic time publisher with the item current time). Increasing the tick to 5 seconds might also help understanding what happens during the transition between two items.
• [x] Fix test stream cleanup issue (DVR playlist sometimes made of chunks from an older test session).

[defagos]

I guess we need to extract the error information from the errorLog() if available. Any other attempt I made was unsuccessful. Fortunately all information is available in the log and requires minimal parsing to be converted back to an error.

We should likely not subscribe to AVPlayerItemNewErrorLogEntryNotification, though, since we don't want to respond to errors which might be logged during playback (e.g. temporary network failure). For item errors we are only interested in looking at the error log when the item status changes to .failed. If no log entries are available we can fallback on the item error.

[defagos]

Best practices were discussed in a WWDC talk.

[defagos]

There is a bug with the error log when navigating back to a failed item in a queue (i.e. replacing the current item with an item which previously failed). The error log is cleared so that we cannot access detailed information (even if the item error property says to look at the error log).

I attempted to write a unit test but without success. The obvious solution is to cache the error when extracted the first time using an associated object.

To reproduce:

• Open the playlist example with error.
• Move forward after the failing item.
• Navigate back.

Sometimes (very often) the friendly error message is lost. If not repeat.

Note that the failing item should be skipped later (see todo list above) but the fix is still relevant IMHO (though it is a shame we cannot write a good unit test for it).

[defagos]

Test stream cleanup was really buggy. As a result the DVR stream would get messy if older chunks still existed. Two issues with the cleanup code:

• The criterium to look for matching processes was wrong.
• We should wait for the processes to disappear before cleaning the directory (safer).

I suspect this incorrect cleanup might explain the reliability issues we had on the CI server.

[defagos]

NSError wrapping is really required when passing errors to the resource loader, otherwise the result is unreliable (works in the simulator but not on device). Easy to check by removing wrapping from finishLoadingReliably(with:) implementation and checking the demo error examples.

[defagos]

Here is a way to have a .AVPlayerItemFailedToPlayToEndTime being emitted:

1. Start playback for DVR content.
2. Enable airplane mode during playback.
3. Wait > 2 minutes (timeout).

We can therefore improve our item state management, though adding a unit test for this specific case is out of question.

[defagos]

~Depending on the language (currently the demo declares English as language) error messages returned by AVPlayer or our own messages are localized differently, e.g. in case of network errors. On a device in French we have:~

• ~Attempting to play a URL without network connection: French message (i.e. device language). Returned by AVPlayer which loads the resource directly.~
• ~Attempting to play a URN without network connection: French message (i.e. bundle language). Returned by the resource loader which gets this error from URLSession (not an HTTP error we build).~

~Adding language files for French fixes this inconsistency (in this example files in en.lproj and fr.lproj). I will create another issue to add dummy language files to all packages and the demo since this is not in the scope of the present task.~

Update: I uninstalled the app and installed it again. The bundle might have been messed up.