Update isOffline(errorCode:) to catch additional NSURLError

[jncosideout]

PR Description

The app was not saving scanned barcodes when offline/no internet connectivity. I added an error code to be checked for verifying offline status.

I tested the offline scan by setting my device to airplane mode and scanning a food product.
This throws to the onError callback (line 442) of dataManager.getProduct(byBarcode:) inside ScannerViewController.getProduct(barcode: ...)

The next line checks isOffline(errorCode:) and if true, we call handleGetProductSuccess(barcode: ...)
According to the comment in the source code, this is when we:
//Assume product does not exist and store locally for later upload

For me, the error code passed is -1004 "Could not connect to the server." According to my research, that matches NSURLErrorCannotConnectToHost

My only concern is that there are other NSURLErrors or other errors that would be thrown when offline or when connectivity is bad. isOffline(errorCode:) should anticipate all possible such error codes.

Type of Changes

• Fixes Issue Offline scans are not logged to history #267
• New feature

Checklist

• If you have multiple commits please combine them into one commit by squashing them.
• Code is well documented
• Included unit tests for new functionality
• All user-visible strings are made translatable
• Code passes Travis builds in your branch

[philippeauriach]

As we are touching those, we might want to add more cases to "no internet connection" test ?
The full list of errors is listed here : https://developer.apple.com/documentation/cfnetwork/cfnetworkerrors

I think we should go for those (open to discussion) :
kCFURLErrorCannotFindHost
kCFURLErrorCannotConnectToHost
kCFURLErrorNetworkConnectionLost
kCFURLErrorDNSLookupFailed
kCFURLErrorInternationalRoamingOff
kCFURLErrorCallIsActive
kCFURLErrorDataNotAllowed

[jncosideout]

As we are touching those, we might want to add more cases to "no internet connection" test ?

That is exactly what I'm thinking. I will include them into isOffline(errorCode:) and re-submit my PR.

I checked the CFNetworkErrors you listed, each one corresponds to an NSURLError and they have the same raw values.
Therefore, I shouldn't need to re-cast the error into a CFNetworkError before passing them to isOffline(errorCode:)

But how do I test those scenarios to throw the particular errors? Most of them seem out of my control so I don't know how to replicate them, e.g. "CannotFindHost", "InternationalRoamingOff", "CannotConnectToHost"
Also, my testing devices do not have cellular plans. So they're WiFi only.

[Update] I downloaded the [Apple Developer Tools ](Network Link Conditioner) Network Link Conditioner to simulate bad connections.

[jncosideout]

I wasn't able to trigger all the newly included network errors while testing, but I can confirm that func isOffline(:errorCode) will recognize when the device has no connection to the internet, because the error that is thrown when the device in airplane mode (CannotConnectToHost -1004) has been included.

[teolemon]

Thank you @jncosideout and @philippeauriach for the review 👍