Missing properties in ARTErrorInfo

[ikbalkaya]

Captured in following Flutter issue
ably/ably-flutter#14

Following properties are missing from ARTErrorInfo class

• code
• cause

Please see linked issue for details of each property

┆Issue is synchronized with this Jira Story by Unito

[maratal]

• code - this one inherited from NSError
• cause - I guess it's a reason in ARTErrorInfo, unless docs give no room for the platform specific implementation it can be kept as is. WDYT @ikbalkaya @lawrence-forooghian @lukasz-szyszkowski @QuintinWillison

[QuintinWillison]

From TI1 and the IDL, we can see that cause is an optional ErrorInfo instance. The reason property on ARTErrorInfo is a string, so not the same thing.

Therefore, perhaps, cause is more aligned with one, other or both of:

• the NSUnderlyingErrorKey, used for NSError's userInfo property
• NSError's underlyingErrors property

Perhaps one of the corners of Apple's APIs that could best be described as a bit of a 'hot mess' (not unlike our own ErrorInfo 'concept', but I digress 🙄)... so, I think to fix this issue:

1. We need to add a cause issue to ARTErrorInfo, of type ARTErrorInfo
2. Work out an appropriate algorithm for populating it... do we have any existing examples of where it might have revealed something interesting that we can model on?

[maratal]

...and the IDL, we can see that cause is an optional ErrorInfo instance.

You are right, my bad.

[maratal]

Work out an appropriate algorithm for populating it...

From the docs to NSUnderlyingErrorKey:

The corresponding value is an error that was encountered in an underlying implementation and caused the error that the receiver represents to occur.

Seems like the NSUnderlyingErrorKey is a perfect match for cause property.