Azure
[azappconfig] Support LabelFilter.Null
Feature Request
I am using Dapr to connect to Azure AppConfig (https://github.com/dapr/components-contrib/tree/main/configuration/azure/appconfig) which uses this library behind the scenes and am trying to replicate the functionality described here https://learn.microsoft.com/en-us/azure/azure-app-configuration/howto-best-practices#key-value-compositions where you can request only config items that have a null label (I don't care about the .Select(... chaining in the example, I'm fine w/ making multiple queries myself).
The linked page on learn.microsoft.com references the LabelFilter.Null value, but I can't tell what that value is converted to behind the scenes; I have tried passing in "Null", "null", "LabelFilter.Null", "" and "(No label)" as label values and none of those return any values, so I assume they are just looking for those specific labels as opposed to the null label.
If there is/could be a string value I could pass in as a label that would trigger the "only items with null label" filtering that would be sufficient for my purposes.
@maffin-sa I stumbled across your issue when looking to file one of my own. I'm able to use this URL to send an HTTP request to Dapr and fetch only those configs without a label: http://localhost:3500/v1.0/configuration/azureappconfig?metadata.label=%00
Does that suffice for your problem?
@tlund101 Thanks for the suggestion, I wasn't able to get this to work w/ my current implementation (I'm guessing the Dapr .NET wrapper is modifying the value in some way so it's not getting through as just the null token, but I need to poke around in that source code a bit more), but if that functionality works for you, then this issue could probably be closed, although it might be nice for this library to have a dedicated "LabelFilter.Null" type value or at least mention in the docs that the label "%00" is what you want to use if you want to find all docs w/ a null label.
@maffin-sa @tlund101 passing string \x00 to labelFilter should work, it represents NULL char ASCII in Golang. It's indeed confusion leading, LabelFilter.Null in .net SDK is also this value, we should have pre-defined variable in Go as well.
