Passing an empty string as the value for labelFilter in AzureAppConfigurationOptions.Select retrieves key-values in all labels.

[jimmyca15]

This unexpected behavior was originally described here.

As shown in this line, the Azure App Configuration provider prevents querying key-values from all labels since it can result in indeterministic configuration sets.

The configuration provider checks if label filter contains the * character, but it does not check if label filter is an empty string, which also selects key-values in all labels.

Example code:

    options.Select(KeyFilter.Any, "");

Expected:
Selects key-values with single label, same as passing null.

Actual:
Selects key-values with all labels

[jimmyca15]

Also repros with whitespace.