Feature names with colon in name are not parsed correctly

[peterwurzinger]

Given the following configuration:

"FeatureManagement": {
    "Feature1": true,
    "Prefix:Feature2": true
}

Querying the features was a bit surprising at first:

featureManager.IsEnabledAsync("Feature1") //returns true
featureManager.IsEnabledAsync("Prefix:Feature2") //returns false

Listing the feature names is also quite misleading:

featureManager.GetFeatureNamesAsync(); //returns "Feature1", "Prefix"

By taking a closer look, the colon is of course not only a gimmick, but more like a common separator for config sections. So when using the JSON file provider, the abovementioned configuration could also be semantically identical rephrased as

"FeatureManagement": {
    "Feature1": true,
    "Prefix": {
        "Feature2": true
    }
}

And that explains the weird behavior.

To solve that, would it be a possible to tokenize given feature names by : , treating them as config-sections and only the last segment as the name? Imho that would fix the "Prefix":Feature" : true case, as well as enable feature grouping (see above).

[jimmyca15]

In general, the ':' character should be avoided in setting names in json settings files in .NET Core. The ':' character is treated specially as you have called out. I don't think it would be a good idea to go against that concept. It may be a good idea to call this out in the readme though.

[peterwurzinger]

Well, since IsEnabledAsync("Prefix:Feature") will never behave as expected, would it then be an option to throw an exception, if the input string contains a colon?

[jimmyca15]

That's a great suggestion. Technically if someone is using a custom IFeatureDefinitionProvider then colon might be fine for them, but if the default ConfigurationFeatureDefinitionProvider is being used then we can throw an ArgumentException to prevent confusion in a case like this.

[cwe1ss]

I just tried Azure App Configuration and was surprised by this behavior as well. The docs use a colon for regular key/value pairs and this works as expected with ASP.NET Core ( https://learn.microsoft.com/en-us/azure/azure-app-configuration/quickstart-aspnet-core-app?tabs=core6x#create-an-app-configuration-store ) so I expected this to work with Feature Management as well.

It was even more unexpected that I had to use FeatureManagement:MyPrefix instead of just MyPrefix to get this working.

builder.Services.AddFeatureManagement(builder.Configuration.GetSection("FeatureManagement:MyPrefix"));

I think it would be important that we could use the same separator for regular keys and for flags when using Feature Management with Azure App Configuration.

[zhiyuanliang-ms]

#288
Resolved.