Options: Validate named registrations

[aelij]

Background and Motivation

Currently the Options API will return a new instance of the options class even if it was not configured. This is especially problematic with named options, where a misconfiguration can easily occur. This is compounded by the fact that validation is configured per named instance. I suggest a way to validate that a named option has been explicitly registered.

Proposed API

namespace Microsoft.Extensions.Options
{
    public class OptionsBuilder<T> {
+        ValidateNames();
    }
}

Usage Examples

var services = new ServiceCollection();
services.AddOptions<MyOptions>().ValidateNames();
services.AddOptions<MyOptions>("X").Configure(o => { ... });
var serviceProvider = services.BuildServiceProvider();
var myOptions = serviceProvider.GetService<IOptionsMonitor<MyOptions>>();
myOptions.Get("X") // returns value
myOptions.Get("Y") // throws

Alternative Designs

Another option is to allow validations to be defined for all instances. Currently there's a ConfigureAll method that allows defining an action that would run on all named options, but no API to configure validation for all instances. So we could have something like AddAllOptions (not the best name, I know):

services.AddAllOptions<MyOptions>().ValidateDataAnnotations();

Risks

None - this behavior does not change existing options as it must be opted into.

[ghost]

Tagging subscribers to this area: @maryamariyan
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Issue Details

---

Background and Motivation

Currently the Options API will return a new instance of the options class even if it was not configured. This is especially problematic with named options, where a misconfiguration can easily occur. This is compounded by the fact that validation is configured per named instance. I suggest a way to validate that a named option has been explicitly registered.

Proposed API

namespace Microsoft.Extensions.Options
{
    public class OptionsBuilder<T> {
+        ValidateNames();
    }
}

Usage Examples

var services = new ServiceCollection();
services.AddOptions<MyOptions>().ValidateNames();
services.AddOptions<MyOptions>("X").Configure(o => { ... });
var serviceProvider = services.BuildServiceProvider();
var myOptions = serviceProvider.GetService<IOptionsMonitor<MyOptions>>();
myOptions.Get("X") // returns value
myOptions.Get("Y") // throws

-->

Alternative Designs

Another option is to allow validations to be defined for all instances. Currently there's a ConfigureAll method that allows defining an action that would run on all named options, but no API to configure validation for all instances. So we could have something like AddAllOptions (not the best name, I know):

services.AddAllOptions<MyOptions>().ValidateDataAnnotations();

Risks

None - this behavior does not change existing options as it must be opted into.

Author:	aelij
Assignees:	-
Labels:	api-suggestion, area-Extensions-Options, untriaged
Milestone:	-

[maryamariyan]

We added a new feature into .NET 6 Preview 2 for allowing options validation also for named options. For more information check out this original issue: #36391

Closing as fixed.

[aelij]

@maryamariyan I took a quick look at the PR and I don't think this use case is covered.

It's not about validating the options at start-up, it's validating that only pre-registered names can be used when calling IOptions<T>.Get(string).

An unconfigured named option is very hard to debug without this.

[davidfowl]

We would need to add another API for that. This one can't cover arbitrary names

[aelij]

@maryamariyan Could you please reopen the issue?

[davidfowl]

How would this work if all names aren't known up front?

[aelij]

In our use case all names are registered to the DI engine.

I experimented a bit, and it turns out the following works for validating all named options (the alternate design I suggested):

services.AddSingleton<IValidateOptions<MyOptions>>(new ValidateOptions<MyOptions>(null, o => Validate(o), "invalid"));
services.AddSingleton<IValidateOptions<MyOptions>>(new DataAnnotationValidateOptions<MyOptions>(null))

But the API is not easily discoverable (passing null as name). Maybe consider adding extension methods for the above?

[davidfowl]

I'm not sure I'm following... What works. Can you describe the end to end here?

[aelij]

The problem we had was that an unexpected name was used, which retrieved an unconfigured and unvalidated instance of an option.

I suggested 2 solutions (not mutually exclusive):

• Ensure that only names that were registered could be fetched from IOptionsMonitor<T>
• Enforce validation for all instances, whether pre-registered or not

The latter is possible with the above code sample.

[davidfowl]

Enforce validation for all instances, whether pre-registered or not

And this has nothing to do with validation on startup right?

[aelij]

Right. Validating this at start-up could be an added bonus.

[davidfowl]

Right. Validating this at start-up could be an added bonus.

Got it, this only works when you specify which names up front.