[Bug]: http-server-csharp: ProvisioningState is object

[abatishchev]

Describe the bug

Earlier, the ProviderHub package generated ProvisioningState as a struct with a field for every value defined in the spec:

[JsonConverter(typeof(EnumJsonConverter<ProvisioningState>))]
public readonly partial struct ProvisioningState
{
    public static readonly ProvisioningState Succeeded = "Succeeded", Failed = "Failed", Canceled = "Canceled", Accepted = "Accepted", Creating = "Creating", Updating = "Updating", Deleting = "Deleting";
}

Now, the http-server-csharp package generate it as an System.Object:

public partial class ThrottlingAccountProperties
{
    [JsonPropertyName("provisioningState")]
    public object ProvisioningState { get; set; }
}

public partial class ThrottlingAccount : TrackedResource
{
    [JsonPropertyName("properties")]
    public ThrottlingAccountProperties Properties { get; set; }
}

Reproduction

Any ARM/RPaaS RP's spec

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[github-actions]

🎯 Issue Triage
The C# service emitter regressed ARM/RPaaS model generation: ProvisioningState previously had a strongly typed extensible-enum representation but is now emitted as System.Object.
Category: Bug
Area: emitter:service:csharp

⚠️ No reproduction provided. A minimal repro would help diagnose this issue.

🔍 Analysis

The affected component is @typespec/http-server-csharp, specifically model type generation for the ARM common ProvisioningState shape. The generated property loses all known values and compile-time typing by falling back to object. This may indicate that the emitter does not recognize or lower the relevant ARM string union/extensible-enum shape, but the root cause cannot be confirmed without the source TypeSpec and package versions. Searches for ProvisioningState, extensible-enum fallback, and ARM/RPaaS enum generation found no issue describing the same failure.

📝 Suggested next steps

• Provide a minimal TypeSpec model that produces the object property.
• Include the previous and current @typespec/http-server-csharp versions to bound the regression.
• Add a service-emitter regression test asserting a strongly typed ProvisioningState property and its known values.

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