[Bug]: http-server-csharp: Generated model file fails to compile due to Unresolved Symbol: refkey

[abatishchev]

Describe the bug

Example:

// Generated by @typespec/http-server-csharp
// <auto-generated />
#nullable enable

using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Text.Json.Serialization;
using TypeSpec.Helpers;
using TypeSpec.Helpers.JsonConverters;

namespace Microsoft.MyRpNamespace;

/// <summary>
/// Azure API Key Authentication
/// </summary>
public partial class AzureApiKeyAuthentication
{
    /// <summary>
    /// API key authentication
    /// </summary>
    [JsonPropertyName("type")]
    public <Unresolved Symbol: refkey[sSymbol(emitter-framework:csharp)⁣o28]> Type { get; set; }

    /// <summary>
    /// location of the API key
    /// </summary>
    [JsonPropertyName("in")]
    public <Unresolved Symbol: refkey[sSymbol(emitter-framework:csharp)⁣o29]> In { get; set; }

    /// <summary>
    /// name of the API key
    /// </summary>
    [JsonPropertyName("name")]
    public string Name { get; } = "Ocp-Apim-Subscription-Key";
}

result in C# compiler errors:

• The name 'refkey' does not exist in the current context.
• The name 'sSymbol' does not exist in the current context.
• The name 'emitter' does not exist in the current context.
• The name 'framework' does not exist in the current context.

Reproduction

1. Use an ARM RP typespec
2. Add the following to tspconfig.yaml

emit:
  - "@typespec/http-server-csharp"
options:
  "@typespec/http-server-csharp":
    emitter-output-dir: "{project-root}/generated/{emitter-name}"
    output-type: all
    emit-mocks: none
    overwrite: true

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 @typespec/http-server-csharp emitter generates C# model files containing unresolved Alloy symbol placeholders (e.g., <Unresolved Symbol: refkey[sSymbol(emitter-framework:csharp)...]>) as property types, which cause C# compiler errors.

Category: Bug
Area: emitter:service:csharp

⚠️ No playground link applicable (this is a C# server emitter issue, not a TypeSpec language issue).

🔍 Analysis

The generated C# code contains raw Alloy framework symbol references that were not resolved to actual type names before file output. This indicates the emitter's symbol resolution step failed or was skipped for certain property types (in this case, enum-like types for type and in fields in AzureApiKeyAuthentication).

The placeholder format refkey[sSymbol(emitter-framework:csharp)o28] is an internal Alloy code generation framework artifact that should be replaced with the actual C# type reference during rendering.

Affected component: packages/http-server-csharp — likely in the model/property type rendering logic when handling security scheme or union/enum properties.

Potential root cause: The emitter may not be correctly resolving refkey references for certain TypeSpec types (possibly Azure-specific security scheme enums from ARM RP specs), resulting in raw symbol placeholders being emitted instead of resolved type names.

📝 Suggested next steps

• Identify which TypeSpec type maps to the type and in properties in AzureApiKeyAuthentication (likely a string enum or union)
• Trace the emitter code path for rendering property types in packages/http-server-csharp to find where refkey resolution fails
• Add a test case using an ARM RP spec with security scheme types to prevent regression

Generated by Agentic Triage