Allow Property Replacement in Generated ClientSettings Using Custom Code

[jorgerangel-msft]

Consider this scenario where the generated Url setting property should be replaced with the one defined in custom code.

// CUSTOM
public partial class QueueClientSettings
{
    /// <summary> Gets or sets the Queue Uri. </summary>
    [CodeGenMember("Url")]
    public Uri QueueUri { get; set; }
}

This leads to code that doesn't compile instead:

// GENERATED
/// <summary> Represents the settings used to configure a <see cref="QueueClient"/> that can be loaded from an <see cref="IConfigurationSection"/>. </summary>
[Experimental("SCME0002")]
public partial class QueueClientSettings : ClientSettings
{
    /// <summary> Gets or sets the Options. </summary>
    public QueueClientOptions Options { get; set; }

    /// <summary> Binds configuration values from the given section. </summary>
    /// <param name="section"> The configuration section. </param>
    protected override void BindCore(IConfigurationSection section)
    {
        if (Uri.TryCreate(section["Url"], UriKind.Absolute, out Uri url))
        {
            this.Url = url;
        }
        string connectionString = section["ConnectionString"];
        if (!string.IsNullOrEmpty(connectionString))
        {
            ConnectionString = connectionString;
        }
        string queueName = section["QueueName"];
        if (!string.IsNullOrEmpty(queueName))
        {
            QueueName = queueName;
        }
        IConfigurationSection optionsSection = section.GetSection("Options");
        if (optionsSection.Exists())
        {
            Options = new QueueClientOptions(optionsSection);
        }
    }
}

We should honor any custom code replacements done in ClientSettings

[github-actions]

🎯 Issue Triage

When using [CodeGenMember("Url")] in custom code to replace a generated property on ClientSettings, the generated BindCore method still references this.Url (the original property name) rather than the replacement property QueueUri, causing a compilation error.

Category: Bug
Area: emitter:client:csharp

⚠️ No TypeSpec reproduction provided — this is a C# emitter customization issue (no playground link applicable).

🔍 Analysis

• Affected component: C# emitter — ClientSettings / BindCore generation logic
• Root cause: When generating the BindCore method, the emitter does not check whether a property has been replaced via [CodeGenMember]. It unconditionally emits this.Url instead of looking up the actual member name after custom code replacement is applied.
• Impact: Any SDK that uses [CodeGenMember] to rename a ClientSettings property will get generated code that fails to compile.
• The fix should check custom code member replacements when emitting property assignments in BindCore, using the replacement property name (QueueUri) in place of the original generated name (Url).

📝 Suggested next steps

• Locate the BindCore code generation logic in the C# emitter and identify where property references are emitted.
• Check if [CodeGenMember] replacements are already resolved for other generated methods; if so, apply the same resolution to BindCore.
• Add a test case: a ClientSettings subclass where Url is replaced via [CodeGenMember] and verify generated BindCore uses the replacement property name.

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