OpenApi: How to change model name?

[Thijmen]

Hi there,

First of all; I am loving the Dotnet 9 updates! I am diving right in and I have some difficulties regarding renaming model names.

Say the given scenario:

public static class SomeCommand {
    public record Command(string Name);
}

public static class SomeOtherCommand {
    public record Command(string Name);
}

I use these records as bodies in my APIs. When using the latest dotnet 9 openapi services, the model names end up as "Command", "Command2", "Command3" etc. Ideally, I would like some filter to change these.

This is what I have as of now:

public class CommandSchemaNameTransformer : IOpenApiSchemaTransformer
{
    public Task TransformAsync(OpenApiSchema schema, OpenApiSchemaTransformerContext context, CancellationToken cancellationToken)
    {
        if (context.JsonPropertyInfo == null)
        {
            var type = context.JsonTypeInfo.Type;
            var schemaType = typeof(SomeOtherCommand.Command);
            if (type == schemaType)
            {
                var fullName = schemaType.FullName;
                if (!string.IsNullOrWhiteSpace(fullName) && fullName.Contains("+"))
                {
                    var parts = fullName.Split('.');
                    var lastPart = parts[^1];
                    var commandParts = lastPart.Split('+');
                    schema.Title = string.Join("", commandParts);
                }
            }
        }
        
        return Task.CompletedTask;
    }
} 

This does update the title, but not the schema name:

Is what I want actually achievable?

[martincostello]

I believe that the OpenApiOptions.CreateSchemaReferenceId property is the extension point for this:

aspnetcore/src/OpenApi/src/Services/OpenApiOptions.cs

Lines 52 to 59 in eb68e01

	/// <summary>
	/// A delegate to determine how reference IDs should be created for schemas associated with types in the given OpenAPI document.
	/// </summary>
	/// <remarks>
	/// The default implementation uses the <see cref="CreateDefaultSchemaReferenceId"/> method to generate reference IDs. When
	/// the provided delegate returns <see langword="null"/>, the schema associated with the <see cref="JsonTypeInfo"/> will always be inlined.
	/// </remarks>
	public Func<JsonTypeInfo, string?> CreateSchemaReferenceId { get; set; } = CreateDefaultSchemaReferenceId;

[martincostello]

I would try the delegate property first, as it seems to be explicitly documented to be for that, rather than obliquely via a key in an annotation.

[Thijmen]

It is however used here too;

aspnetcore/src/OpenApi/src/Services/Schemas/OpenApiSchemaStore.cs

Line 217 in eb68e01

if (schema.Annotations?.TryGetValue(OpenApiConstants.SchemaId, out var referenceIdObject) == true

Let me take as swing at the delegate property.

[Thijmen]

@martincostello Too bad the .GetSchemaReferenceId method is not available for me. I'd like to only make changes if my class contains "Command", so I leave most stuff "per default". Any other suggestion here?

[martincostello]

You could check the name and if it isn't command you could use their default:

aspnetcore/src/OpenApi/src/Services/OpenApiOptions.cs

Line 26 in eb68e01

public static string? CreateDefaultSchemaReferenceId(JsonTypeInfo jsonTypeInfo) => jsonTypeInfo.GetSchemaReferenceId();

[Thijmen]

You are totally right, oversight from my side. Been busy upgrading a project since last night. Maybe time for some coffee :D Thanks for the help @martincostello, truly appreciated. Cheers!