Swashbuckle.aspnetcore: Swagger ignores route parameter constraint

[antonGritsenko]

Swashbuckle.AspNetCore 4.0.1

We using route constraint to define some parameters (mainly guid).

This work fine with swagger if parameter defined at method parameter:

[HttpGet("User({id:guid})")]
public async Task<IActionResult> GetUserById(Guid id)

This will produce correct type and format:

"parameters": [
{
"type": "string",
"name": "id",
"in": "path",
"required": true,
"format": "guid"
}
]

But it does not work if method parameter omitted:

[HttpGet("User({id:guid})")]
public async Task<IActionResult> GetUserById()

This will produce type only, but not the format:

"parameters": [
{
"type": "string",
"name": "id",
"in": "path",
"required": true
}
]

Is this by design? How can we workaround this?

PS this is mainly used for custom OData implementation when parameters parsed inside ODataParser

[antonGritsenko]

For a moment I have found following workaround:

public class GuidParameterFilter : IParameterFilter
    {
        /// <inheritdoc />
        public void Apply(IParameter parameter, ParameterFilterContext context)
        {
            if (context.PropertyInfo == null && 
                parameter is NonBodyParameter nonBodyParam &&
                context.ApiParameterDescription.RouteInfo?.Constraints != null && 
                context.ApiParameterDescription.RouteInfo.Constraints.Any(c => c is GuidRouteConstraint))
            {
                nonBodyParam.Format = "guid";
            }
        }
    }

[knoxi]

same here, but for type int.
I also used your workarount until it's fixed in Swagger generation.

[lucianoac]

I was looking at this issue and came up with something:

//SwaggerGenerator.cs - GenerateParameter(...)

var parameterType = (apiParameter.ModelMetadata != null)
    ? apiParameter.ModelMetadata.ModelType
    : apiParameter.RouteInfo?.Constraints
        .Where(x => RouteConstraintMap.ContainsKey(x?.GetType()))
        .Select(x => RouteConstraintMap[x.GetType()])
        .FirstOrDefault();

var schema = (parameterType != null)
    ? _schemaGenerator.GenerateSchema(parameterType, schemaRepository)
    : new OpenApiSchema { Type = "string" };

(...)

private static readonly Dictionary<Type, Type> RouteConstraintMap = new Dictionary<Type, Type>
{
    { typeof(BoolRouteConstraint), typeof(bool) },
    { typeof(DateTimeRouteConstraint), typeof(DateTime) },
    { typeof(DecimalRouteConstraint), typeof(decimal) },
    { typeof(DoubleRouteConstraint), typeof(double)},
    { typeof(FloatRouteConstraint), typeof(float) },
    { typeof(GuidRouteConstraint), typeof(Guid) },
    { typeof(LongRouteConstraint), typeof(long) }
};

It's seem to do the trick. Now I'm trying to find out how to write a proper test to it. It look like the method CreateActionDescriptor(...) doens´t generate the constraint parameter. I'll keep looking for the solution but if someone could give me hint it would be nice. Any ideas @domaindrivendev ?

[DaleyKD]

Any update on this? I've got a controller that uses a GUID accountID as part of the route, and it's not in any of the actions directly, but is necessary.