Failed to load API definition is displayed on the Swagger Generation page
Environment
| Product | Progress® Telerik® Reporting |
| Project Type | ASP.NET Core |
Description
Failed to load API definition. message is displayed on the Swagger Generation page(usually localhost:port/swagger).
There may also be a short error on the page about being unable to fetch swagger.json.
Error Message
- Error message on client-side:
Fetch error
response status is 500 https://localhost:{port}/swagger/v1/swagger.json
- Server-side exception when using
Swashbuckle:
An unhandled exception has occurred while executing the request.
Swashbuckle.AspNetCore.SwaggerGen.SwaggerGeneratorException: Conflicting method/path combination "GET api/ReportDesignerControllerBase" for actions - Telerik.WebReportDesigner.Services.Controllers.ReportDesignerControllerBase.GetDesignerResource (Telerik.WebReportDesigner.Services),Telerik.WebReportDesigner.Services.Controllers.ReportDesignerControllerBase.GetResource (Telerik.WebReportDesigner.Services). Actions require a unique method/path combination for Swagger/OpenAPI 3.0. Use ConflictingActionsResolver as a workaround
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperations(IEnumerable`1 apiDescriptions, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GeneratePaths(IEnumerable`1 apiDescriptions, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GetSwagger(String documentName, String host, String basePath)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
- Server-side exception when using
NSwag:
An unhandled exception has occurred while executing the request.
System.InvalidOperationException: The method 'get' on path '/api/ReportDesignerControllerBase' is registered multiple times.
at NSwag.Generation.AspNetCore.AspNetCoreOpenApiDocumentGenerator.AddOperationDescriptionsToDocument(OpenApiDocument document, Type controllerType, List`1 operations, OpenApiDocumentGenerator swaggerGenerator, OpenApiSchemaResolver schemaResolver)
at NSwag.Generation.AspNetCore.AspNetCoreOpenApiDocumentGenerator.GenerateApiGroups(OpenApiDocument document, IGrouping`2[] apiGroups, OpenApiSchemaResolver schemaResolver)
at NSwag.Generation.AspNetCore.AspNetCoreOpenApiDocumentGenerator.GenerateAsync(ApiDescriptionGroupCollection apiDescriptionGroups)
at NSwag.AspNetCore.Middlewares.OpenApiDocumentMiddleware.GenerateDocumentAsync(HttpContext context)
at NSwag.AspNetCore.Middlewares.OpenApiDocumentMiddleware.GetDocumentAsync(HttpContext context)
at NSwag.AspNetCore.Middlewares.OpenApiDocumentMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
Cause
There is a confliction method/path in ReportDesignerController. Swagger requires actions to have unique methods/paths.
Solution
Swashbuckle
- For .NET Core 3.1 and .NET 5, configure the Swagger Generation in Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
...
services.AddSwaggerGen(c => {
c.ResolveConflictingActions(apiDescriptions => apiDescriptions.First());
c.IgnoreObsoleteActions();
c.IgnoreObsoleteProperties();
c.CustomSchemaIds(type => type.FullName);
});
...
}
- For .NET 6+, configure the Swagger Generation in Program.cs
builder.Services.AddSwaggerGen(c => {
c.ResolveConflictingActions(apiDescriptions => apiDescriptions.First());
c.IgnoreObsoleteActions();
c.IgnoreObsoleteProperties();
c.CustomSchemaIds(type => type.FullName);
});
NSwag
Implement the NSwag.Generation.Processors.IOperationProcessor interface as follows and then use it in the AddSwaggerGen configuration:
public class IncludeControllersInSwagger : IOperationProcessor
{
public bool Process(OperationProcessorContext context)
{
return ShouldIncludeController(context.ControllerType);
}
bool ShouldIncludeController(System.Type type)
{
return !(type.AssemblyQualifiedName == typeof(Telerik.WebReportDesigner.Services.Controllers.ReportDesignerControllerBase).AssemblyQualifiedName);
}
}
- For .NET Core 3.1 and .NET 5, configure the Swagger Generation in Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
...
services.AddSwaggerGen(c => {
c.IgnoreObsoleteProperties = true;
c.OperationProcessors.Add(new IncludeControllersInSwagger());
});
...
}
- For .NET 6+, configure the Swagger Generation in Program.cs
builder.Services.AddSwaggerGen(c => {
c.IgnoreObsoleteProperties = true;
c.OperationProcessors.Add(new IncludeControllersInSwagger());
});