How to turn on CircuitOptions.DetailedErrors?

More digging on this revealed that there are both non-Blazor specific .NET Core ways to turn on Detailed Errors, and also a Blazor specific approach:

The general .NET Core way to turn on Detailed Errors:

There are a number of ways to get the detailed errors as discussed in the .NET Core documentation, but I ended up using the Detailed Errors setting:

WebHost.CreateDefaultBuilder(args).UseSetting(WebHostDefaults.DetailedErrorsKey, "true")

And the Development Environment setting:

WebHost.CreateDefaultBuilder(args).UseEnvironment(Environments.Development)

Both of those are used in Program.cs:

If you are using the older (and eventually to be deprecated IWebHostBuilder approach) that looks like this:

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseSetting(WebHostDefaults.DetailedErrorsKey, "true")
        //.UseEnvironment(EnvironmentName.Development)
        .UseStartup<Startup>();

And if you’re using the newer IHostBuilder approach that was introduced with Core 2.1 that looks like this:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder
                .UseStartup<Startup>()
                .UseSetting(WebHostDefaults.DetailedErrorsKey, "true")
                //.UseEnvironment(EnvironmentName.Development);
        });

Once I set that I got more details about my misfiring Blazor code.

A Blazor specific approach:

An alternative approach for turning on detailed errors can also be found in this answer, which includes this code:

services.AddServerSideBlazor().AddCircuitOptions(options => {  options.DetailedErrors = true; });

This approach can then be expanded to include a check for whether the code is being run in the development environment

services.AddServerSideBlazor().AddCircuitOptions(o =>
{
    //only add details when debugging
    o.DetailedErrors = _env.IsDevelopment();
});

as highlighted by @Eonasdan’s answer below