AddCheck<MySqlHealthCheck> throws InvalidOperationException for missing MySqlHealthCheckOptions

[bgrainger]

What happened:

I added a MySQL health check to a simple ASP.NET 8.0 Web API project. When accessing the health check URL I got the following exception:

InvalidOperationException: Unable to resolve service for type 'HealthChecks.MySql.MySqlHealthCheckOptions' while attempting to activate 'HealthChecks.MySql.MySqlHealthCheck'.
Microsoft.Extensions.DependencyInjection.ActivatorUtilities+ConstructorMatcher.CreateInstance(IServiceProvider provider)
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, object[] parameters)
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance<T>(IServiceProvider provider)
Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService.RunCheckAsync(HealthCheckRegistration registration, CancellationToken cancellationToken)
Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService.RunCheckAsync(HealthCheckRegistration registration, CancellationToken cancellationToken)
Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService.CheckHealthAsync(Func<HealthCheckRegistration, bool> predicate, CancellationToken cancellationToken)
Microsoft.AspNetCore.Diagnostics.HealthChecks.HealthCheckMiddleware.InvokeAsync(HttpContext httpContext)
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

What you expected to happen:

Expected that URL would return Healthy.

How to reproduce it (as minimally and precisely as possible):

Source code sample:

services.AddMySqlDataSource(builder.Configuration.GetConnectionString("mysql"));

services.AddHealthChecks()
	.AddCheck<MySqlHealthCheck>("MySQL");

// Need to add this line to make it work:
// services.AddSingleton(x => new MySqlHealthCheckOptions(x.GetRequiredService<MySqlDataSource>()));

Anything else we need to know?:

This was probably a regression introduced in #2096; I'll take a look at the code.

Environment:

• .NET Core version: 8.0
• Healthchecks version: 8.0
• Operative system: Windows 10
• Others:

[bgrainger]

It works out-of-the-box when using the API recommended in the documentation:

services.AddHealthChecks()
    .AddMySql();

[bgrainger]

This is a side-effect of the new API design suggested in #2113 (comment).

Following that change, DbHealthCheck no longer has a default constructor and can't be added with .AddCheck<DbHealthCheck>(). Instead, one has to use a new helper extension method, .AddDbHealthCheck().

This is probably best reclassified as a documentation bug: the new extension methods should always be used to add a database health check. (This could affect users upgrading from a previous version, but it is included in a package with a major version number change.)