[MTP Diagnostic Analysis] AddOpenTelemetryProvider defaults to a no-op despite documented default behavior

[Evangelink]

Summary

AddOpenTelemetryProvider() documents that null delegates use default tracing/metrics behavior, but the implementation just builds empty TracerProvider / MeterProvider instances. No Microsoft Testing Platform instrumentation or exporter is added unless the caller wires everything manually.

Evidence

• Q:\src\testfx\src\Platform\Microsoft.Testing.Extensions.OpenTelemetry\OpenTelemetryProviderExtensions.cs:20-29
  • If no delegates are supplied, default OpenTelemetry settings are used.
  • public static void AddOpenTelemetryProvider(..., Action<TracerProviderBuilder>? withTracing = null, Action<MeterProviderBuilder>? withMetrics = null)
• Q:\src\testfx\src\Platform\Microsoft.Testing.Extensions.OpenTelemetry\OpenTelemetryProvider.cs:19-25
  • TracerProviderBuilder tracerProviderBuilder = Sdk.CreateTracerProviderBuilder();
  • withTracing?.Invoke(tracerProviderBuilder);
  • _tracerProvider = tracerProviderBuilder.Build();
  • MeterProviderBuilder meterProviderBuilder = Sdk.CreateMeterProviderBuilder();
  • withMetrics?.Invoke(meterProviderBuilder);
  • _meterProvider = meterProviderBuilder.Build();
• Q:\src\testfx\src\Platform\Microsoft.Testing.Extensions.OpenTelemetry\OpenTelemetryProviderExtensions.cs:45-59
  • AddTestingPlatformInstrumentation(...) => builder.AddSource(OpenTelemetryPlatformService.ActivitySourceName);
  • AddTestingPlatformInstrumentation(...) => builder.AddMeter(OpenTelemetryPlatformService.MeterName);
• Q:\src\testfx\samples\public\MTPOTel\Program.cs:31-42
  • sample has to call tracing.AddTestingPlatformInstrumentation();
  • sample has to call metrics.AddTestingPlatformInstrumentation();
  • sample has to add exporters explicitly.

Why this is a real issue

builder.AddOpenTelemetryProvider(); looks valid from the API and XML docs, but it produces no test traces or metrics. The package README also says the extension "instruments test execution with OpenTelemetry-compatible traces and metrics", which is not true for the zero-configuration path.

Suggested resolution

Either:

1. register Microsoft Testing Platform instrumentation by default (and document that exporters are still caller-configured), or
2. fail fast / warn when neither delegate configures instrumentation/exporters, and update the XML docs/README so the API contract matches reality.

Related issues

• None found