Add hidden --cli-otlp-endpoint switch.

src/Aspire.Cli/Commands/RootCommand.cs

@@ -27,6 +27,25 @@ public RootCommand(NewCommand newCommand, RunCommand runCommand, AddCommand addC
         waitForDebuggerOption.Recursive = true;
         waitForDebuggerOption.DefaultValueFactory = (result) => false;
 
+        var otelOption = new Option<string>("--cli-otlp-endpoint");
+        otelOption.Description = "Send telemetry to the OpenTelemetry collector";
+        otelOption.Validators.Add((result) => {
+                var otelUrl = result.GetValueOrDefault<string>();
+
+                if (Uri.TryCreate(otelUrl, UriKind.Absolute, out var otelUri) && (otelUri.Scheme == Uri.UriSchemeHttp || otelUri.Scheme == Uri.UriSchemeHttps))
+                {
+                    // If we have a valid URL then we can just return.
+                    return;
+                }
+                else
+                {
+                    result.AddError("The OpenTelemetry URL must be an absolute URI with either HTTP or HTTPS scheme.");
+                }
+        });
+        otelOption.Recursive = true;
+        otelOption.Hidden = true; // Hiding for now since this could be confusing about what it does.
+        Options.Add(otelOption);
+
         #if DEBUG
         waitForDebuggerOption.Validators.Add((result) => {
 

src/Aspire.Cli/Program.cs

@@ -12,6 +12,7 @@
 using OpenTelemetry;
 using OpenTelemetry.Resources;
 using OpenTelemetry.Trace;
+using Spectre.Console;
 using RootCommand = Aspire.Cli.Commands.RootCommand;
 
 namespace Aspire.Cli;
@@ -49,12 +50,22 @@ private static IHost BuildApplication(string[] args)
                 tracing.SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("aspire-cli"));
             });
 
-        if (builder.Configuration["OTEL_EXPORTER_OTLP_ENDPOINT"] is {})
+        // NOTE: Actual arg validation will take place elsewhere, this is just
+        //       a quick check to make sure that DI is configured correctly.
+        if (args.IndexOf("--cli-otlp-endpoint") is var otelArgIndex && otelArgIndex != -1)
         {
-            // NOTE: If we always enable the OTEL exporter it dramatically
-            //       impacts the CLI in terms of exiting quickly because it
-            //       has to finish sending telemetry.
-            otelBuilder.UseOtlpExporter();
+            // If we have an --cli-otlp-endpoint switch then we need to check that we
+            // have at least enough args to have a base URL.
+            if (args.Length == otelArgIndex + 2)
+            {
+                var baseUrl = args[otelArgIndex + 1];
+
+                // If we have enough arguments we need to make sure its a valid URL.
+                if (Uri.TryCreate(baseUrl, UriKind.Absolute, out var baseUri) && (baseUri.Scheme == Uri.UriSchemeHttp || baseUri.Scheme == Uri.UriSchemeHttps))
+                {
+                    otelBuilder.UseOtlpExporter(OpenTelemetry.Exporter.OtlpExportProtocol.Grpc, baseUri);
+                }
+            }
         }
 
         var debugMode = args?.Any(a => a == "--debug" || a == "-d") ?? false;