azd init fails when External Service Parameter has no default value and configuration key is missing

[eerhardt]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When running azd init against an Aspire distributed application that includes a Parameter with no default value, the initialization fails if the configuration key for that parameter is missing. The error indicates a MissingParameterValueException is thrown and the distributed application cannot be published.

Sample code:

var builder = DistributedApplication.CreateBuilder(args);

var externalServiceUrl = builder.AddParameter("externalServiceUrl");

var externalService = builder.AddExternalService("external-service", externalServiceUrl);

builder.AddProject<Projects.ParameterTest_Web>("webfrontend")
    .WithEnvironment("EXTERNAL_SERVICE", externalService);

builder.Build().Run();

Command:
azd init

Expected Behavior

I expected azd init to succeed or prompt for the missing parameter, rather than fail with a runtime exception. Ideally, the tool should either require the configuration key to be present or guide the user to supply a value, instead of crashing.

Steps To Reproduce

1. Create an Aspire distributed app with a parameter with no default value, as shown above.
2. Run azd init in the app directory.
3. Observe the failure and exception output.

Exceptions (if any)

Aspire.Hosting.MissingParameterValueException: Parameter resource could not be used because configuration key 'Parameters:externalServiceUrl' is missing and the Parameter has no default value.

Full stack trace:

Aspire.Hosting.MissingParameterValueException: Parameter resource could not be used because configuration key 'Parameters:externalServiceUrl' is missing and the Parameter has no default value.
   at Aspire.Hosting.ParameterResourceBuilderExtensions.GetParameterValue(ConfigurationManager configuration, String name, ParameterDefault parameterDefault, String configurationKey) in /_/src/Aspire.Hosting/ParameterResourceBuilderExtensions.cs:line 207
   at Aspire.Hosting.ParameterResourceBuilderExtensions.<>c__DisplayClass0_0.<AddParameter>b__0(ParameterDefault parameterDefault) in /_/src/Aspire.Hosting/ParameterResourceBuilderExtensions.cs:line 32
   at Aspire.Hosting.ApplicationModel.ParameterResource.<.ctor>b__3_0() in /_/src/Aspire.Hosting/ApplicationModel/ParameterResource.cs:line 27
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at Aspire.Hosting.ApplicationModel.ParameterResource.get_ValueInternal() in /_/src/Aspire.Hosting/ApplicationModel/ParameterResource.cs:line 36
   at Aspire.Hosting.ApplicationModel.ParameterResource.GetValueAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting/ApplicationModel/ParameterResource.cs:line 87
   at Aspire.Hosting.ResourceBuilderExtensions.<>c__DisplayClass8_0`1.<<WithEnvironment>b__0>d.MoveNext() in /_/src/Aspire.Hosting/ResourceBuilderExtensions.cs:line 182
--- End of stack trace from previous location ---
   at Aspire.Hosting.ApplicationModel.ResourceExtensions.ProcessEnvironmentVariableValuesAsync(IResource resource, DistributedApplicationExecutionContext executionContext, Action`4 processValue, ILogger logger, String containerHostName, CancellationToken cancellationToken) in /_/src/Aspire.Hosting/ApplicationModel/ResourceExtensions.cs:line 352
   at Aspire.Hosting.Publishing.ManifestPublishingContext.WriteEnvironmentVariablesAsync(IResource resource) in /_/src/Aspire.Hosting/Publishing/ManifestPublishingContext.cs:line 490
   at Aspire.Hosting.Publishing.ManifestPublishingContext.WriteProjectAsync(ProjectResource project) in /_/src/Aspire.Hosting/Publishing/ManifestPublishingContext.cs:line 177
   at Aspire.Hosting.Publishing.ManifestPublishingContext.<>c__DisplayClass20_0.<<WriteResourceAsync>g__WriteResourceObjectAsync|1>d`1.MoveNext() in /_/src/Aspire.Hosting/Publishing/ManifestPublishingContext.cs:line 129
--- End of stack trace from previous location ---
   at Aspire.Hosting.Publishing.ManifestPublishingContext.WriteResourceAsync(IResource resource) in /_/src/Aspire.Hosting/Publishing/ManifestPublishingContext.cs:line 107
   at Aspire.Hosting.Publishing.ManifestPublishingContext.WriteModel(DistributedApplicationModel model, CancellationToken cancellationToken) in /_/src/Aspire.Hosting/Publishing/ManifestPublishingContext.cs:line 79
   at Aspire.Hosting.Publishing.ManifestPublisher.WriteManifestAsync(DistributedApplicationModel model, Utf8JsonWriter jsonWriter, CancellationToken cancellationToken) in /_/src/Aspire.Hosting/Publishing/ManifestPublisher.cs:line 67
   at Aspire.Hosting.Publishing.ManifestPublisher.PublishInternalAsync(DistributedApplicationModel model, CancellationToken cancellationToken) in /_/src/Aspire.Hosting/Publishing/ManifestPublisher.cs:line 55
   at Aspire.Hosting.Publishing.ManifestPublisher.PublishAsync(DistributedApplicationModel model, CancellationToken cancellationToken) in /_/src/Aspire.Hosting/Publishing/ManifestPublisher.cs:line 23
   at Aspire.Hosting.DistributedApplicationRunner.ExecuteAsync(CancellationToken stoppingToken) in /_/src/Aspire.Hosting/DistributedApplicationRunner.cs:line 41
fail: Microsoft.Extensions.Hosting.Internal.Host[11]
      Hosting failed to start

.NET Version info

No response

Anything else?

No response

[eerhardt]

cc @DamianEdwards

[DamianEdwards]

So this is an issue with parameters with no value with azd, not external services specifically, right?

[eerhardt]

So this is an issue with parameters with no value with azd, not external services specifically, right?

No. It is specific to external services AFAICT. If I remove it and just pass the Parameter into the Environment it works just fine.

Works

var builder = DistributedApplication.CreateBuilder(args);

var externalServiceUrl = builder.AddParameter("externalServiceUrl");

//var externalService = builder.AddExternalService("external-service", externalServiceUrl);

builder.AddProject<Projects.ParameterTest_Web>("webfrontend")
    .WithEnvironment("EXTERNAL_SERVICE", externalServiceUrl);

builder.Build().Run();

[eerhardt]

BTW - This was found by running the generate-manifests launch profile on our playground app:

aspire/playground/ExternalServices/ExternalServices.AppHost/AppHost.cs

Lines 9 to 20 in ee7ef1d

	var externalServiceUrl = builder.AddParameter("external-service-url")
	.WithDescription("The URL of the external service.")
	.WithCustomInput(p => new()
	{
	InputType = InputType.Text,
	Value = "https://example.com",
	Label = p.Name,
	Placeholder = $"Enter value for {p.Name}",
	Description = p.Description
	});
	#pragma warning restore ASPIREINTERACTION001
	var externalService = builder.AddExternalService("external-service", externalServiceUrl);

[DamianEdwards]

Odd. Can you compare and share the manifests for each?

[eerhardt]

Can you compare and share the manifests for each?

The manifest generation fails in the middle with the above exception. Look how it just cuts off mid-JSON:

aspire/playground/ExternalServices/ExternalServices.AppHost/aspire-manifest.json

Lines 33 to 44 in ee7ef1d

	"bindings": {
	"http": {
	"scheme": "http",
	"protocol": "tcp",
	"transport": "http",
	"targetPort": 5000
	}
	}
	},
	"frontend": {
	"type": "project.v0",
	"path": "../WebFrontEnd/WebFrontEnd.csproj"

that's the EOF

[eerhardt]

I think the bug is at line 182:

aspire/src/Aspire.Hosting/ResourceBuilderExtensions.cs

Lines 166 to 188 in 9ccd681

	public static IResourceBuilder<T> WithEnvironment<T>(this IResourceBuilder<T> builder, string name, IResourceBuilder<ExternalServiceResource> externalService)
	where T : IResourceWithEnvironment
	{
	ArgumentNullException.ThrowIfNull(builder);
	ArgumentNullException.ThrowIfNull(externalService);
	builder.WithReferenceRelationship(externalService.Resource);
	if (externalService.Resource.Uri is not null)
	{
	builder.WithEnvironment(name, externalService.Resource.Uri.ToString());
	}
	else if (externalService.Resource.UrlParameter is not null)
	{
	builder.WithEnvironment(async context =>
	{
	var url = await externalService.Resource.UrlParameter.GetValueAsync(context.CancellationToken).ConfigureAwait(false);
	// In publish mode we can't validate the parameter value so we'll just use it without validating.
	if (!context.ExecutionContext.IsPublishMode && !ExternalServiceResource.UrlIsValidForExternalService(url, out var _, out var message))
	{
	throw new DistributedApplicationException($"The URL parameter '{externalService.Resource.UrlParameter.Name}' for the external service '{externalService.Resource.Name}' is invalid: {message}");
	}

We can't call GetValueAsync when in "Publish Mode" (i.e. manifest generation).

it is interesting that we check for publish after this though.

[eerhardt]

Yep that seemed to fix it:

            builder.WithEnvironment(async context =>
            {
                if (!context.ExecutionContext.IsPublishMode)
                {
                    var url = await externalService.Resource.UrlParameter.GetValueAsync(context.CancellationToken).ConfigureAwait(false);

                    // In publish mode we can't validate the parameter value so we'll just use it without validating.
                    if (!ExternalServiceResource.UrlIsValidForExternalService(url, out var _, out var message))
                    {
                        throw new DistributedApplicationException($"The URL parameter '{externalService.Resource.UrlParameter.Name}' for the external service '{externalService.Resource.Name}' is invalid: {message}");
                    }
                }

let's the manifest go through. I'll submit a PR

[davidfowl]

9.4.1?