feat(dapr): add IValueProvider support for component metadata configuration

[gabynevada]

Summary

• Adds support for using IValueProvider (including EndpointReference) in Dapr component metadata configuration
• Enables dynamic endpoint resolution for Dapr components at runtime
• Maintains backward compatibility with existing string and ParameterResource overloads

Changes

• Added new WithMetadata overload accepting IValueProvider for flexible metadata configuration
• Implemented deferred value resolution through environment variables and secretKeyRef mechanism
• Added DaprComponentValueProviderAnnotation to track value providers requiring resolution
• Updated lifecycle hook to resolve and inject endpoint values at runtime
• Enhanced DaprComponentSchema with async value resolution capabilities

Test Plan

• Added unit tests for EndpointReference metadata configuration
• Added tests for value provider resolution in component schema
• Added tests for multiple endpoint references
• Updated example to demonstrate Redis endpoint usage with the new feature
• Verified backward compatibility with existing metadata configuration methods

Example Usage

var redis = builder.AddRedis("redis");

var redisHost= redis.Resource.PrimaryEndpoint.Property(EndpointProperty.Host);
var redisTargetPort = redis.Resource.PrimaryEndpoint.Property(EndpointProperty.TargetPort);

var pubsub = builder
  .AddDaprPubSub("pubsub")
  .WithMetadata(
    "redisHost",
    ReferenceExpression.Create(
      $"{redisHost}:{redisTargetPort}"
    )
  );

This allows Dapr components to dynamically reference Aspire resource endpoints that are only known at runtime.

Closes #604

[davidfowl]

Did you implement the waiting? To make this work, the resource needs a lifecycle, see https://github.com/dotnet/aspire/blob/main/docs/specs/appmodel.md#built-in-resources--lifecycle.

When you implement IResourceWithWaitSupport, at some point you have to raise https://github.com/dotnet/aspire/blob/364382724b4cd3590ec75010525ce36ef0b5e769/src/Aspire.Hosting/ConnectionStringBuilderExtensions.cs#L92

[gabynevada]

Implemented it, don't know if it's the correct approach but I followed the examples. Also implemented on the IDaprComponentResource as it seems it was missing support

[Copilot]

Pull Request Overview

This PR adds support for using IValueProvider (including EndpointReference) in Dapr component metadata configuration, enabling dynamic endpoint resolution at runtime while maintaining backward compatibility.

Key changes include:

• Added new WithMetadata overload accepting IValueProvider for flexible metadata configuration
• Implemented deferred value resolution through environment variables and secretKeyRef mechanism
• Enhanced lifecycle management with proper dependency tracking and state management for Dapr sidecars

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Shared/Dapr/Core/DaprMetadataResourceBuilderExtensions.cs	Added new WithMetadata overload for IValueProvider with environment variable generation and secretKeyRef configuration
src/Shared/Dapr/Core/DaprDistributedApplicationLifecycleHook.cs	Enhanced lifecycle hook with value provider resolution, dependency management, and async environment variable setup
src/Shared/Dapr/Core/DaprComponentValueProviderAnnotation.cs	New annotation class to track value providers requiring deferred resolution
src/Shared/Dapr/Core/DaprComponentSchema.cs	Added async value resolution capabilities and new metadata provider type
src/Shared/Dapr/Core/IDistributedApplicationComponentBuilderExtensions.cs	Enhanced sidecar lifecycle with dependency tracking, state management, and proper event publishing
src/Shared/Dapr/Core/IDaprSidecarResource.cs	Added IResourceWithWaitSupport interface for proper dependency management
src/Shared/Dapr/Core/DaprSidecarEvents.cs	New event class for Dapr sidecar availability notifications
src/Shared/Dapr/Core/DaprComponentMetadataAnnotation.cs	Updated annotation to support async configuration with cancellation tokens
tests/dapr-shared/ResourceBuilderExtensionsTests.cs	Added comprehensive tests for EndpointReference metadata configuration and value provider resolution
tests/CommunityToolkit.Aspire.Hosting.Dapr.Tests/WithDaprSidecarTests.cs	Added test verifying sidecar WaitFor functionality
examples/dapr/CommunityToolkit.Aspire.Hosting.Dapr.AppHost/Program.cs	Updated example to demonstrate Redis endpoint usage with the new IValueProvider feature

[Copilot]

The State property assignment should be moved to after the resource is created but before the configureSidecar call, as the configureSidecar callback might expect the resource to have an initial state set.

[Copilot]

The EnvironmentCallbackAnnotation constructor expects a synchronous delegate, but an async lambda is being passed. This could lead to fire-and-forget behavior where exceptions are swallowed. Consider using a synchronous approach or ensure proper exception handling.

Suggested change

	daprSidecar.Annotations.Add(new EnvironmentCallbackAnnotation(async context =>
	{
	foreach (var secret in secrets)
	{
	context.EnvironmentVariables.TryAdd(secret.Key, secret.Value);
	}
	// Add value provider references
	foreach (var (envVarName, valueProvider) in endpointEnvironmentVars)
	{
	var value = await valueProvider.GetValueAsync(context.CancellationToken);
	context.EnvironmentVariables.TryAdd(envVarName, value ?? string.Empty);
	}
	// Precompute all value provider results asynchronously
	var precomputedEnvVars = new Dictionary<string, string>();
	foreach (var secret in secrets)
	{
	precomputedEnvVars[secret.Key] = secret.Value;
	}
	foreach (var (envVarName, valueProvider) in endpointEnvironmentVars)
	{
	// Synchronously block here to get the value
	// (since we're already in an async method, this is safe)
	var value = valueProvider.GetValueAsync(cancellationToken).GetAwaiter().GetResult();
	precomputedEnvVars[envVarName] = value ?? string.Empty;
	}
	daprSidecar.Annotations.Add(new EnvironmentCallbackAnnotation(context =>
	{
	foreach (var kvp in precomputedEnvVars)
	{
	context.EnvironmentVariables.TryAdd(kvp.Key, kvp.Value);
	}

[Copilot]

This internal class lacks XML documentation comments. As it's a key component for value provider functionality, it should have proper documentation explaining its purpose and usage.

Suggested change

	/// <summary>
	/// Represents a Dapr component spec metadata item whose value is provided by an <see cref="IValueProvider"/> and can be resolved asynchronously.
	/// </summary>

[gabynevada]

Here's the example:

WaitForRecording.mov

[FullStackChef]

@gabynevada just checking the state of the PR - are you wanting this re-reviewed? is it ready to merge?

[gabynevada]

@FullStackChef was occupied on work so could not do the final changes. Pushed the final changes so that the dapr component resources have a lifecycle and thus other resources can wait for them to get to the running state.

Let me know if anything needs to be changed!