Expose building blocks for external service discovery implementations

[bart-vmware]

Closes #dotnet/aspire#4224.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR exposes building blocks for external service discovery implementations by making previously internal APIs public. The changes enable external developers to implement custom service discovery providers while maintaining consistency with internal patterns.

Key changes:

• Made UriEndPoint class public with proper constructor and null validation
• Exposed ApplyAllowedSchemes as a public instance method on ServiceDiscoveryOptions
• Added ServiceEndpoint.TryParse static method to provide a standard way to parse endpoint strings

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
ServiceDiscoveryOptions.cs	Changed ApplyAllowedSchemes from internal static to public instance method with XML documentation
ConfigurationServiceEndpointProvider.cs	Updated to use new public ApplyAllowedSchemes method and consolidated endpoint parsing logic
UriEndPoint.cs	Changed from internal sealed to public class with public constructor and null validation
ServiceEndpoint.cs	Added public TryParse method to centralize endpoint string parsing logic

[Copilot]

The pragma warning disable for CS8602 is unnecessary here. The preceding check !string.IsNullOrWhiteSpace(value) on line 66 ensures that value is not null at this point, so the null-forgiving operator or null check is not needed. Remove the pragma directives.

Suggested change

	#pragma warning disable CS8602
	if (value.IndexOf("://", StringComparison.Ordinal) < 0 && Uri.TryCreate($"fakescheme://{value}", default, out var uri))
	#pragma warning restore CS8602
	if (value.IndexOf("://", StringComparison.Ordinal) < 0 && Uri.TryCreate($"fakescheme://{value}", default, out var uri))

[bart-vmware]

This isn't true. The build fails without it. That's because string.IsNullOrWhiteSpace is not annotated for nullability in netstandard and netfx.

[Copilot]

This code performs a type check and potentially creates a new array on every instantiation. Since ApplyAllowedSchemes now returns IReadOnlyList<string> and can return different concrete types (ReadOnlyCollection<string> or List<T>.AsReadOnly()), consider storing allowedSchemes directly as IReadOnlyList<string> if _schemes field type can be changed, or call .ToArray() unconditionally to avoid the type check overhead.

Suggested change

	_schemes = allowedSchemes as string[] ?? allowedSchemes.ToArray();
	_schemes = allowedSchemes.ToArray();

[bart-vmware]

The updated code employs the same optimization to avoid allocating when the runtime type is already an array. The logic has just moved.

[bart-vmware]

@ReubenBond, can you please review this PR?

[bart-vmware]

@ReubenBond Thanks for the review and approval.
@davidfowl I've rebased on the latest main after approval. Do we need another pair of eyes, or is this ready to merge now?