Made changes to how parameter.Value works

[davidfowl]

Description

This was found while dogfooding the latest build with async parameter resolution. We were using ParameterResource.Value is many places and as a result those places did not properly wait for values to be resolved before continuing, they just failed. Now ParameterResource.Value calls ParameterResource.GetValueAsync(...).GetAwaiter().GetResult(), which is not great, but is consistent. We need the sync and async versions to work exactly the same way to avoid inconsistent state.

There's a risk with introducing deadlocks with this change for people that were using .Value before. I'm working through tests now to make sure that does not happen in practice. 👍🏾 If the Value is accessed before the TCS is set then it will throw an exception like it did before.

• Value now blocks (sync over async) waiting for value resolution if WaitForValueTcs is set.
• Made GetValueAsync on ParameterResource public.
• Changed most code outside of tests to use GetValueAsync instead of Value

Fixes #10352

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
• Did you add public API?
  • Yes
• Does the change make any security assumptions or guarantees?
  • No
• Does the change require an update in our Aspire docs?
  • No

[Copilot]

Pull Request Overview

This PR ensures that parameter values are resolved consistently by making ParameterResource.Value block on async resolution, exposing GetValueAsync, and updating callers to use the async API.

• ParameterResource.Value now synchronously awaits the async resolution path
• GetValueAsync is made public and most callers switch from .Value to .GetValueAsync(...)
• Call sites in various builder extensions are updated to await parameter values

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Aspire.Hosting/ResourceBuilderExtensions.cs	Await URL parameter resolution in WithEnvironment
src/Aspire.Hosting/Orchestrator/ParameterProcessor.cs	Switched from Value to ValueInternal in parameter processing
src/Aspire.Hosting/ExternalServiceBuilderExtensions.cs	Expose async URL retrieval and adjust initial state
src/Aspire.Hosting/ApplicationModel/ParameterResource.cs	Made GetValueAsync public and unified Value implementation
src/Aspire.Hosting.Redis/RedisBuilderExtensions.cs	Use async resolution for Redis password parameter
src/Aspire.Hosting.MySql/MySqlBuilderExtensions.cs	Await MySQL password parameter in PhpMyAdmin setup
src/Aspire.Hosting.Azure/Provisioning/Provisioners/BicepProvisioner.cs	Use GetValueAsync for parameter-based resource group names

Comments suppressed due to low confidence (1)

src/Aspire.Hosting/ApplicationModel/ParameterResource.cs:89

• New public API GetValueAsync was introduced but there are no unit tests for it. Consider adding tests to cover waiting on WaitForValueTcs and the fallback to ValueInternal.

    public async ValueTask<string?> GetValueAsync(CancellationToken cancellationToken)

[davidfowl]

/backport to release/9.4

[github-actions]

Started backporting to release/9.4: https://github.com/dotnet/aspire/actions/runs/16240431419