WaitForCompletion seems incompatible with watch

[willdean]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

TL;DR: WaitForCompletion does not work when using dotnet watch or aspire run --watch

We are playing with Aspirifying a .NET 8 Blazor (server) app which uses EF Core with Postgresql. We're using Aspire 9.3 and generally use the 8.0 SDK but have also tested with the 9.0 SDK before opening this issue.

• Following the guidelines we created a separate 'Migrations' project to run the EF migrations (and seeding) at startup.
• In order to make sure the migrations complete before the app tries to start, we had to add WaitForCompletion to the app service. This works OK when using aspire run
• Because this is Blazor server app, we need to use dotnet watch (or aspire run --watch) for any kind of realistic development loop performance. Unfortunately when running AppHost under either of those CLI-based watch commands, the Migrations service does not actually complete. This means that the web app never starts, because of its WaitForCompletion
• Manually clicking 'stop' on the Migrations service in the dashboard does release the web app to start.

I have not tried any kind of IDE-based hot-reload.

There was a previous mention of this here, but it was an addition to an issue which is now closed: #6695 (comment)

I doubt "Blazor + EF Migrations" really qualifies as a corner-case so I am probably missing something here, but if I'm not, could we we have one of these:

• Some way to manually mark a service as not-for-hot-reload (clearly it's just useless busywork on a one-shot app anyway)
• Aspire could detect the WaitForCompletion and mark the relevant service as not-for-hot-reload
• The WaitForCompletion logic could understand the 'watch' quirks a little better and work around them

I am currently running on a Mac but can test on Windows if that might be relevant.

Expected Behavior

I expect that using watch/hot reload should be compatible with using WaitForCompletion

Steps To Reproduce

Minimal repro:

https://github.com/willdean/aspire-watch-start-issue

Exceptions (if any)

No response

.NET Version info

.NET SDK:
Version: 9.0.203
Commit: dc7acfa194
Workload version: 9.0.200-manifests.87b8cca8
MSBuild version: 17.13.20+a4ef1e90f

Runtime Environment:
OS Name: Mac OS X
OS Version: 15.5
OS Platform: Darwin
RID: osx-arm64
Base Path: /usr/local/share/dotnet/sdk/9.0.203/

.NET workloads installed:
[aspire]
Installation Source: SDK 9.0.200
Manifest Version: 8.2.2/8.0.100
Manifest Path: /usr/local/share/dotnet/sdk-manifests/8.0.100/microsoft.net.sdk.aspire/8.2.2/WorkloadManifest.json
Install Type: FileBased

Configured to use loose manifests when installing new manifests.

Host:
Version: 9.0.4
Architecture: arm64
Commit: f57e6dc747

.NET SDKs installed:
6.0.418 [/usr/local/share/dotnet/sdk]
7.0.404 [/usr/local/share/dotnet/sdk]
8.0.100 [/usr/local/share/dotnet/sdk]
8.0.404 [/usr/local/share/dotnet/sdk]
8.0.407 [/usr/local/share/dotnet/sdk]
9.0.203 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.26 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.14 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.11 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.14 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.4 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.26 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.14 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.11 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.14 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.4 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
None

Environment variables:
Not set

global.json file:
Not found

Anything else?

No response

[Dona278]

We experienced the same issue with all console app which works as "development setup". From net8 to net9 with the command dotnet watch the project remaing in Running even with a forced application exit.

[willdean]

I know that 'watch' is supposed to be better in 10, but this is still happening in Preview 5.

[WillEhrendreich]

Is there any workaround for this other than hitting the Stop button every time?

Ideally, I'd love for the Aspire app to be running normally, but let another sub project be watched, so that the apphost doesn't have to be rebuilt every time, but any changes I make to the real business logic or test code gets to be refreshed and re-run.

Good luck on this, @tmat.

[willdean]

Is there any workaround for this other than hitting the Stop button every time?

I stumbled across this today, which implies that it sbould be possible for Aspire to start apps in ether "IDE" mode (which includes dotnet watch) or in normal (i.e. "just run it") mode. I don't know if this document is still relevant or this functionality is exposed, but if it was then it seems like a good solution to this problem would be to have a way to mark applications which are expected to run to completion as avoiding the "IDE mode" altogether. There's simply no point hooking-up the hot-reload mechanism to an app which is going to have finished and exited within a few seconds.

Edit: Having looked at DcpExecutor.cs, I don't think this is currently possible - roughly speaking, all projects are started in "IDE" mode and only plain executables in "Process" mode.