[WASM regression] Crazy long debug build times

[mikernet]

Current behavior

WASM debug builds (or starting projects with/without debugging in VS) take a crazy long time for new projects, on the order of ~3 minutes on every build/launch for a blank new project. CPU usage is effectively 0 during the vast majority of this time. Monitoring the current msbuild task when doing dotnet build does not seem to indicate any one particular culprit - many of the WASM specific build tasks (generating JSON, generating assets, etc) take a very long time:

20250328-0616-31.7005845.mp4

This does not happen on older projects that started at version 5.2.x where I progressively incremented Uno version in global.json to latest - I can build and launch large applications in ~10 seconds. Downgrading Uno.Sdk version to 5.5.62 after creating a new project with the latest templates does not fix the issue.

Expected behavior

Should build quickly.

How to reproduce it (as minimally and precisely as possible)

See attached project, which was created using latest Uno templates with only had a couple minor changes: TestUno.zip. Do dotnet build or start with/without debugging in VS and notice it takes a few minutes to build.

Workaround

No response

Works on UWP/WinUI

Yes

Environment

Uno.UI / Uno.UI.WebAssembly / Uno.UI.Skia, Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia

NuGet package version(s)

5.6.51, 5.6.45

Affected platforms

WebAssembly

IDE

Visual Studio 2022

IDE version

VS 17.13.2, 17.13.5
Uno Platform VS Extension 5.6.42.66
Latest uno-check all good

Relevant plugins

No response

Anything else we need to know?

No response

[jeromelaban]

Thanks for the report. This project builds in between 30s (first run) and 3s (subsequent run).

Could you provide a binlog?