.NET 6 Fix .NET MAUI Blazor Scoped CSS Hot Reload

[TanayParikh]

Fixes: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1589099

Description

Scoped CSS Hot Reload doesn't work for .NET 6.0 MAUI Blazor apps, this is part one of a two part fix which resolves this issue in .NET 6.

Original Issue: #26762
VSTS issue requesting backport: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1589099

Backports:

• [Blazor] Update the base path to use IntermediateOutputPath #26765
• [Blazor] Allow customizing the static web assets base manifest paths if defined by the environment #27102

Will also need: dotnet/maui#9348 -> dotnet/maui#9393

Customer Impact

Hot reload of scoped CSS fails for .NET 6.0 MAUI Blazor applications without this (and the complementary dotnet/maui) change.

Regression?

• Yes
• No

Computation of these values were moved to a target resulting in this regression.

Risk

• High
• Medium
• Low

Low risk, we've already made these changes in main/net7.

Verification

• Manual (required)
• Automated

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[TanayParikh]

Companion PR: dotnet/maui#9393

[TanayParikh]

@dougbu @wtgodbe do you happen to know if we're okay to merge, or must this go through tactics?

[wtgodbe]

Seems fine as a tell-mode PR to me.

[TanayParikh]

Seems fine as a tell-mode PR to me.

Sounds good, thanks! cc/ @marcpopMSFT in case you have any concerns :)

(Not seeing a tell-mode label so not annotating anything).

[marcpopMSFT]

Tell mode is generally used for infrastructure changes and test changes. Isn't this a change to the customer-facing razor targets?

[TanayParikh]

Tell mode is generally used for infrastructure changes and test changes. Isn't this a change to the customer-facing razor targets?

Yes these targets will have direct customer impact. This is required to help resolve https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1589099 which is causing hot reload failures in .NET 6. We'll be merging this in conjunction with dotnet/maui#9393.

@marcpopMSFT what would you suggest the appropriate process be in that case? Ask mode (ask you?) or would it be through tactics + servicing template?

[marcpopMSFT]

Since there is direct customer impact, I would mark servicing-consider, update the description with the template (look for other servicing-approved bugs for the template), and send mail to tactics.

[marcpopMSFT]

@TanayParikh @mkArtakMSFT @javiercn pinged offline as well but if this is needed for servicing, it should be merged today.