Add .cshtml.css styles in default project templates

[mkArtakMSFT]

This will help with adoption of CSS Isolation.

[ghost]

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[captainsafia]

I took a stab at doing this when I was fixing an scoped CSS issue in #31257 but it induced a ton of flakiness in the build.

In particular, our template tests do a validation where they check to see if the static assets requested by an app are received. For some reason, the generated CSS file from the scoped CSS throws a 404 sometimes.

Expected /AspNet._1rfblykoltv.styles.css to have status 'OK' but it was 'NotFound'.
Expected: True
Actual:   False

at Templates.Test.Helpers.AspNetProcess.AssertStatusCode(String requestUrl, HttpStatusCode statusCode, String acceptContentType) in /_/src/ProjectTemplates/Shared/AspNetProcess.cs:line 256
   at Templates.Test.Helpers.AspNetProcess.ContainsLinks(Page page) in /_/src/ProjectTemplates/Shared/AspNetProcess.cs:line 138
   at Templates.Test.Helpers.AspNetProcess.AssertPagesOk(IEnumerable`1 pages) in /_/src/ProjectTemplates/Shared/AspNetProcess.cs:line 117
   at Templates.Test.MvcTemplateTest.MvcTemplateCore(String languageOverride) in /_/src/ProjectTemplates/test/MvcTemplateTest.cs:line 108
   at Templates.Test.MvcTemplateTest.MvcTemplate_NoAuthCSharp() in /_/src/ProjectTemplates/test/MvcTemplateTest.cs:line 44
--- End of stack trace from previous location ---

https://dev.azure.com/dnceng/public/_build/results?buildId=1064596&view=ms.vss-test-web.build-test-results-tab&runId=32774366&resultId=123661

If we pursue this work, we'll probably need to get to the bottom of this.

As a sidenote: while working on the scoped CSS issue I was able to verify that it generally works as expected.

[javiercn]

@captainsafia I suspect this is because the check /AspNet._1rfblykoltv.styles.css might not match the actual file scoped CSS generates. I think it is fine to skip this file if you want on the test to avoid the flakyness.

[captainsafia]

Ah I see. I guess we'll have to add a way to exempt that particular file here:

aspnetcore/src/ProjectTemplates/Shared/AspNetProcess.cs

Line 135 in a67c2cf

foreach (IHtmlLinkElement styleSheet in html.GetElementsByTagName("link"))

[ghost]

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. Because it's not immediately obvious that this is a bug in our framework, we would like to keep this around to collect more feedback, which can later help us determine the impact of it. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[mkArtakMSFT]

@captainsafia I assume this is now done, isn't it?

[captainsafia]

Yep! Not sure why it didn't close when I merged the PR.