Improve KnownFrameworkReference workarounds in templatetests.props.in

[wtgodbe]

462acbe#diff-a0bc203ab59b1a2f006b56858a20684b removed the TargetFramework metadata from the KnownFrameworkReference workarounds in templatetests.props.in. We need these workarounds in order to reference the desired versions of Microsoft.Netcore.App (the one we depend on in versions.props, rather than the one the SDK depends on). However, the current workaround modifies the metadata for all KnownFrameworkReference items for Microsoft.Netcore.App/Microsoft.AspNetcore.App, rather than just the ones that match the TFM of the desired reference version. This is because, during the build of the template test projects, conditions on Item metadata give the following error:

error MSB4191: The reference to custom metadata "TargetFramework" at position 1 is not allowed in this condition "'%(TargetFramework)' == 'netcoreapp3.1'".

This happens for both of the following conditions:

Condition="'%(TargetFramework)' == '${DefaultNetCoreTargetFramework}'"

Condition="'%(KnownFrameworkReference.TargetFramework)' == '${DefaultNetCoreTargetFramework}'"

We should investigate why this error occurs only in the template tests, and what we can do to work around it so that we can apply this condition to the update. It's worth noting that the same workaround appears in release/3.1, so we should decide if it's worth fixing there as well.

CC @dougbu @JunTaoLuo @Pilchie

[dougbu]

@rainersigwald any suggestions on avoiding the error @wtgodbe describes above?

[rainersigwald]

You can't do that kind of metadata expansion in a condition outside of a target. Can you move the filtering operation to a target?

[dougbu]

@wtgodbe anything new for this issue?

[wtgodbe]

Not yet, we can keep this in backlog for now

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[dougbu]

Taking this because it's addressed in #27473

[dougbu]

To clarify: The templates used in the GenerateFiles project introduced in #26788 avoided updates to all @(KnownFrameworkReference) items using WithMetadataValue(...) item function calls, avoiding unsupported Conditions. #27473 finishes the job because it uses the GenerateFiles output for the project template test assets.

[dougbu]

5fd1db2