We should be respecting $(ProjectAssetsFile)

[davkean]

We find the assets files ourselves in the ProjectLockFileWatcher. We shouldn't be doing that, we should respecting $(ProjectAssetsFile).
See: NuGet/Home#4463 (comment)

[nguerrera]

Something just occurred to me. @dsplaisted made changes so that SDK will not default ProjectAssetsFile and instead use what restore writes to generated temp props. Would this create a chicken-and-egg problem for initiating the watch when restore hasn't been done yet?

[davkean]

@nguerrera Yes, this is a chicken and egg. If we can't find $(ProjectAssetsFile) we can't tell CPS that it needs to reevaluate. We were also planning to move to a model where CPS itself monitored the file based on https://github.com/dotnet/project-system/blob/master/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/DesignTimeTargets/Microsoft.Managed.DesignTime.targets#L281 but sounds like this would also be broken by that.

[nguerrera]

:(

[dsplaisted]

I don't know how feasible this is, but I think the "right" thing to do would be to monitor the MSBuildProjectExtensionsPath. NuGet restore will drop .props and .targets which should be imported there, as well as the assets.json file. So when the new .props and .targets show up there the project should be re-evaluated. The .props file will then set the ProjectAssetsFile property, and you can then additionally watch for changes in that file if it's necessary.

[davkean]

We already monitor the props/targets when we reevaluate and they appear, also wouldn't play nicely with shared intermediates.

Was this change to remove logic from SDK? If so, can we add it back to NuGet targets?

[dsplaisted]

@davkean To clarify, will CPS detect when new .props / .targets files show up in the MSBuildProjectExtensionsPath, or will it only detect if files that were part of the evaluation initially are updated?

[davkean]

• Assets file changed
• Reevaluate
• New props/targets are picked up

We don't monitor for props/targets existence under they appear in evaluation - there's thousand of locations they could appear.