Resolving TagHelpers from an assembly that only has runtime TagHelpers creates an error at design time.

[NTaylorMullen]

If an assembly (Microsoft.AspNetCore.Mvc.Razor) only contains TagHelpers that have editor browsable never then we log an error in our binder syntax tree pass stating that no TagHelpers exist in the assembly.

[NTaylorMullen]

I temporarily worked around this issue to unblock tooling folks in this commit. We never used to validate that an assembly had TagHelpers in the old world so my temporary workaround might be an ok fix. However, the error was definitely intentional so it means there was a drive for it. Other fixes could be:

1. Have a property on descriptors, descriptor.EditorBrowsable, and then filter them out before returning any to the editor.
2. Leave the error but conditionally add Mvc.Razor tag helper bits based on if design time or not. This would result in the MvcRazorTemplateEngine signature changing to include a design time parameter.

Looking for opinions @rynowak / @pranavkm / @ajaybhargavb

[ajaybhargavb]

Have a property on descriptors, descriptor.EditorBrowsable, and then filter them out before returning any to the editor.

Will doing this make it so that we create descriptor only for this error check and the ones with EditorBrowable set to false will be pretty useless otherwise?

[NTaylorMullen]

Will doing this make it so that we create descriptor only for this error check and the ones with EditorBrowable set to false will be pretty useless otherwise?

yar

[rynowak]

Close? I like the solution we ended up with.