Update attribute can only appear in static items

[cdmihai]

Resolves #1618

[nguerrera]

Can we take this to ship room? I think we need this in RTW

[rainersigwald]

@nguerrera I don't think it meets the bar now, but we can bring it up in standup today.

[nguerrera]

Isn't it a now or never language change? Does bar sill have that. This feels like silent bad code gen equivalent for msbuild. It would be breaking to make it work as I expect if not an error now.

[nguerrera]

Also breaking to go from non error to error

[cdmihai]

Ideally, the correct thing to do is to error now for RTW, to increase the user friendliness and debug-ability. And then, post RTW, allow Update for targets too. Along with everything else in #1124.

Prior to dev15, msbuild did have an Update only for dynamic items (items in targets). It works like this: #955. This is the code path that hits if you put an Update inside targets. The Update gets ignored and the old behaviour kicks in, which is equivalent to <Compile Update="@(Compile)">.

More details here.

[nguerrera]

Agree on error now support later.

I'm aware of the existing target mechanism, but it is cumbersome. Could you guys look at my use case in the bug comment and let me know how to express it with just a condition?

[rainersigwald]

I was just surprised this didn't happen. Did we decide not to make this an error? Did we just miss shiproom? I don't remember at all :(

[cdmihai]

Same here, no idea what happened. My vague memory is ship-room miss-alignment. Should we bring the error back? Or just wait until we port Update to targets?