[Built-in analyzer] Item is updated inside a target

[ladipro]

Background

This issue tracks one of the BuildCheck analyzers we would like to ship in-box with MSBuild.

Goal

Implement an analyzer with the following rule: No item is attempted to be updated using the Update attribute inside a target.

Notes

While the Update attribute can be added to items inside a target, it is ignored and the transformation is applied to all items of the given type. Implementing this analyzer will likely require introducing TaskParameterMessageKind.UpdateItem to communicate the attempted operation to the analyzer.

[rainersigwald]

This is a mitigation for #2835.

this functionality is not supported inside targets and the engine silently does nothing

Nit: the problem isn't that the engine does nothing, it's that it ignores the Update attribute, applying the transformation to all items of that type instead of a filtered list.

[ladipro]

I have updated the description, thank you!

[sharwell]

Related to:

• No error for Item update in target #2835
• Log Item Updates in Targets #3538

If the engine instead was updated to honor the attribute, this analysis would not be needed. However, it sounds like that isn't an option.

[rainersigwald]

This is not related to #3538--that's about the update mechanism that has existed ~forever, rather than the Update attribute.

Indeed, honoring the attribute would be a breaking change 😢

[KirillOsenkov]

wish we could opt in to honoring the attribute somehow, and then gradually roll out the opt in over the years

[KirillOsenkov]

hopefully setting a property as an opt in mechanism could work

[KirillOsenkov]

I'm sure 100% of people when asked, do you want this semantics to be fixed at the risk of you having to update your build? would emphatically say yes

[rainersigwald]

I wish I believed that. I would expect a bunch of angry bugs.

[rainersigwald]

An opt-in property could work since it'd be set before any target executed . . . that's a GREAT idea.