Duplicate build errors are not collapsed in the error list

[sharwell]

Version Used:

• Analysis scope set to Open Documents via Solution Explorer
• LSP pull diagnostics enabled

Steps to Reproduce:

1. Introduce a single build warning in a multi-targeted project
2. Build the project
3. Open the document with the build warning
4. Close the document with the build warning

Expected Behavior:

• After steps (2), (3), and (4), a single line appears in the error list showing the build warning

Actual Behavior:

• After step (2), one line appears in the error list for each target of the multi-targeted project. These lines are duplicates of each other.
• After step (3), the warning collapses to a single line, and the Project column reveals each of the targets where the warning appears
• After step (4), the warning expands to match the behavior after step (2)

[CyrusNajmabadi]

@AmadeusW @kayle

[CyrusNajmabadi]

Note: prior to step 2 this is handled by another team. @AmadeusW @kayle do you know who owns populating the build diagnostics? we likely need to pull them in.

[kayle]

Looks like Project System

The Identifier property needs to be set for diagnostics to be merged:

[CyrusNajmabadi]

@tmeschter do you know who we can pull in here on the project system to fixup build-diagnostics so that they get properly collapsed in VS?

Currently when roslyn is responsible for diagnostics, i presume we do this work. But in the new LSP world, the project system just reports the diagnostics directly through LSP, and it will have to populate this data as well so that the experience is good.

@sharwell could you show images of hte "with/without" pull diagnostics to help motivate this? It would be good to see how bad it is when the diagnostics are duplicated/triplicated/etc. depending on the number of project flavors.

Thanks!

[CyrusNajmabadi]

@adrianvmsft @lifengl can you look into this for us. We really want to move to LSP pull diagnostics, but diagnostics/error-list is such a critical experience for us, we don't want to regress things in areas like this. Thanks!

[CyrusNajmabadi]

Tracked with https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1889583.

[CyrusNajmabadi]

Fixed with https://devdiv.visualstudio.com/DevDiv/_git/CPS/pullrequest/500445.