Missing language service features for some projects in a solution if the project is up-to-date

[0x53A]

ref #3054 (comment)

In some projects nothing works at all (colors, completion, ...):

This occurs reliably in a large solution with ~60 projects, but is not reproducible when reduced.

The issue happens in multiple projects, the lowest project is one with 5 dependencies.
If I remove everything except these six projects from the solution, the error stops occurring, even though there should be no change from the view of these projects, so it is impossible for me to provide a reduced reproduction.

For me it looks like something completely unrelated in the solution fucks VS up.

This seems to be related to the up-to-date check:

• If I modify a file and restart VS, stuff works.
• If I build the solution and restart VS, stuff stops working. (Note that before the restart, stuff continues to work even after the build.)

maybe related: #3221

Note: Build always works fine, this is just tooling

[dsyme]

@0x53A I know you've said you can't make a public repro for this, but we'll really need one to make progress on it, unless we get lucky and find the bug by some other means (which is likely sooner or later)

(Also is this using latest nightly? thx)

[0x53A]

Edit: This was a red-herring.

So, I experimented a bit more.

Remember I said above that it works after a clean, and fails after a build?

I was able to reduce it to one dll with one large embedded resource (15MB). Something else in the VS stack seems to choke on that and then poisons something so that VF# fails.

* If I delete the dll and restart VS, everything works.
* If I keep the dll, but remove the embedded resources (using dnspy), then restart VS, everything works.

[dsyme]

@0x53A Interesting, thanks. Can you share that repro?

[0x53A]

No, because when I remove all other projects, the error stops happening.

The error still only happens in the large, 60 project solution.

The solution contains WinForms projects, WPF projects, WIX projects, C++/CLI projects, it must be one of these.

[dsyme]

@0x53A Thanks. Nasty bug, we should protect the Visual F# IDE tools (and Roslyn) from whatever is happening

[0x53A]

Only F# is affected, C# does not have any issues.

[cartermp]

Yikes, that sounds bad. cc @Pilchie this sounds troubling

[dsyme]

@cartermp We really need a standalone repro to make progress on this - if the bug is as described it could come from any of those project flavours

[cartermp]

Agreed. However, in the essence of narrowing the problem down...

@0x53A Is this using VS 2017 Update 2, or Update 3? About when would you say this issue started happening?

[0x53A]

@cartermp VS 2017 Update 2. I have the latest nightly, but have also seen this issue with a colleague, who does not have the nightly.

I'm not sure when it started, at first it was only an unimportant project, so I didn't bother.
That it's now worse is probably related to something changed in our solution (added projects, added references, whatever).

I can try to check old versions from source control, but there are many external references, and some of them are not checked-in, so it may not be trivial to build a version from half a year ago.

[cartermp]

Argh. Sorry to hear that. Maybe there's a way for someone at MS to look at your solution under an NDA or something? I honestly don't know how that process works if it exists. @Pilchie probably would know, though.

[0x53A]

The easiest way (for me :D) would be if you could look at it on my computer through TeamViewer or something like that.

Sending it out may also be possible, but I would probably need to ask my bosses' boss.

It's interesting that we seem to be the only ones hitting this issue, either no-one uses VS2017, or this is really one specific corner case.