Fix Spurious Compilation Errors

[kaeluka]

Closes #3220

issue: https://github.com/github/codeql-core/issues/4654

This notifies the language server of newly downloaded packs once a pack is added to the current ql pack, or a pack's dependencies are installed.

This is the user facing behaviour I observed:

• ✅ creating a query pack and example.ql file using the skeleton wizard:
  • works as expected
• ✅ creating a query pack and ql file manually, then installing the ql pack's dependencies using the vs code command palette:
  • works: this removes the spurious compilation errors, even in open files.
  • ⚠️ the price of supporting that is that we restart the language server each time a pack is added or a pack's dependencies are installed. There might be cheaper solutions, but I don't know them. If the reviewers don't know of a cheaper solution: I think this overhead is worth it because pack add/pack install are rare operations and the user would likely have to manually restart or reload vs code instead to make it work.

Dear Reviewer

• This is a PoC that works for me.
• I had to inject the language server reference into the cli server.
  • I'm not sure if this would be considered a design violation. I'd appreciate some feedback.
  • If that's a problem, I could refactor this to break the dependency using dependency injection. Meaning: pass in a lambda function that does the notification.
• Maybe, the same effect could also be achieved by different means (like watching the ~/.codeql/packages subdirectories, ...). Chances are, there's room for improvement.

[kaeluka]

Koen pointed out this could be generalized: https://github.com/github/codeql-core/issues/4654#issuecomment-2506073240 -> draft mode

[koesie10]

I've left a few small comments, but I'll leave a full review of this approach to someone that is more familiar with the language server/CLI interactions.

[kaeluka]

Thank you for your comments <3 I'll work on them next week.

[kaeluka]

Thanks @koesie10 and @aeisenberg for your reviews! They've increased my confidence, as well as made the PR shorter and simpler :) This commit is the result: 17542d1

[koesie10]

Thanks, LGTM! I've also tested this using the reproduction steps in the public and internal issues and it doesn't show any compilation errors once the pack has been installed.

Can you please add "Closes #3220" to the issue description since this PR fixes that issue?

[kaeluka]

I've also tested this using the reproduction steps in the public and internal issues and it doesn't show any compilation errors once the pack has been installed.

Thanks for taking the time to do that, I appreciate it!

Can you please add "Closes #3220" to the issue description since this PR fixes that issue?

done!