fix(expert): don't crash on missing root_uri

[evnu]

Opening an .exs file outside of a mix project results in a crash as described in #397. As described in GenLSP.Structures.InitializeParams, the root_uri is allowed to be nil and must be handled accordingly. To avoid crashing on start up in such a case, this PR drops setting the workspace URI in this case. While this doesn't make expert fully functional in single-file mode, with this change allows debugging further problems in the case of root_uri not being set.

Fix #397.

[mhanberg]

@katafrakt can you take a gander at this

[katafrakt]

I tested this, it does not fatally crash, but there's quite a lot of other errors now.

13:37:20.357 [error] ** (FunctionClauseError) no function clause matching in XPExpert.ActiveProjects.active?/1
    (xp_expert 0.1.0-rc.0) lib/expert/active_projects.ex:72: XPExpert.ActiveProjects.active?(nil)
    (xp_expert 0.1.0-rc.0) lib/expert/state.ex:146: XPExpert.State.apply/2
    (xp_expert 0.1.0-rc.0) lib/expert.ex:277: XPExpert.apply_to_state/2
    (xp_expert 0.1.0-rc.0) lib/expert.ex:207: XPExpert.handle_notification/2
    (xp_gen_lsp 0.11.3) lib/gen_lsp.ex:600: anonymous fn/2 in XPGenLSP.handle_notification_sync/3
    (xp_telemetry 1.3.0) /Users/pawel.sw/dev/expert/apps/expert/deps/telemetry/src/telemetry.erl:324: :xp_telemetry.span/3
    (xp_gen_lsp 0.11.3) lib/gen_lsp.ex:599: XPGenLSP.handle_notification_sync/3
    (xp_gen_lsp 0.11.3) lib/gen_lsp.ex:502: XPGenLSP.loop/3

This is likely from new changes in #405 and seem to be caused by completion.

13:37:22.273 [error] ** (FunctionClauseError) no function clause matching in XPExpert.EngineApi.schedule_compile/2
    (xp_expert 0.1.0-rc.0) lib/expert/engine_api.ex:20: XPExpert.EngineApi.schedule_compile(nil, false)
    (xp_expert 0.1.0-rc.0) lib/expert/state.ex:214: XPExpert.State.apply/2
    (xp_expert 0.1.0-rc.0) lib/expert.ex:277: XPExpert.apply_to_state/2
    (xp_expert 0.1.0-rc.0) lib/expert.ex:207: XPExpert.handle_notification/2
    (xp_gen_lsp 0.11.3) lib/gen_lsp.ex:600: anonymous fn/2 in XPGenLSP.handle_notification_sync/3
    (xp_telemetry 1.3.0) /Users/pawel.sw/dev/expert/apps/expert/deps/telemetry/src/telemetry.erl:324: :xp_telemetry.span/3
    (xp_gen_lsp 0.11.3) lib/gen_lsp.ex:599: XPGenLSP.handle_notification_sync/3
    (xp_gen_lsp 0.11.3) lib/gen_lsp.ex:502: XPGenLSP.loop/3

This I think is from formatting request. I haven't seen it earlier, so I'm not sure whats causing it.

Go to definition, references, code actions do not work, but I haven't seen errors related to them.

[katafrakt]

Still an improvement from current main. I think it's worth merging, even if does not solve everything.

This is the error I'm getting on main, but it does not happen on this branch. All the errors I mentioned above are in logs, but are not thrown in the editor.

[mhanberg]

So it looks like this stop it from crashing, but will still output lots of warning because it's running in an implicitly degraded state.

There will be further work to fulfill #398

[katafrakt]

That's how I understood what we want for 0.1 - not have a visible crash, but getting everything to work is out of this scope and moved to 0.2.