Errors from task with same owner as extension don't propagate to the EH

[jrieken]

@jrieken, I was trying to find the source of issue, so here is what I found

First, I found that DiagnosticCollection.set is not called when kicking watch task
However, it is called from ExtHostDiagnostics.$acceptMarkersChange without entries (clearing call) when task is terminated, for not opened files URIs

So, I checked what happens in MainThreadDiagnostics._forwardMarkers and it turns out that all markers always get filtered out there (even for opened files) because typescript exists in _activeOwners, so data array doesn't get filled, and this._proxy.$acceptMarkersChange(data); is not called

However, when a file is opened, DiagnosticCollection.set is called from somewhere else (not from ExtHostDiagnostics.$acceptMarkersChange and I didn't found from where), before the MainThreadDiagnostics._forwardMarkers call

So, in conclusion, collection is feeded from somewhere by DiagnosticCollection.set for opened files, and MainThreadDiagnostics._forwardMarkers also called after that, but never transmits markers further

I wanted to check how it behaves through codespaces extension for comparison, but it doesn't connects from OSS build

Originally posted by @n-gist in #245092 (comment)

[jrieken]

and it turns out that all markers always get filtered out there (even for opened files) because typescript exists in _activeOwners, so data array doesn't get filled, and this._proxy.$acceptMarkersChange(data); is not called

This is because the task system can reuse owners (which extensions cannot). The idea is to allow tasks to report errors, e.g for all TS files, but to let TS itself overwrite those with its own errors. That's implemented with the owner-reuse and in consequence makes us not propagate errors back to the EH

[n-gist]

Probably then MainThreadDiagnostics should manage own markers lists for each owner, forwarding the ones by priority? Because, when it receives a clearing call for markers of the most prioritized layer, it should check if there is still markers exists, on underlying layers. Like, when a file editor is closed, and extension clears markers for closed file, it should check if there is markers from the task exists, and forward them, instead of forwarding a clearing. Or check how it is implemented for Problems view, and replicate/reuse that? Just thinking, I'm sure you know better how it should be

Interesting, why it works normally for repository opened through codespaces extension. Does the markers from tasks get the extension owner tag because they are delivered over codespaces extension? Just wondering if this doesn't creates other issues because of such difference. I didn't test this, but it could overwrite markers disregarding their source, just taking those comes last, because TS extension markers and task markers may have identical owner sign, like 'typescript' and, maybe more importantly, both sit on extension layer, so it needs additional criteria to decide which may overwrite the other