Regex pattern to clear all problems of a task owner

[justingrant]

Some compilers or build pipelines (e.g. create-react-app) emit different output if there are no errors vs. if there are 1+ errors or warnings. This makes it difficult to build problem matchers because start/end patterns need to have both a "errors" and a "no errors" version inside the same regex.

It would be better if there were a new pattern in task config (e.g. clearAllPattern) that, if found, would clear all existing problems from the current owner.

For non-background tasks this would be straightforward-- if the pattern is matched, then clear all problems from the owner and ignore all problems from the currently-executing task until the task exits.

For background tasks, it'd be a little more complicated:

1. clear all problems from the owner
2. reset the state if it's currently after a beginsPattern but before an endsPattern
3. wait until the next beginsPattern before logging more problems.

As a side effect, this feature would provide an escape hatch for users who want to clear problems by running a task (#50448), because you could create a task with a clearAllPattern that always matches.

[acdha]

I believe I have a good use-case for this improvement. I have task configuration for Gulp which captures SCSS & JS compilation errors. Most of the time this works but there's a race condition of some sort where something (maybe focus switching?) causes it to run while I'm in the middle of typing something and it reports an error (e.g. display: <EOL> must have a value) which will never clear without closing and re-opening the window, even though subsequent runs will have the usual error/fix/clear cycle.

There's probably some way to fix whatever condition causes the initial trigger but that seems like it would be a lot more complicated than having the task simply be able to say “any time we start a run, clear every previously-reported problem from this task”.