A way to trigger user-visible error/warning/info pop-up outside of an ErrorResponse

[polinasok]

When we get an error while responding to a request, we can return an ErrorResponse and set showUser to get a very visible error pop-up.

Sending an ErrorResponse not tied to a request (e.g. a dup of the most recent response) is ignored (golang/vscode-go#182). OutputEvents let us write to the DEBUG CONSOLE and have a different colors depending on our choice of category ("stdout", "stderr", etc). Except, these kind of message tend to get overlooked in the ocean of logging and other output, especially if otherwise things look normal (e.g. microsoft/vscode-go#2783). In other cases, we need to communicate a user-visible message/warning while also sending a successful response (e.g. golang/vscode-go#787, where a next request gets cancelled by user request for a breakpoint, so we want to send a successful breakpoint response while also explaining the user that their action cancelled the pending next request).

If this requires a DAP spec change (as opposed to using a special category string with an OutputEvent or allowing orphaned ErrorResponses), I am happy to file an issue there as well.

[weinand]

In general we are reluctant to support anything in DAP that "drives the UI" since only the client owns the UI and "drives" it.
So out-of-context notifications is not something we want to support easily...

But here are two suggestions:

• create a DAP feature request where we can start a discussion about this independent from VS Code.
• try to solve the problem in your extension code: your extension can make assumptions about the VS Code debugger UI and there is enough UI API to do whatever you want.