better integration with vscode

[bobzhang]

• For watch mode, vscode needs a begin pattern, end pattern pair
• For error exits, it would be nice to have an indicator

[avsm]

Are these configurable in vscode? The error markers in this PR are kind of shouty and not in the normal dune style.

[Khady]

Yes, it is possible to create a tasks.json file to specify the patterns for beginning and end. In my current setup it looks like this (works only because I call dune from a makefile).

            "beginsPattern": "dune build .*",
            "endsPattern": "make\\[1\\]: Leaving directory '.*"

[rgrinberg]

The above isn't all that great either. $ dune runtest isn't picked up by this for example.

[ghost]

Can we detect if we are being run by vscode?

[bobzhang]

Would it do any harm to have a clear delimiter in general? Currently the dune output is verbose, without a decent integration with editor, you have to search pages to find the location..
Note you can pick a nicer message.
There are some work around as @Khady , creating a wrapper around dune, but it is not pretty and slows down

[ghost]

The capital letter are a bit loud, so if it only works in vscode, it seems better to use them only when running under vscode.

Could you try passing --display progress to dune when running under vscode and see if it improves the output? progress is the best output mode: it's quiet but still shows progression. However, it only works if the output is a terminal or when running inside emacs. If it works under vscode as well, then we can enable it when running inside vscode.

[bobzhang]

see #1733

[ghost]

?