How to add custom errorformat at the beginning of the list

Question

I added a custom errorformat in my .vimrc like this:

set errorformat+=ERROR:\ %f:%l:%c:\ error:\ %m

However, this doesn't work because an already existing format is matched first (incorrectly). In order to prioritize my own format I'd like to add it to the beginning of the errorformat list but haven't found a way to do so. I checked :h list but that didn't help or maybe I'm looking in the wrong spot. How can I achieve this?

Answer 1

Use set errorformat^=ERROR:\ %f:%l:%c:\ error:\ %m

For string option ^= would prepend given value to existing one.

See :h set^= for reference.