Dynamically toggle formatoptions based on input

Question

Question: Is there a way to control the indentation + comment leader input, when adding a new line?

Details: I am trying to set formatoptions-=cro when inserting a new line (in specific syntax region). I tried using the autocommands InsertEnter and InsertCharPre, but both are too generic for my use case and I cannot figure out how to only operate on entering an <Enter> when in insert and o/O when in normal mode.

(InsertCharPre does not trigger on new line insertions, and InsertEnter also triggers on typing a/A/i/I.) What am I missing? Any pointers will be greatly appreciated. :)

Edit: I forgot to mention, that my intention is to dynamically add/suppress a comment-continuation insertion on new line insertions (depending on the syntax region).

Answer 1

tl;dr: I was looking for :set comments+=f:{string}.

Details: My usecase is, that every time I have the following style starting comment (in a javascript file) and I type <Enter>/o/O it should not yield an auto-indented + auto-commented next line on enter:

/*::<Enter>
 * <-- I wanted to suppress this

The solution to this was to :set comments+=f:/*::, which sets the comment to not be continued with any mb:{string} comments on the next line. See :help comments for further details.

Note: If you still have an answer to "How do I trigger a function on adding a new line?" feel free to answer. ✌️