Function Unable to Fail: Breaks Macros

Question

Vim functions do not seem to be able to fail without spitting out 3 unnecessary lines. For example, take this set of functions and maps:

" NEXT / PREVIOUS
" ~~~~~~~~~~~~~~~
" n and N always search for matched pattern forwards and backwards (resp.)
" no more guessing!
function! s:searchNext(forward)
    try
        execute 'normal! '.(a:forward ? 'n' : 'N')
    catch /^Vim\%((\a\+)\)\=:E486/
        echohl ErrorMsg
        echon "\rE486: Pattern not found: ".@/
        echohl None
        " echoerr 'E486: Pattern not found: '.@/
        return
    endtry
    normal! zv
    redraw
    echon (a:forward ? '/' : '?').@/
endfunction
nnoremap n :call <sid>searchNext(v:searchforward ? 1 : 0)<bar>set hlsearch<cr>
nnoremap N :call <sid>searchNext(v:searchforward ? 0 : 1)<bar>set hlsearch<cr>

Now try opening a file with this in it:

foo
bar keepme 1

foo
bar

foo
bar keepme 2

foo
bar

foo
bar

foo
keepme bar 3

foo
bar

1 | let @a = '' | let @/ = 'keep'.'me' | let @q = 'n"Ad2k'
keepme .. run on previous line: ^y$:<c-r>"<cr>  then press @q at least 5 times

on the 5th time, the macro does not fail on the "n", so the text that would not
be yanked into @a with norm! n IS cut/yanked into @a

Follow the instructions.

---

The issue is that :echon doesn't fail. So, I tried to return 0 and return 1. This doesn't seem to make the function fail. I tried replacing the 3 lines (echohl .., echon .., echohl ..) with echoerr .. (the commented out bit), but this takes up three lines with two error messages:

Error detected while processing function <SNR>24_searchNext:
line    7:
E486: Pattern not found: keepme

and that--to me--is just unacceptable.

---

So, is there:

1. a way to make a function fail without :echoerr
   • it thouroughly annoys me that :echoerr throws an error itself .. ridiculous .. there should at least be an :echoerr that doesn't throw an error

or

2. a way to :echoerr without throwing an error or some way to achieve something similar

or

3. any other way of making the macro (or another nmap) fail when using a map that is bound to a function like this (restriction: you can only make it fail from within this function, itself).

Thanks,

Answer 1

...:echoerr without throwing an error or some way to achieve something similar?

Call it outside of a try block. Per :h :echoerr you're seeing this behavior...

When used inside a try conditional, the message is raised as an error exception

---

...make a function fail without :echoerr?

Use :throw?

Have you read all of the applicable Vim documentation? Besides the help for individual commands like :echoerr, :throw, :try, :catch, etc. there's this whole section: :h exception-handling.