How can I append to a terminal buffer in vimscript?

Question

I am trying to implement a vimscript function which appends to a terminal buffer. It works when I write this as a single mapping which uses the normal mode 'a' command to append:

nnoremap <Leader>glq :tabnew<CR>:terminal<CR>:set ft=instaflog<CR>als<CR>

But I want this in a function to make the code clearer. However, using append() or insert() I get the error stating that the terminal buffer is not modifiable, which I guess is strictly true, but every keypress is passed on to the terminal. So far, I have:

function! TerminalSomething() abort
  tabnew
  terminal
  set ft=instaflog
  startinsert
  execute "normal! Ayyy" 
endfunction

But the 'yyy' text doesn't appear; that execute line apparently does nothing for terminal buffers, even though it works for all other buffer types.

Answer 1

This sounds like a job for feedkeys(). What makes me think that^* is the fact that you got the response you wanted when the command was included in a mapping. Looking at the first sentence of the documentation for the function:

Characters in {string} are queued for processing as if they come from a mapping or were typed by the user.

(Emphasis is mine.)

So instead of

execute "normal! als" 

...try...

call feedkeys("als\<CR>")

Be sure to read the docs as there are some important things to be aware of there such as the need to escape special keys/keycodes as is done here with <CR>.

*_{Besides the fact that whenever output seems to be ignored I usually try feedkeys() as a first step.}