How can I run a java file from a neovim terminal using a remap

Question

For a bit of background, I'm trying to set up a function that runs a java file in Neovim, I've tried using the following autocmd:

vim.api.nvim_create_autocmd(
  { "FileType" },
  {
    command = "map <buffer> <F5> :w<cr>:exec '!java' shellescape(@%,1)<cr>",
    pattern = { 'java' },
    group = RunFile,
  }
)

which does work, however if I ask for input (effectively interrupting the program) it gives me an error.

Exception in thread "main" java.util.NoSuchElementException: No line found
        at java.base/java.util.Scanner.nextLine(Scanner.java:1651)
        at com.mycompany.app.CoolApp.main(CoolApp.java:15)

shell returned 1

Now maybe there's an easier solution to my problem (if so please tell) but the solution I came up with is to start a new terminal using :terminal and running an equivalent of java % there.

trying that very literally map <buffer> <F5> :w<cr>:terminal 'java %' gives me the error no such file or directrory, which doesn't make sense to me because it perfectly gives me the path from where I opened neovim to the .java file (for the record it also doesn't work if I start from my home directory, or even from root), if I try doing things manually though (first :terminal, then typing java path/to/file.java) then it does work. I'm very confused, does anyone have any ideas?

Answer 1

Quotes in the [command] of :terminal will be passed to the shell. As there's obviously no file called 'java %' (% will be expanded to the name of the current file, though), an error "no such file or directory" is raised.

The solution is to simply remove the quotes and use this mapping:

:map <buffer> <F5> :w<CR>:terminal java %<CR>

Following the famous rule of thumb

If you don't know that you don't want :nnoremap, you want :nnoremap.

you want :nnoremap instead of :map. While we're on it, we might as well make it a little more idiomatic by using <Cmd> instead of : and <Bar> to separate commands. So the final mapping would be:

:nnoremap <buffer> <F5> <Cmd>write <Bar> terminal java %<CR>

See :help :terminal, :help :nnoremap, :help <Cmd> and the somewhat dull looking :help :|.