Why mapping enter to nop makes the last search to be repeated?

Question

I use the enter key as my leader:

nnoremap <cr> <nop> " To avoid moving the cursor
let mapleader="\<enter>"

So far so good. To have the same behavior on Dirvish I need to remap enter to <nop> again, otherwise when I press it, it navigates to the path under the cursor (which I don't need because gf is already burned in my brain):

augroup DirvishSetUp
    autocmd!
    autocmd FileType dirvish
        \ nnoremap <buffer> <cr> <nop> |
        \ nnoremap <buffer> <silent> gf :call dirvish#open('edit', 0)<cr>
augroup END

It works as expected, except for an annoying little detail: If I searched something previously, on any buffer, and press the enter key on the Dirvish one and wait, the last search gets repeated. :nmap shows the following for <cr>:

n <CR> *@<nop><Space>
n <CR> * <Nop>

Why is this happening? (Not sure if relevant, but this is on Neovim 0.4.3)

Answer 1

The problem, as user938271 explains, is that by inadvertently including a space in the {rhs} of your mapping, you prevent <nop> from acting like a no-op, and instead it becomes a literal string of keystrokes: <, n, o, p, >.

In the resulting mapping, The < does nothing, and the following n repeats the last search.

This behaviour can be inferred from the documentation for <Nop>:

An easier way to get a mapping that doesn't produce anything, is to use "<Nop>" for the {rhs}.

Note that it doesn't say "in the {rhs}", but instead "for the {rhs}". This implies that if the {rhs} is not exactly <Nop>, but instead includes <Nop>, the special behaviour will not be triggered. (This wording could probably be improved, and I'm sure Bram would welcome a pull request for this.)

The space is included in the mapping is the one between the <nop> and the bar: |. Vim includes this in the mapping because it has no way of knowing this isn't what you intend. Thus, to fix the issue, change that line to:

\ nnoremap <buffer> <cr> <nop>|

Note that there are three clues that this is what was happening in the output of :nmap <CR>:

1. In the first, buffer-local, mapping, <Space> is included,
2. In that mapping the output has a lower-cased <nop> (what you typed) instead of the upper-cased <Nop> (Vim's notation for the special feature).
3. This is not visible in the paste, but it is inside Vim: the <nop> in the first mapping is highlighted differently from the <Nop> in the second one. The latter is has special highlighting to indicate it is not a series of keystrokes, but instead a single <Nop>.