How to perform a reverse history search in ZSH’s vi-mode

In "vi" mode you can edit/navigate on the current shell prompt like a line in the vi editor. You can look at it like a one-line text file. Analogously in "emacs" mode you can edit/navigate the current command line using (some) of Emacs' shortcuts.

Example

For example in vi-mode you can do something like (in bash):

$ set -o vi
$ ls hello world
<ESC>
bbdw # results in
$ ls world

In emacs-mode you can hit e.g. Ctrl+A to jump at the start of a line (vi: Ctrl+[, 0 or ESC,0). You can turn on emacs mode via set -o emacs (in bash, ksh, zsh etc.).

Readline

A lot of interactive command line programs (including bash) use the readline library. Thus, you can configure which input mode to use (vi or emacs) and other options in one place such that every program using readline has the exact same editing/navigating interface.

For example my readline configuration looks like:

$ cat ~/.inputrc 
set editing-mode vi
set blink-matching-paren on

For example zsh/ksh does not use readline as far as I know, but also support vi/emacs modes that are very much like the bash/readline one.

Of course, the vi/emacs mode in a command line shell is just a subset of the complete editor feature set. Not every feature makes sense in a command line shell, and some features are more complicated to support than others.

Canonical Mode

Before vi/emacs modes of interactive command line shells 'were invented' your shell would use just the canonical mode of your terminal which only provides a limited set of editing commands (e.g. Ctrl+W to delete the last word.

Maybe like:

vicmd-accept() { prev_mode=vicmd; zle .accept-line }
viins-accept() { prev_mode=viins; zle .accept-line }
zle-line-init() { zle -K ${prev_mode:-viins} }
zle -N viins-accept
zle -N vicmd-accept
zle -N zle-line-init
bindkey -M viins \\r viins-accept
bindkey -M vicmd \\r vicmd-accept

Or even simpler:

accept-line() { prev_mode=$KEYMAP; zle .accept-line }
zle-line-init() { zle -K ${prev_mode:-viins} }
zle -N accept-line
zle -N zle-line-init