Edit a command, and then execute upon pressing a keybinding in zsh

I am trying to execute an arbitrary command upon the keybinding "Control Space" with zsh.
I have the following code

function space-run() {
    $BUFFER=" $BUFFER"
    zle reset-prompt
    zle accept-line
}

zle -N space-run
bindkey '^ ' space-run # bind to control space

In other words, I want to add a space before a command, and then execute it, because in my zsh configuration, a command beginning with a space does not get added to history.

The above code does not work, and it keep saying "command not found: ls=ls" if I typed ls and pressed Control Space.

I expected $BUFFER=" $BUFFER" would add the space, but I'm not sure what happens, because it clearly doesn't do that.

I am also not sure what zle reset-prompt does, or if it's needed there.

How should I fix my code so that I get the desired behavior?

This does not make sense.

$BUFFER=" $BUFFER"

Assume that BUFFER has the value ls. The line would be expanded into

"ls= ls"

and this would be interpreted as a command to be executed.

Variable name assignment in zsh has the syntax

NAME=value

Therefore in your case

BUFFER=" $BUFFER"