hammerspoon hyper key: capslock to escape _and_ cmd+ctrl+alt+shift

hyper.lua

print([[


HYPER

## install

Use karabiner-elements to bind capslock to F18

install hammerspoon

save this file as ~/.hammerspoon/hyper.lua

add `require 'hyper'` to ~/.hammerspoon/init.lua

## use

press capslock by itself to send escape.

or use it as a modifier:

It acts like command+option+ctrl+shift. All
the modifiers at once.

It's hard to type all the modifiers at once, so
app keyboard shortcuts almost never require you
to.

But it's still allowed in set-your-own-shortcut
fields!

You now have an extra modifier key _and_ an
extra escape key. Go nuts.
]])

-- A variable for the Hyper Mode
local k = hs.hotkey.modal.new({}, 'F17')

-- All of the keys, from here:
-- https://github.com/Hammerspoon/hammerspoon/blob/f3446073f3e58bba0539ff8b2017a65b446954f7/extensions/keycodes/internal.m
-- except with ' instead of " (not sure why but it didn't work otherwise)
-- and the function keys greater than F12 removed.
local keys = {
  "a",
  "b",
  "c",
  "d",
  "e",
  "f",
  "g",
  "h",
  "i",
  "j",
  "k",
  "l",
  "m",
  "n",
  "o",
  "p",
  "q",
  "r",
  "s",
  "t",
  "u",
  "v",
  "w",
  "x",
  "y",
  "z",
  "0",
  "1",
  "2",
  "3",
  "4",
  "5",
  "6",
  "7",
  "8",
  "9",
  "`",
  "=",
  "-",
  "]",
  "[",
  "\'",
  ";",
  "\\",
  ",",
  "/",
  ".",
  "§",
  "f1",
  "f2",
  "f3",
  "f4",
  "f5",
  "f6",
  "f7",
  "f8",
  "f9",
  "f10",
  "f11",
  "f12",
  "pad.",
  "pad*",
  "pad+",
  "pad/",
  "pad-",
  "pad=",
  "pad0",
  "pad1",
  "pad2",
  "pad3",
  "pad4",
  "pad5",
  "pad6",
  "pad7",
  "pad8",
  "pad9",
  "padclear",
  "padenter",
  "return",
  "tab",
  "space",
  "delete",
  "help",
  "home",
  "pageup",
  "forwarddelete",
  "end",
  "pagedown",
  "left",
  "right",
  "down",
  "up"
}

local printIsdown = function(b) return b and 'down' or 'up' end

-- sends a key event with all modifiers
-- bool -> string -> void -> side effect
local hyper = function(isdown)
  return function(key)
    return function()
      k.triggered = true
      local event = hs.eventtap.event.newKeyEvent(
	{'cmd', 'alt', 'shift', 'ctrl'},
	key, 
	isdown
      )
      event:post()
    end
  end
end

local hyperDown = hyper(true)
local hyperUp = hyper(false)

-- actually bind a key
local hyperBind = function(key)
  k:bind('', key, msg, hyperDown(key), hyperUp(key), nil)
end

-- bind all the keys in the huge keys table
for index, key in pairs(keys) do hyperBind(key) end

-- Enter Hyper Mode when F18 (Hyper/Capslock) is pressed
local pressedF18 = function()
  k.triggered = false
  k:enter()
end

-- Leave Hyper Mode when F18 (Hyper/Capslock) is pressed,
--   send ESCAPE if no other keys are pressed.
local releasedF18 = function()
  k:exit()
  if not k.triggered then
    hs.eventtap.keyStroke({}, 'ESCAPE')
  end
end

-- Bind the Hyper key
local f18 = hs.hotkey.bind({}, 'F18', pressedF18, releasedF18)

ERROR:   LuaSkin: hs.hotkey:enable() keycode: 103, mods: 0x0000, RegisterEventHotKey failed: -9878
ERROR:   LuaSkin: This hotkey is already registered. It may be a duplicate in your Hammerspoon config, or it may be registered by macOS. See System Preferences->Keyboard->Shortcuts

Answered my own question by a more exploration: I found out that on macOS (at least for some users) the F11 key is mapped to "Show Desktop" in the System -> Keyboard -> Shortcuts.

And since this hyper script will take over all the keys it was trying to bind onto that (despite the shortcut actually being Disabled in the System Preferences.

Not sure why it was still binding / giving this error.

I rebound the Show Desktop in the Preferences to crtl + option + cmd + f11 because, apparently, you can not set a keyboard shortcut to none once it is set in OSX 🙈.