Hammerspoon function to set default browser

init.lua

function setDefaultBrowser(appFileName, notify)
  local logger = hs.logger.new('defbr', 5)
  local app = hs.application.open('com.apple.systempreferences')
  local axapp = hs.axuielement.applicationElement(app)

  -- Attempt to open the menu until it successfully opens (returns true)
  hs.timer.waitUntil(function()
    return app:selectMenuItem({'View', 'General'})
  end, function()
    print('General group opened.')
    findPopup()
  end)

  function findPopup()
    local dwbPopup = nil
    -- Attempt to find the popup (combo box)
    hs.timer.doUntil(function() return dwbPopup end, function()
      axapp:elementSearch(function(msg, results)
        if results then dwbPopup = results[1] end
      end, function(e)
        return e:attributeValue('AXDescription') == 'Default Web Browser popup'
      end)
    end)
    hs.timer.waitUntil(function() return dwbPopup end, function()
      print('Popup found.')
      chooseAppFileName(dwbPopup)
    end)
  end

  function chooseAppFileName(dwbPopup)
    dwbPopup:performAction('AXShowMenu')
    dwbPopup:elementSearch(function(msg, results)
      local item = results[1]
      item:performAction('AXPress')
      notify()
    end, function(e)
      return e:attributeValue('AXTitle') == appFileName
    end)
  end
end

Re adding details, it's hinted at in the first line of the Notes (• This method utilizes coroutines to keep Hammerspoon responsive), but you're right, it's not clear and just mentions slow when includeParents is set. I'll give it some thought to see how best to re-word it -- I have some time coming up in the next couple of weeks that I plan to devote to Hammerspoon and will clarify it then.

Glad that it helps! I have a couple of tools I use when trying to narrow axuielement searches and I'm hoping to provide some wiki articles showing and discussing them during the same period.