Selecting a Menu Item with Hammerspoon

I try to use Hammerspoon to open a new window in Firefox with the following script:

function newWindow() 
    local app = hs.application.find("Firefox")
    
    print(hs.inspect.inspect(app))
    print(app:title())
    print(app:bundleID())

    local item = app:findMenuItem("File")
    
    print(item)
end

hs.hotkey.bind({'alt', 'ctrl', 'cmd'}, 'n', newWindow)

While the script is able to find Firefox, it is not able to find the menu item I am looking for. But at the same time, I am able to use app:getMenuItems() to retrieve the whole menu structure.

Does anyone have an idea why or an working example for any application?

I am using MacOS Big Sur 11.2.3

Solution

I think what you are looking for is the app:selectMenuItem() method:

function newWindow() 
    local app = hs.application.find("Firefox")
    app:selectMenuItem({"File", "New Window"})
end
hs.hotkey.bind({'alt', 'ctrl', 'cmd'}, 'n', newWindow)

From the docs:

hs.application:selectMenuItem(menuitem[, isRegex]) -> true or nil

Selects a menu item (i.e. simulates clicking on the menu item)

Parameters:

menuitem - The menu item to select, specified as either a string or a table. See the menuitem parameter of hs.application:findMenuItem() for more information.
isRegex - An optional boolean, defaulting to false, which is only used if menuItem is a string. If set to true, menuItem will be treated as a regular expression rather than a strict string to match against

Returns:

True if the menu item was found and selected, or nil if it wasn't (e.g. because the menu item couldn't be found)

Notes:

Depending on the type of menu item involved, this will either activate or tick/untick the menu item

http://www.hammerspoon.org/docs/hs.application.html#selectMenuItem

-- EDIT --

To avoid multiple language menu structure you can also open the new window using the keyboard shortcut for that:

function newWindow() 
    local app = hs.application.find("Firefox")
    hs.eventtap.keyStroke({'cmd'}, 'N', nil, app)
end
hs.hotkey.bind({'alt', 'ctrl', 'cmd'}, 'n', newWindow)