How to avoid circular dependency in lua without global variables?

I'm using OpenResty and my app is setup as:

app/
   clients/
      photoClient.lua
   init.lua
   auth.lua

Let's say photoClient has both an unauthenticated and a authenticated endpoint (similar to an avatar endpoint that is accessible without logging in, but there may be private photos that you need to login first)

So in terms of dependencies, I have:

-- auth.lua

local photoClient = require('app.clients.photoClient')
-- this is used to show avatar on the login page

local auth = {}

auth.isAuthenticated = function ()
   -- logic to check authentication
end

return auth

and the client is

-- photoClient.lua
local auth = require('app.auth')

local photoClient = {}
photoClient.privateEndpoint = function()
   if (!auth.isAuthenticated()) {
       ngx.exit(403)
   }
   ...
end

photoClient.getAvator = function() {
   -- this is a public method used by auth
}

return photoClient

This is giving me a circular dependency issue. I've seen on other SO post that you can use global variables, i.e. to do photoClient = photoClient or require('app.clients.photoClient') but I do not want to use global variables and want to keep each module scoped to itself.

How can I do this?

Solution

Found the solution on LuaFlare Documentation by Kate Adams: basically add package.loaded[...] = your_module before you do return your_module to every file, i.e.

-- auth.lua
local auth = {}
package.loaded[...] = auth

local photoClient = require('app.clients.photoClient')

...

return auth


-- photoClient.lua
local photoClient = {}
package.loaded[...] = photoClient

local auth = require('app.auth')

...

return photoClient

Fixed the problem. Here is the link to the book's page for anyone who is interested to read more.