Avoid reentrance when in printReplacement

hs.ipc replaces the print function with one that calls the original,
but also sends anything that print prints to any of the remote
connections. If you have debugging enabled, that means that the moment
the remote connection is created, a bunch of print statements are sent
to the this connection.

The problem I had is that my use of hs (command) was simply to send a
message to the screen:

     warning () {
        hs -c "hs.alert.show('$1')" > /dev/null
        echo "$1"
     }

The connection was so ephemeral, than I frequently got errors (related
to the client no long existing) which were tried to be send to the
client... so I ended with the following messages:

   2023-12-31 22:00:02: 22:00:02 ERROR: LuaSkin: hs.ipc callback is
   being called recursively. Check your callback function, it is
   triggering further IPC messages. This message was triggered after
   reaching 5 recursive callbacks.

This code avoid recursion for the same IPC client by keeping a counter
of how many times the client has entered the critical region.

extensions/ipc/ipc.lua

@@ -33,19 +33,52 @@ local MSG_ID = {
     CONSOLE    =  3,    -- cloned console output
 }
 
+-- avoid printReplacement to be reentrant
+-- otherwise errors might cascade into lots of recursive prints
+module.insidePrintInstances = {}
+
+module.print_enter = function(instance)
+  val = module.insidePrintInstances[instance] or 0
+  module.insidePrintInstances[instance] = val + 1
+end
+
+module.print_exit = function(instance)
+  -- make sure instance exists
+  if module.insidePrintInstances[instance] then
+    module.insidePrintInstances[instance] = module.insidePrintInstances[instance] - 1
+    if module.insidePrintInstances[instance] == 0 then
+      module.insidePrintInstances[instance] = nil
+    end
+  end
+end
+
+module.print_inside = function(instance)
+  val = module.insidePrintInstances[instance]
+  return val and val > 0
+end
+
 local originalPrint = print
 local printReplacement = function(...)
     originalPrint(...)
-    for _,v in pairs(module.__registeredCLIInstances) do
+    for i,v in pairs(module.__registeredCLIInstances) do
+      originalPrint(string.format("to print instance [%s]", i))
         if v._cli.console and v.print and not v._cli.quietMode then
 --            v.print(...)
 -- make it more obvious what is console output versus the command line's
+
+          if module.print_inside(i) then
+            originalPrint(string.format("Instance of [%s] already recursing [%d] times, do not do ",
+                i, module.insidePrintInstances[i]))
+          else
+            module.print_enter(i)
             local things = table.pack(...)
             local stdout = (things.n > 0) and tostring(things[1]) or ""
             for i = 2, things.n do
-                stdout = stdout .. "\t" .. tostring(things[i])
+              stdout = stdout .. "\t" .. tostring(things[i])
             end
             v._cli.remote:sendMessage(stdout .. "\n", MSG_ID.CONSOLE)
+            module.print_exit(i)
+          end
         end
     end
 end