From 7faa6c41c89f1c5d48f92a436ed690bc7ce6ea85 Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Mon, 7 Oct 2019 17:42:40 +0200
Subject: [PATCH] cmake: only set LUA_PRG with successful check (#11172)

This is relevant for when using `USE_BUNDLED_LUAJIT=ON` with
`USE_BUNDLED_LUAROCKS=OFF`, and then building without the necessary modules
being installed/activated there yet: it would check the other (system) "lua"
interpreters also, and in case all failed keep the `LUA_PRG` in the cache for
the last failed entry - making it not re-check the previous ones on the next
build (after you might have activated your custom LuaRocks installation).

Only setting LUA_PRG if the check was successful handles the case better where
it is configured already - we should not try to re-configure it then.
---
 CMakeLists.txt | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1b6ba45820..98a32a116b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -487,18 +487,19 @@ include(LuaHelpers)
 set(LUA_DEPENDENCIES lpeg mpack bit)
 if(NOT LUA_PRG)
   foreach(CURRENT_LUA_PRG luajit lua5.1 lua5.2 lua)
-    # If LUA_PRG is set find_program() will not search
-    unset(LUA_PRG CACHE)
+    unset(_CHECK_LUA_PRG CACHE)
     unset(LUA_PRG_WORKS)
-    find_program(LUA_PRG ${CURRENT_LUA_PRG})
+    find_program(_CHECK_LUA_PRG ${CURRENT_LUA_PRG})
 
-    if(LUA_PRG)
-      check_lua_deps(${LUA_PRG} "${LUA_DEPENDENCIES}" LUA_PRG_WORKS)
+    if(_CHECK_LUA_PRG)
+      check_lua_deps(${_CHECK_LUA_PRG} "${LUA_DEPENDENCIES}" LUA_PRG_WORKS)
       if(LUA_PRG_WORKS)
+        set(LUA_PRG "${_CHECK_LUA_PRG}" CACHE FILEPATH "Path to a program.")
         break()
       endif()
     endif()
   endforeach()
+  unset(_CHECK_LUA_PRG CACHE)
 else()
   check_lua_deps(${LUA_PRG} "${LUA_DEPENDENCIES}" LUA_PRG_WORKS)
 endif()