Refactor the lua dependency checking.

This is in preparation for the next step, which is to find a suitable
lua interpreter, rather than just erroring when an interpreter is found
but doesn't have the necessary dependencies.

Helped-by: John Szakmeister <john@szakmeister.net>

2 files changed, 44 insertions, 20 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b58f717eb6..97b21d1f14 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -98,29 +98,15 @@ if(NOT EXISTS ${LUA_PRG})
   find_program(LUA_PRG lua)
 endif()
 
-if(EXISTS ${LUA_PRG})
-  message(STATUS "Using the lua interpreter ${LUA_PRG}")
-else()
-  message(FATAL_ERROR "A lua interpreter is required for building the Neovim")
-endif()
-
-execute_process(COMMAND ${LUA_PRG} -e "require('lpeg')"
-                RESULT_VARIABLE LUA_LPEG_MISSING
-                ERROR_QUIET)
+include(LuaHelpers)
+set(LUA_DEPENDENCIES lpeg cmsgpack)
+check_lua_deps(${LUA_PRG} "${LUA_DEPENDENCIES}" LUA_PRG_WORKS)
 
-if(${LUA_LPEG_MISSING})
-  message(FATAL_ERROR
-          "The 'lpeg' lua package is required for building Neovim")
+if(NOT LUA_PRG_WORKS)
+  message(FATAL_ERROR "A suitable Lua interpreter was not found")
 endif()
 
-execute_process(COMMAND ${LUA_PRG} -e "require('cmsgpack')"
-                RESULT_VARIABLE LUA_MSGPACK_MISSING
-                ERROR_QUIET)
-
-if(${LUA_MSGPACK_MISSING})
-  message(FATAL_ERROR
-         "The 'cmsgpack' lua package is required for building Neovim")
-endif()
+message(STATUS "Using the Lua interpreter ${LUA_PRG}")
 
 add_subdirectory(config)
 add_subdirectory(src/nvim)
diff --git a/cmake/LuaHelpers.cmake b/cmake/LuaHelpers.cmake
new file mode 100644
index 0000000000..b1e67e0ca7
--- /dev/null
+++ b/cmake/LuaHelpers.cmake
@@ -0,0 +1,38 @@
+#
+# Functions to help checking for a Lua interpreter
+#
+
+# Check if a module is available in Lua
+function(check_lua_module LUA_PRG_PATH MODULE RESULT_VAR)
+  execute_process(COMMAND ${LUA_PRG_PATH} -e "require('${MODULE}')"
+    RESULT_VARIABLE module_missing
+    ERROR_QUIET)
+  if(module_missing)
+    message(STATUS
+      "[${LUA_PRG_PATH}] The '${MODULE}' lua package is required for building Neovim")
+    set(${RESULT_VAR} False PARENT_SCOPE)
+  else()
+    set(${RESULT_VAR} True PARENT_SCOPE)
+  endif()
+endfunction()
+
+# Check Lua interpreter for dependencies
+function(check_lua_deps LUA_PRG_PATH MODULES RESULT_VAR)
+  # Check if the lua interpreter at the given path
+  # satisfies all Neovim dependencies
+  message(STATUS "Checking Lua interpreter ${LUA_PRG_PATH}")
+  if(NOT EXISTS ${LUA_PRG_PATH})
+    message(STATUS
+      "[${LUA_PRG_PATH}] file not found")
+  endif()
+
+  foreach(module ${MODULES})
+    check_lua_module(${LUA_PRG_PATH} ${module} has_module)
+    if(NOT has_module)
+      set(${RESULT_VAR} False PARENT_SCOPE)
+      return()
+    endif()
+  endforeach()
+
+  set(${RESULT_VAR} True PARENT_SCOPE)
+endfunction()