check for optional module dependencies and don't build optional modul…

…es if not found

lcm-lua/meson.build

@@ -1,7 +1,5 @@
 lcm_lua_sources = ['init.c', 'lualcm_hash.c', 'lualcm_lcm.c', 'lualcm_pack.c', 'lua_ref_helper.c', 'utf8_check.c']
 
-lua_dep = dependency('lua')
-
 lcm_lua_lib = library('lcm-lua', lcm_lua_sources,
   c_args : '-Wextra',
   dependencies : [lcm_lib_dep, lua_dep],

lcm-python/meson.build

@@ -1,4 +1,3 @@
-pymod = import('python')
 py_installation = pymod.find_installation()
 python_site = py_installation.get_path('platlib').replace(py_installation.get_path('data') / '', '')
 python_include = py_installation.get_path('include')

meson.build

@@ -42,7 +42,10 @@ endif
 
 # Python
 if not get_option('lcm_enable_python').disabled()
-  subdir('lcm-python')
+  pymod = import('python', required : get_option('lcm_enable_python'))
+  if pymod.found()
+    subdir('lcm-python')
+  endif
 endif
 
 # Java (Work in progress)
@@ -55,7 +58,10 @@ endif
 
 # Lua
 if not get_option('lcm_enable_lua').disabled()
-  subdir('lcm-lua')
+  lua_dep = dependency('lua', required : get_option('lcm_enable_lua'))
+  if lua_dep.found()
+    subdir('lcm-lua')
+  endif
 endif
 
 # Disabled because require pro meson wizardry to support without user-defined functions