wp: support loading optional modules

-some modules will not be available during runtime, due to
  external dependencies.
 -these modules can now be marked optional.
 -loading of these optional modules will be attempted and if
  they are not available, wp will recover and will not be
  terminated.

modules/module-lua-scripting/config.c

@@ -63,10 +63,23 @@ load_components (lua_State *L, WpCore * core, GError ** error)
       args = wplua_lua_to_gvariant (L, -1);
     }
 
-    wp_debug ("load component: %s (%s)", component, type);
+    gboolean optional = FALSE;
+    if (lua_getfield (L, table, "optional") == LUA_TBOOLEAN) {
+      optional = lua_toboolean (L, -1);
+    }
 
-    if (!wp_core_load_component (core, component, type, args, error))
-      return FALSE;
+    wp_debug ("load component: %s (%s) optional(%s)",
+     component, type, (optional ? "true" : "false"));
+
+    g_autoptr (GError) load_error = NULL;
+    if (!wp_core_load_component (core, component, type, args, &load_error)) {
+      if (!optional) {
+        g_propagate_error (error, g_steal_pointer (&load_error));
+        return FALSE;
+      } else {
+        wp_message ("%s", load_error->message);
+      }
+    }
 
     /* clear the stack up to the key */
     lua_settop (L, key);

src/config/bluetooth.lua.d/30-bluez-monitor.lua

@@ -8,5 +8,5 @@ function bluez_monitor.enable()
     rules = bluez_monitor.rules,
   })
 
-  load_module("logind")
+  load_optional_module("logind")
 end

src/config/common/00-functions.lua

@@ -1,12 +1,21 @@
 components = {}
 
 function load_module(m, a)
+  assert(type(m) == "string", "module name is mandatory, bail out");
   if not components[m] then
     components[m] = { "libwireplumber-module-" .. m, type = "module", args = a }
   end
 end
 
+function load_optional_module(m, a)
+  assert(type(m) == "string", "module name is mandatory, bail out");
+  if not components[m] then
+    components[m] = { "libwireplumber-module-" .. m, type = "module", args = a, optional = true }
+  end
+end
+
 function load_pw_module(m)
+  assert(type(m) == "string", "module name is mandatory, bail out");
   if not components[m] then
     components[m] = { "libpipewire-module-" .. m, type = "pw_module" }
   end