daemon/engine: syntactic sugar for module ‘get’, ‘set’ properties

if the module declares such properties, they can be accessed
by treating module as a table, e.g.

hints[‘localhost’] = ‘127.0.0.1’
hints.hostname = ‘192.168.1.1.
print(hints.localhost)

equals to:
hints.set(‘localhost 127.0.0.1’)
hints.set(‘hostname 192.168.1.1’)
print(hints.get(‘localhost’))

daemon/engine.c

@@ -259,6 +259,30 @@ void engine_stop(struct engine *engine)
 	uv_stop(uv_default_loop());
 }
 
+/** Register module properties in Lua environment */
+static int register_properties(struct engine *engine, struct kr_module *module)
+{
+	lua_newtable(engine->L);
+	if (module->config != NULL) {
+		REGISTER_MODULE_CALL(engine->L, module, module->config, "config");
+	}
+	for (struct kr_prop *p = module->props; p->name; ++p) {
+		if (p->cb != NULL && p->name != NULL) {
+			REGISTER_MODULE_CALL(engine->L, module, p->cb, p->name);
+		}
+	}
+	lua_setglobal(engine->L, module->name);
+
+	/* Register module in Lua env */
+	lua_getglobal(engine->L, "modules_register");
+	lua_getglobal(engine->L, module->name);
+	if (l_sandboxcall(engine->L, 1) != 0) {
+		lua_pop(engine->L, 1);
+	}
+
+	return kr_ok();
+}
+
 int engine_register(struct engine *engine, const char *name)
 {
 	if (engine == NULL || name == NULL) {
@@ -278,16 +302,7 @@ int engine_register(struct engine *engine, const char *name)
 
 	/* Register properties */
 	if (module->props) {
-		lua_newtable(engine->L);
-		if (module->config != NULL) {
-			REGISTER_MODULE_CALL(engine->L, module, module->config, "config");
-		}
-		for (struct kr_prop *p = module->props; p->name; ++p) {
-			if (p->cb != NULL && p->name != NULL) {
-				REGISTER_MODULE_CALL(engine->L, module, p->cb, p->name);
-			}
-		}
-		lua_setglobal(engine->L, module->name);
+		return register_properties(engine, module);
 	}
 
 	return kr_ok();

daemon/lua/sandbox.lua

@@ -35,6 +35,25 @@ setmetatable(modules, {
 	end
 })
 
+-- Register module in Lua environment
+function modules_register(module)
+	-- Syntactic sugar for get() and set() properties
+	setmetatable(module, {
+		__index = function (t, k)
+			local  v = rawget(t, k)
+			if     v     then return v
+			elseif t.get then return t.get(k)
+			end
+		end,
+		__newindex = function (t, k, v)
+			local  old_v = rawget(t, k)
+			if not old_v and t.set then
+				t.set(k..' '..v)
+			end
+		end
+	})
+end
+
 -- Make sandboxed environment
 local function make_sandbox(defined)
 	local __protected = { modules = true, cache = true, net = true }

modules/README.rst

@@ -247,6 +247,15 @@ Once you load the module, you can call the module property from the interactive
 
 *Note* |---| this relies on function pointers, so the same ``static inline`` trick as for the ``Layer()`` is required for C/Go.
 
+Special properties
+------------------
+
+If the module declares properties ``get`` or ``set``, they can be used in the Lua interpreter as
+regular tables.
+
+.. warning: This is not yet completely implemented, as the module I/O format may change to map_t a/o
+            embedded JSON tokenizer.
+
 .. _`not present in Go`: http://blog.golang.org/gos-declaration-syntax
 .. _CGO: http://golang.org/cmd/cgo/
 .. _GCCGO: https://golang.org/doc/install/gccgo