AP_Scripting: Add alias suppport to the scripting generator

libraries/AP_Scripting/README.md

@@ -29,8 +29,8 @@ An example script is given below:
 ```lua
 function update () -- periodic function that will be called
   current_pos = Location()
-  AP_AHRS:get_position(current_pos)
-  distance = current_pos:get_distance(AP_AHRS:get_home()) -- calculate the distance from home
+  ahrs:get_position(current_pos)
+  distance = current_pos:get_distance(ahrs:get_home()) -- calculate the distance from home
   if distance > 1000 then -- if more then 1000 meters away
     distance = 1000;      -- clamp the distance to 1000 meters
   end

libraries/AP_Scripting/generator/description/bindings.desc

@@ -15,6 +15,7 @@ userdata Location method get_vector_from_origin_NEU boolean Vector3f
 
 include AP_AHRS/AP_AHRS.h
 
+singleton AP_AHRS alias ahrs
 singleton AP_AHRS method get_position boolean Location
 singleton AP_AHRS method get_home Location
 
@@ -25,7 +26,9 @@ userdata Vector3f field y float read write -FLT_MAX FLT_MAX
 userdata Vector3f field z float read write -FLT_MAX FLT_MAX
 
 include AP_Notify/AP_Notify.h
+singleton notify alias notify
 singleton AP_Notify method play_tune void string
 
 include AP_RangeFinder/AP_RangeFinder.h
+singleton RangeFinder alias rangefinder
 singleton RangeFinder method num_sensors uint8_t

libraries/AP_Scripting/generator/src/main.c

@@ -6,6 +6,7 @@
 #include <string.h>
 #include <unistd.h>
 
+char keyword_alias[]     = "alias";
 char keyword_comment[]   = "--";
 char keyword_field[]     = "field";
 char keyword_include[]   = "include";
@@ -505,7 +506,8 @@ void handle_userdata(void) {
 
 struct singleton {
   struct singleton *next;
-  char *name;
+  char *name;  // name of the C++ singleton
+  char *alias; // (optional) used for scripting access
   struct method * methods;
 };
 
@@ -538,12 +540,28 @@ void handle_singleton(void) {
   if (type == NULL) {
     error(ERROR_SINGLETON, "Expected an access type for userdata %s", name);
   }
-  if (strcmp(type, keyword_method) != 0) {
-    error(ERROR_SINGLETON, "Singletons only support method access types (got %s)", type);
+
+  if (strcmp(type, keyword_alias) == 0) {
+    if (node->alias != NULL) {
+      error(ERROR_SINGLETON, "Alias of %s was already declared for %s", node->alias, node->name);
+    }
+    const char *alias = next_token();
+    if (alias == NULL) {
+      error(ERROR_SINGLETON, "Missing the name of the alias for %s", node->name);
     }
+    node->alias = (char *)allocate(strlen(alias) + 1);
+    strcpy(node->alias, alias);
 
-  // method name
+    // ensure no more tokens on the line
+    if (next_token()) {
+      error(ERROR_HEADER, "Singleton contained an unexpected extra token: %s", state.token);
+    }
+    return;
+  } else if (strcmp(type, keyword_method) == 0) {
     handle_method(TRACE_USERDATA, node->name, &(node->methods));
+  } else {
+    error(ERROR_SINGLETON, "Singletons only support methods or aliases (got %s)", type);
+  }
 
 }
 
@@ -841,6 +859,8 @@ void emit_singleton_method(const struct singleton *data, const struct method *me
     arg = arg->next;
   }
 
+  const char *access_name = data->alias ? data->alias : data->name;
+
   fprintf(source, "int %s_%s(lua_State *L) {\n", data->name, method->name);
   fprintf(source, "    const int args = lua_gettop(L);\n");
   fprintf(source, "    if (args > %d) {\n", arg_count);
@@ -848,12 +868,12 @@ void emit_singleton_method(const struct singleton *data, const struct method *me
   fprintf(source, "    } else if (args < %d) {\n", arg_count);
   fprintf(source, "        return luaL_argerror(L, args, \"too few arguments\");\n");
   fprintf(source, "    }\n\n");
-  fprintf(source, "    luaL_checkudata(L, 1, \"%s\");\n\n", data->name);
+  fprintf(source, "    luaL_checkudata(L, 1, \"%s\");\n\n", access_name);
 
   // fetch and check the singleton pointer
-  fprintf(source, "    %s *singleton = %s::get_singleton();", data->name, data->name);
+  fprintf(source, "    %s *singleton = %s::get_singleton();\n", data->name, data->name);
   fprintf(source, "    if (singleton == nullptr) {\n");
-  fprintf(source, "        return luaL_argerror(L, args, \"%s not supported on this firmware\");\n", data->name);
+  fprintf(source, "        return luaL_argerror(L, args, \"%s not supported on this firmware\");\n", access_name);
   fprintf(source, "    }\n\n");
 
   // extract the arguments
@@ -1016,7 +1036,7 @@ void emit_loaders(void) {
   fprintf(source, "} singleton_fun[] = {\n");
   struct singleton * single = parsed_singletons;
   while (single) {
-    fprintf(source, "    {\"%s\", %s_meta},\n", single->name, single->name);
+    fprintf(source, "    {\"%s\", %s_meta},\n", single->alias ? single->alias : single->name, single->name);
     single = single->next;
   }
   fprintf(source, "};\n\n");
@@ -1054,7 +1074,7 @@ void emit_sandbox(void) {
   struct singleton *single = parsed_singletons;
   fprintf(source, "const char *singletons[] = {\n");
   while (single) {
-    fprintf(source, "    \"%s\",\n", single->name);
+    fprintf(source, "    \"%s\",\n", single->alias ? single->alias : single->name);
     single = single->next;
   }
   fprintf(source, "};\n\n");

libraries/AP_Scripting/lua_generated_bindings.cpp

@@ -264,10 +264,11 @@ int RangeFinder_num_sensors(lua_State *L) {
         return luaL_argerror(L, args, "too few arguments");
     }
 
-    luaL_checkudata(L, 1, "RangeFinder");
+    luaL_checkudata(L, 1, "rangefinder");
 
-    RangeFinder *singleton = RangeFinder::get_singleton();    if (singleton == nullptr) {
-        return luaL_argerror(L, args, "RangeFinder not supported on this firmware");
+    RangeFinder *singleton = RangeFinder::get_singleton();
+    if (singleton == nullptr) {
+        return luaL_argerror(L, args, "rangefinder not supported on this firmware");
     }
 
     const uint8_t data = singleton->num_sensors(
@@ -287,7 +288,8 @@ int AP_Notify_play_tune(lua_State *L) {
 
     luaL_checkudata(L, 1, "AP_Notify");
 
-    AP_Notify *singleton = AP_Notify::get_singleton();    if (singleton == nullptr) {
+    AP_Notify *singleton = AP_Notify::get_singleton();
+    if (singleton == nullptr) {
         return luaL_argerror(L, args, "AP_Notify not supported on this firmware");
     }
 
@@ -306,10 +308,11 @@ int AP_AHRS_get_home(lua_State *L) {
         return luaL_argerror(L, args, "too few arguments");
     }
 
-    luaL_checkudata(L, 1, "AP_AHRS");
+    luaL_checkudata(L, 1, "ahrs");
 
-    AP_AHRS *singleton = AP_AHRS::get_singleton();    if (singleton == nullptr) {
-        return luaL_argerror(L, args, "AP_AHRS not supported on this firmware");
+    AP_AHRS *singleton = AP_AHRS::get_singleton();
+    if (singleton == nullptr) {
+        return luaL_argerror(L, args, "ahrs not supported on this firmware");
     }
 
     const Location &data = singleton->get_home(
@@ -328,10 +331,11 @@ int AP_AHRS_get_position(lua_State *L) {
         return luaL_argerror(L, args, "too few arguments");
     }
 
-    luaL_checkudata(L, 1, "AP_AHRS");
+    luaL_checkudata(L, 1, "ahrs");
 
-    AP_AHRS *singleton = AP_AHRS::get_singleton();    if (singleton == nullptr) {
-        return luaL_argerror(L, args, "AP_AHRS not supported on this firmware");
+    AP_AHRS *singleton = AP_AHRS::get_singleton();
+    if (singleton == nullptr) {
+        return luaL_argerror(L, args, "ahrs not supported on this firmware");
     }
 
     Location & data_2 = *check_Location(L, 2);
@@ -352,6 +356,10 @@ const luaL_Reg AP_Notify_meta[] = {
     {NULL, NULL}
 };
 
+const luaL_Reg notify_meta[] = {
+    {NULL, NULL}
+};
+
 const luaL_Reg AP_AHRS_meta[] = {
     {"get_home", AP_AHRS_get_home},
     {"get_position", AP_AHRS_get_position},
@@ -370,9 +378,10 @@ const struct singleton_fun {
     const char *name;
     const luaL_Reg *reg;
 } singleton_fun[] = {
-    {"RangeFinder", RangeFinder_meta},
+    {"rangefinder", RangeFinder_meta},
     {"AP_Notify", AP_Notify_meta},
-    {"AP_AHRS", AP_AHRS_meta},
+    {"notify", notify_meta},
+    {"ahrs", AP_AHRS_meta},
 };
 
 void load_generated_bindings(lua_State *L) {
@@ -402,9 +411,10 @@ void load_generated_bindings(lua_State *L) {
 }
 
 const char *singletons[] = {
-    "RangeFinder",
+    "rangefinder",
     "AP_Notify",
-    "AP_AHRS",
+    "notify",
+    "ahrs",
 };
 
 const struct userdata {