Nasal: support for module reload via command

This won’t work for all modules, depending on what inter-dependencies
exist.

src/Main/fg_commands.cxx

@@ -1036,6 +1036,17 @@ do_profiler_stop(const SGPropertyNode *arg, SGPropertyNode *root)
 #endif
 }
 
+static bool do_reload_nasal_module(const SGPropertyNode* arg, SGPropertyNode*)
+{
+    auto nasalSys = globals->get_subsystem<FGNasalSys>();
+    if (!nasalSys) {
+        SG_LOG(SG_GUI, SG_ALERT, "reloadModuleFromFile command: Nasal subsystem not found");
+        return false;
+    }
+
+    return nasalSys->reloadModuleFromFile(arg->getStringValue("module"));
+}
+
 
 ////////////////////////////////////////////////////////////////////////
 // Command setup.
@@ -1051,53 +1062,54 @@ do_profiler_stop(const SGPropertyNode *arg, SGPropertyNode *root)
 static struct {
   const char * name;
   SGCommandMgr::command_t command;
-} built_ins [] = {
-    { "null", do_null },
-    { "nasal", do_nasal },
-    { "pause", do_pause },
-    { "load", do_load },
-    { "save", do_save },
-    { "save-tape", do_save_tape },
-    { "load-tape", do_load_tape },
-    { "view-cycle", do_view_cycle },
-    { "view-push", do_view_push },
-    { "view-clone", do_view_clone },
-    { "view-last-pair", do_view_last_pair },
-    { "view-last-pair-double", do_view_last_pair_double },
-    { "view-new", do_view_new },
+} built_ins[] = {
+    {"null", do_null},
+    {"nasal", do_nasal},
+    {"nasal-module-reload", do_reload_nasal_module},
+    {"pause", do_pause},
+    {"load", do_load},
+    {"save", do_save},
+    {"save-tape", do_save_tape},
+    {"load-tape", do_load_tape},
+    {"view-cycle", do_view_cycle},
+    {"view-push", do_view_push},
+    {"view-clone", do_view_clone},
+    {"view-last-pair", do_view_last_pair},
+    {"view-last-pair-double", do_view_last_pair_double},
+    {"view-new", do_view_new},
     /*
     { "set-sea-level-air-temp-degc", do_set_sea_level_degc },
     { "set-outside-air-temp-degc", do_set_oat_degc },
     { "set-dewpoint-sea-level-air-temp-degc", do_set_dewpoint_sea_level_degc },
     { "set-dewpoint-temp-degc", do_set_dewpoint_degc },
     */
-    { "property-toggle", do_property_toggle },
-    { "property-assign", do_property_assign },
-    { "property-adjust", do_property_adjust },
-    { "property-multiply", do_property_multiply },
-    { "property-swap", do_property_swap },
-    { "property-scale", do_property_scale },
-    { "property-cycle", do_property_cycle },
-    { "property-randomize", do_property_randomize },
-    { "property-interpolate", do_property_interpolate },
-    { "data-logging-commit", do_data_logging_commit },
-    { "log-level", do_log_level },
-    { "replay", do_replay },
+    {"property-toggle", do_property_toggle},
+    {"property-assign", do_property_assign},
+    {"property-adjust", do_property_adjust},
+    {"property-multiply", do_property_multiply},
+    {"property-swap", do_property_swap},
+    {"property-scale", do_property_scale},
+    {"property-cycle", do_property_cycle},
+    {"property-randomize", do_property_randomize},
+    {"property-interpolate", do_property_interpolate},
+    {"data-logging-commit", do_data_logging_commit},
+    {"log-level", do_log_level},
+    {"replay", do_replay},
     /*
     { "decrease-visibility", do_decrease_visibility },
     { "increase-visibility", do_increase_visibility },
     */
-    { "loadxml", do_load_xml_to_proptree},
-    { "savexml", do_save_xml_from_proptree },
-    { "xmlhttprequest", do_load_xml_from_url },
+    {"loadxml", do_load_xml_to_proptree},
+    {"savexml", do_save_xml_from_proptree},
+    {"xmlhttprequest", do_load_xml_from_url},
 
-    { "profiler-start", do_profiler_start },
-    { "profiler-stop",  do_profiler_stop },
-    
-    { "video-start", do_video_start },
-    { "video-stop", do_video_stop },
+    {"profiler-start", do_profiler_start},
+    {"profiler-stop", do_profiler_stop},
 
-    { 0, 0 }			// zero-terminated
+    {"video-start", do_video_start},
+    {"video-stop", do_video_stop},
+
+    {0, 0} // zero-terminated
 };
 
 

src/Scripting/NasalSys.cxx

@@ -800,7 +800,7 @@ public:
         _sys->gcRelease(_gcRoot);
     }
 
-    virtual bool operator()(const SGPropertyNode* aNode, SGPropertyNode * root)
+    bool operator()(const SGPropertyNode* aNode, SGPropertyNode* root) override
     {
         _sys->setCmdArg(const_cast<SGPropertyNode*>(aNode));
         naRef args[1];
@@ -1541,8 +1541,12 @@ bool FGNasalSys::createModule(const char* moduleName, const char* fileName,
     if (!naHash_get(_globals, modname, &locals))
         locals = naNewHash(ctx);
 
-    _cmdArg = (SGPropertyNode*)cmdarg;
+    // store the filename in the module hash, so we could reload it
+    naRef modFilePath = naNewString(ctx);
+    naStr_fromdata(modFilePath, (char*)fileName, strlen(fileName));
+    hashset(locals, "__moduleFilePath", modFilePath);
 
+    _cmdArg = (SGPropertyNode*)cmdarg;
     callWithContext(ctx, code, argc, args, locals);
     hashset(_globals, moduleName, locals);
 
@@ -1565,6 +1569,28 @@ void FGNasalSys::deleteModule(const char* moduleName)
     naFreeContext(ctx);
 }
 
+bool FGNasalSys::reloadModuleFromFile(const std::string& moduleName)
+{
+    if (!_inited || naIsNil(_globals)) {
+        return false;
+    }
+
+    naRef locals = naHash_cget(_globals, (char*)moduleName.c_str());
+    if (naIsNil(locals)) {
+        // no such module
+        return false;
+    }
+
+    naRef filePath = naHash_cget(locals, (char*)"__moduleFilePath");
+    if (naIsNil(filePath)) {
+        return false;
+    }
+
+    SGPath path = SGPath::fromUtf8(naStr_data(filePath));
+    deleteModule(moduleName.c_str());
+    return loadModule(path, moduleName.c_str());
+}
+
 naRef FGNasalSys::getModule(const std::string& moduleName) const
 {
     naRef mod = naHash_cget(_globals, (char*)moduleName.c_str());

src/Scripting/NasalSys.hxx

@@ -163,6 +163,8 @@ public:
      */
     static naRef getPropertyValue(naContext c, SGPropertyNode* node);
 
+    bool reloadModuleFromFile(const std::string& moduleName);
+
 private:
     void initLogLevelConstants();
 
@@ -176,6 +178,7 @@ private:
                std::string& errors);
     naRef genPropsModule();
 
+
 private:
     //friend class FGNasalScript;
     friend class FGNasalListener;