Fix various lua bugs to prevent crashes

Source/PluginEditor.cpp

@@ -187,11 +187,17 @@ void OscirenderAudioProcessorEditor::updateCodeEditor() {
             codeEditors[i]->setVisible(false);
         }
         codeEditors[index]->setVisible(true);
+        // used so that codeDocumentTextInserted and codeDocumentTextDeleted know whether the parserLock
+        // is held by the message thread or not. We hold the lock in this function, but not when the
+        // code document is updated by the user editing text. Since both functions are called by the
+        // message thread, this is safe.
+        updatingDocumentsWithParserLock = true;
         if (index == 0) {
             codeEditors[index]->loadContent(audioProcessor.perspectiveEffect->getCode());
         } else {
             codeEditors[index]->loadContent(juce::MemoryInputStream(*audioProcessor.getFileBlock(originalIndex), false).readEntireStreamAsString());
         }
+        updatingDocumentsWithParserLock = false;
     }
     triggerAsyncUpdate();
 }
@@ -227,12 +233,22 @@ void OscirenderAudioProcessorEditor::editPerspectiveFunction(bool enable) {
 
 // parsersLock AND effectsLock must be locked before calling this function
 void OscirenderAudioProcessorEditor::codeDocumentTextInserted(const juce::String& newText, int insertIndex) {
+    if (updatingDocumentsWithParserLock) {
         updateCodeDocument();
+    } else {
+        juce::SpinLock::ScopedLockType parserLock(audioProcessor.parsersLock);
+        updateCodeDocument();
+    }
 }
 
 // parsersLock AND effectsLock must be locked before calling this function
 void OscirenderAudioProcessorEditor::codeDocumentTextDeleted(int startIndex, int endIndex) {
+    if (updatingDocumentsWithParserLock) {
         updateCodeDocument();
+    } else {
+        juce::SpinLock::ScopedLockType parserLock(audioProcessor.parsersLock);
+        updateCodeDocument();
+    }
 }
 
 // parsersLock AND effectsLock must be locked before calling this function

Source/PluginEditor.h

@@ -55,6 +55,8 @@ private:
     MainMenuBarModel menuBarModel{*this};
     juce::MenuBarComponent menuBar;
 
+    std::atomic<bool> updatingDocumentsWithParserLock = false;
+
 	void codeDocumentTextInserted(const juce::String& newText, int insertIndex) override;
 	void codeDocumentTextDeleted(int startIndex, int endIndex) override;
     void updateCodeDocument();

Source/PluginProcessor.cpp

@@ -381,10 +381,10 @@ void OscirenderAudioProcessor::changeCurrentFile(int index) {
 	if (index < 0 || index >= fileBlocks.size()) {
 		return;
 	}
-    changeSound(sounds[index]);
     currentFile = index;
     updateLuaValues();
     updateObjValues();
+    changeSound(sounds[index]);
 }
 
 void OscirenderAudioProcessor::changeSound(ShapeSound::Ptr sound) {

Source/lua/LuaParser.cpp

@@ -5,6 +5,7 @@
 LuaParser::LuaParser(juce::String script) {
     // initialization
     L = luaL_newstate();
+    lua_atpanic(L, panic);
     luaL_openlibs(L);
 
     this->script = script;
@@ -54,6 +55,7 @@ std::vector<float> LuaParser::run() {
     
 	lua_geti(L, LUA_REGISTRYINDEX, functionRef);
     
+    if (lua_isfunction(L, -1)) {
         const int ret = lua_pcall(L, 0, LUA_MULTRET, 0);
         if (ret != 0) {
             const char* error = lua_tostring(L, -1);
@@ -70,8 +72,13 @@ std::vector<float> LuaParser::run() {
                 values.push_back(value);
             }
         }
+    } else {
+        DBG("functionRef is not a function");
+        functionRef = -1;
+    }
 
-    lua_pop(L, 1);
+    // clear stack
+    lua_settop(L, 0);
 
 	step++;
     
@@ -86,3 +93,11 @@ void LuaParser::setVariable(juce::String variableName, double value) {
 	variables.push_back(value);
     updateVariables = true;
 }
+
+
+int LuaParser::panic(lua_State *L) {
+    const char *msg = lua_tostring(L, -1);
+    if (msg == NULL) msg = "error object is not a string";
+    DBG("PANIC: unprotected error in call to Lua API (%s)\n" << msg);
+    return 0;  /* return to Lua to abort */
+}

Source/lua/LuaParser.h

@@ -14,6 +14,8 @@ public:
 private:
 	void parse();
 
+	static int panic(lua_State* L);
+
 	int functionRef = -1;
 	long step = 1;
 	lua_State* L;