fixes

src/engine/EnginePaths.cpp

@@ -173,7 +173,7 @@ std::string EnginePaths::createMemoryDevice() {
     auto device = std::make_unique<io::MemoryDevice>();
         std::string name;
     do {
-        name = std::string("M.") + generate_random_base64<6>();
+        name = std::string("W.") + generate_random_base64<6>();
     } while (std::find(mounted.begin(), mounted.end(), name) != mounted.end());
     
     io::set_device(name, std::move(device));

src/io/devices/MemoryDevice.cpp

@@ -59,10 +59,16 @@ io::file_time_type io::MemoryDevice::lastWriteTime(std::string_view path) {
 }
 
 bool io::MemoryDevice::exists(std::string_view path) {
+    if (path.empty()) {
+        return true;
+    }
     return nodes.find(std::string(path)) != nodes.end();
 }
 
 bool io::MemoryDevice::isdir(std::string_view path) {
+    if (path.empty()) {
+        return true;
+    }
     const auto& found = nodes.find(std::string(path));
     if (found == nodes.end()) {
         return false;
@@ -201,6 +207,9 @@ io::MemoryDevice::Node* io::MemoryDevice::createFile(
 }
 
 io::MemoryDevice::Dir* io::MemoryDevice::getDir(std::string_view path) {
+    if (path.empty()) {
+        return &rootDir;
+    }
     const auto& found = nodes.find(std::string(path));
     if (found == nodes.end()) {
         return nullptr;

src/io/devices/MemoryDevice.hpp

@@ -62,6 +62,7 @@ namespace io {
         std::unique_ptr<PathsGenerator> list(std::string_view path) override;
     private:
         std::unordered_map<std::string, Node> nodes;
+        Dir rootDir {};
 
         Node* createFile(std::string path, util::Buffer<char>&& content);
         Dir* createDir(std::string path);

src/logic/scripting/lua/libs/libapp.cpp

@@ -4,12 +4,16 @@
 #include "io/devices/MemoryDevice.hpp"
 
 static int l_create_memory_device(lua::State* L) {
-    auto name = lua::require_string(L, 1);
+    std::string name = lua::require_string(L, 1);
     if (io::get_device(name)) {
         throw std::runtime_error(
-            "entry-point '" + std::string(name) + "' is already used"
+            "entry-point '" + name + "' is already used"
         );
     }
+    if (name.find(':') != std::string::npos) {
+        throw std::runtime_error("invalid entry point name");
+    }
+    
     io::set_device(name, std::make_unique<io::MemoryDevice>());
     return 0;
 }

src/logic/scripting/lua/libs/libfile.cpp

@@ -5,6 +5,7 @@
 #include "engine/Engine.hpp"
 #include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
+#include "io/devices/MemoryDevice.hpp"
 #include "io/devices/ZipFileDevice.hpp"
 #include "util/stringutil.hpp"
 #include "api_lua.hpp"
@@ -49,6 +50,14 @@ static bool is_writeable(const std::string& entryPoint) {
     if (entryPoint.substr(0, 2) == "W.") {
         return true;
     }
+    // todo: do better
+    auto device = io::get_device(entryPoint);
+    if (device == nullptr) {
+        return false;
+    }
+    if (dynamic_cast<io::MemoryDevice*>(device.get())) {
+        return true;
+    }
     if (writeable_entry_points.find(entryPoint) != writeable_entry_points.end()) {
         return true;
     }