Fix assert on startup when calling back on an empty string

src/lua/core/Import.cpp

@@ -24,42 +24,42 @@
 #endif
 
 /**
-* We use Lua's require() functionality, but with a twist.
-*
-* When specifying a module name to `require()`, beginning the module name
-* with a separator (`.`) is syntactic sugar for prepending the source
-* directory of the calling file to the module name, forming a system of
-* relative name lookup.
-*
-* Relative name lookup cannot ascend levels in the filesystem, nor can it be
-* used to exit the virtual filesystem. It's merely a shorthand to implicitly
-* specify the module name of the calling file as a prefix to the module name
-* passed to `require()`. This is done as follows:
-*
-* -- when called from myname/modname/mod-load.lua
-* require '.module-A'
-* -- this call is transformed into:
-* require 'myname.modname.module-A'
-*
-* Once the full module name has been established, it is run through several
-* levels of lookup. First, the module name is tested against the import
-* cache, then against the list of modules registered by C++ code. Finally,
-* it is converted into a file path and tested against the filesystem to
-* load a lua file from disk.
-*
-* Filesystem lookup follows the usual rules; a file in a mod overrides files
-* earlier in the mod load order, and the overriden files cannot be loaded
-* from disk. If there is a C++ module with a specific name, it overrides all
-* Lua files with that name.
-*
-* The `package.core` object stores C++ modules for convenience. Access
-* is by standard Lua notation - `package.core.PiGui.Modules.ModelSpinner`
-* works just fine, as does `require 'PiGui.Modules.ModelSpinner'`.
-*
-* The `package.reimport(name)` function purges the cache for a specific
-* module name and repeats the loading process - useful for when a file
-* changes on disk as part of development.
-*/
+ * We use Lua's require() functionality, but with a twist.
+ *
+ * When specifying a module name to `require()`, beginning the module name
+ * with a separator (`.`) is syntactic sugar for prepending the source
+ * directory of the calling file to the module name, forming a system of
+ * relative name lookup.
+ *
+ * Relative name lookup cannot ascend levels in the filesystem, nor can it be
+ * used to exit the virtual filesystem. It's merely a shorthand to implicitly
+ * specify the module name of the calling file as a prefix to the module name
+ * passed to `require()`. This is done as follows:
+ *
+ * -- when called from myname/modname/mod-load.lua
+ * require '.module-A'
+ * -- this call is transformed into:
+ * require 'myname.modname.module-A'
+ *
+ * Once the full module name has been established, it is run through several
+ * levels of lookup. First, the module name is tested against the import
+ * cache, then against the list of modules registered by C++ code. Finally,
+ * it is converted into a file path and tested against the filesystem to
+ * load a lua file from disk.
+ *
+ * Filesystem lookup follows the usual rules; a file in a mod overrides files
+ * earlier in the mod load order, and the overriden files cannot be loaded
+ * from disk. If there is a C++ module with a specific name, it overrides all
+ * Lua files with that name.
+ *
+ * The `package.core` object stores C++ modules for convenience. Access
+ * is by standard Lua notation - `package.core.PiGui.Modules.ModelSpinner`
+ * works just fine, as does `require 'PiGui.Modules.ModelSpinner'`.
+ *
+ * The `package.reimport(name)` function purges the cache for a specific
+ * module name and repeats the loading process - useful for when a file
+ * changes on disk as part of development.
+ */
 
 // The cache table that stores file path -> module return value mappings
 static const char *IMPORT_CACHE_NAME = "Imports";
@@ -76,8 +76,8 @@ struct ImportInfo {
 };
 
 /**
-* Returns path of last element in the lua stack
-*/
+ * Returns path of last element in the lua stack
+ */
 static std::string get_caller(lua_State *L, int depth = 1)
 {
  // XXX: Extraneous copy
@@ -114,13 +114,13 @@ static std::string get_caller(lua_State *L, int depth = 1)
 }
 
 /**
-* Generate a lua module name from a given input path.
-* If the path contains a directory component containing a separator (period)
-* this function will return an empty string, as lua module names cannot contain
-* a non-separating period.
-* This function discards the trailing component of the directory path. If you
-* wish to retain it, ensure the path string ends with '/'.
-*/
+ * Generate a lua module name from a given input path.
+ * If the path contains a directory component containing a separator (period)
+ * this function will return an empty string, as lua module names cannot contain
+ * a non-separating period.
+ * This function discards the trailing component of the directory path. If you
+ * wish to retain it, ensure the path string ends with '/'.
+ */
 static std::string path_to_module(std::string path)
 {
  std::string module_name;
@@ -146,7 +146,7 @@ static std::string path_to_module(std::string path)
  end = path.find_first_of('/', start);
  }
 
- if (module_name.back() == '.')
+ if (!module_name.empty() && module_name.back() == '.')
  module_name.pop_back();
 
  return module_name;