config.load_langs_on_demand: permits on-the-fly loading/unloading, to facilitate proc-gen use cases

lingua_franca/__init__.py

@@ -2,3 +2,5 @@
     get_active_langs, _set_active_langs, get_primary_lang_code, \
     get_full_lang_code, resolve_resource_file, load_language, \
     load_languages, unload_language, unload_languages, get_supported_langs
+
+from lingua_franca import config

lingua_franca/config.py

@@ -0,0 +1 @@
+load_langs_on_demand = False

lingua_franca/internal.py

@@ -5,6 +5,8 @@
 from sys import version
 from warnings import warn
 
+from lingua_franca import config
+
 _SUPPORTED_LANGUAGES = ("cs", "da", "de", "en", "es", "fr", "hu",
                         "it", "nl", "pl", "pt", "sv")
 
@@ -457,16 +459,14 @@ def is_error_type(_type):
     def localized_function_decorator(func):
         # Wrapper's logic
         def _call_localized_function(func, *args, **kwargs):
+            lang_code = None
+            load_langs_on_demand = config.load_langs_on_demand
+            unload_language_afterward = False
             func_signature = signature(func)
             func_params = list(func_signature.parameters)
             lang_param_index = func_params.index('lang')
             full_lang_code = None
 
-            # Momentarily assume we're not passing a lang code
-            lang_code = get_default_lang()
-            if not lang_code:
-                raise NoSuchModuleError("No language module loaded.")
-
             # Check if we're passing a lang as a kwarg
             if 'lang' in kwargs.keys():
                 lang_param = kwargs['lang']
@@ -487,6 +487,15 @@ def _call_localized_function(func, *args, **kwargs):
                     lang_code = args[lang_param_index]
                 args = args[:lang_param_index] + args[lang_param_index+1:]
 
+            # Turns out, we aren't passing a lang code at all
+            lang_code = lang_code or get_default_lang()
+            if not lang_code:
+                if load_langs_on_demand:
+                    raise NoSuchModuleError("No language module loaded "
+                                            "and none specified.")
+                else:
+                    raise NoSuchModuleError("No language module loaded.")
+
             if lang_code not in _SUPPORTED_LANGUAGES:
                 try:
                     tmp = lang_code
@@ -528,9 +537,14 @@ def _call_localized_function(func, *args, **kwargs):
                 raise NoSuchModuleError("Module lingua_franca." +
                                         _module_name + " not recognized")
             if lang_code not in _localized_functions[_module_name].keys():
-                raise NoSuchModuleError(_module_name + " module of language '" +
-                                        lang_code + "' is not currently loaded.")
-
+                if load_langs_on_demand:
+                    load_language(lang_code)
+                    unload_language_afterward = True
+                else:
+                    raise NoSuchModuleError(_module_name +
+                                            " module of language '" +
+                                            lang_code +
+                                            "' is not currently loaded.")
             func_name = func.__name__.split('.')[-1]
             # At some point in the past, both the module and the language
             # were imported/loaded, respectively.
@@ -573,6 +587,8 @@ def _call_localized_function(func, *args, **kwargs):
             # Unload all the stuff we just assembled and imported
             del localized_func
             del _module
+            if unload_language_afterward:
+                unload_language(lang_code)
             return r_val
 
         # Actual wrapper