Cleanup loading of translations.

The new code clearly distinguishes between loading default
translations from the "base" theme and loading (additional)
translations from the (inherited) themes.

Also the former method put the directories onto sys.path and imported
the translation files as modules. This not only keeps the whole module
in memory (which might be neglectable nowadays) but also requires
extra code to reload the module for each theme.  The new method loads
the file and executes it using exec().

As a side-effect, this also fixed the bug that translations provided
by the "base" theme got lost if another theme provided additional
message strings.

Author: htgoebel

nikola/utils.py

@@ -45,6 +45,7 @@
 from collections import defaultdict, OrderedDict
 from html import unescape as html_unescape
 from importlib import reload as _reload
+from pathlib import Path
 from unicodedata import normalize as unicodenormalize
 from urllib.parse import quote as urlquote
 from urllib.parse import unquote as urlunquote
@@ -710,41 +711,48 @@ def load_messages(themes, translations, default_lang, themes_dirs):
     and "younger" themes have priority.
     """
     messages = Functionary(dict, default_lang)
-    oldpath = list(sys.path)
-    found = {lang: False for lang in translations.keys()}
+    found = {lang: False for lang in translations}
+    completion_status = found.copy()
     last_exception = None
-    completion_status = {lang: False for lang in translations.keys()}
+
+    def load_msgs(lang, folder):
+        globals = {}
+        msg_file = folder / f'messages_{lang}.py'
+        try:
+            pysrc = msg_file.read_bytes()
+            exec(pysrc, globals)
+        except Exception as ex:
+            last_exception = ex   # noqa: F841
+        return globals.get('MESSAGES', {})
+
+    # load default translations provided by "base" theme
+    default_folder = Path(get_theme_path_real('base', themes_dirs)) / 'messages'
+    english = load_msgs('en', default_folder)
+    for lang in translations:
+        messages[lang].update(english)
+        messages[lang].update(load_msgs(lang, default_folder))
+
+    # load translations for each theme
     for theme_name in themes[::-1]:
-        msg_folder = os.path.join(get_theme_path(theme_name), 'messages')
-        default_folder = os.path.join(get_theme_path_real('base', themes_dirs), 'messages')
-        sys.path.insert(0, default_folder)
-        sys.path.insert(0, msg_folder)
-
-        english = __import__('messages_en')
-        # If we don't do the reload, the module is cached
-        _reload(english)
-        for lang in translations.keys():
-            try:
-                translation = __import__('messages_' + lang)
-                # If we don't do the reload, the module is cached
-                _reload(translation)
-                found[lang] = True
-                if sorted(translation.MESSAGES.keys()) != sorted(english.MESSAGES.keys()):
-                    completion_status[lang] = completion_status[lang] or False
-                else:
-                    completion_status[lang] = True
-
-                messages[lang].update(english.MESSAGES)
-                for k, v in translation.MESSAGES.items():
-                    if v:
-                        messages[lang][k] = v
-                del translation
-            except ImportError as orig:
-                last_exception = orig
-        del english
-        sys.path = oldpath
+        msg_folder = Path(get_theme_path(theme_name)) / 'messages'
+        # load English default from this theme
+        english = load_msgs('en', msg_folder)
+        messages[lang].update(english)  # FIXME: This will overwrite translated strings
+        for lang in translations:
+            translation = load_msgs(lang, msg_folder)
+            if not translation:
+                continue
+            found[lang] = True
+            for k, v in translation.items():
+                if v:
+                    messages[lang][k] = v
+            if set(translation) != set(english):
+                completion_status[lang] = completion_status[lang] or False
+            else:
+                completion_status[lang] = True
 
     if not all(found.values()):
+        print(lang, last_exception)
         raise LanguageNotFoundError(lang, last_exception)
     for lang, status in completion_status.items():
         if not status and lang not in INCOMPLETE_LANGUAGES_WARNED: