[WIP] check usable languages

securedrop/i18n.py

@@ -29,8 +29,7 @@
 from flask import Flask, g, request, session
 from flask_babel import Babel
 
-from sdconfig import SDConfig
-
+from sdconfig import SDConfig, FALLBACK_LOCALE
 
 class RequestLocaleInfo:
     """
@@ -128,28 +127,30 @@ def configure_babel(config: SDConfig, app: Flask) -> Babel:
 
 def validate_locale_configuration(config: SDConfig, babel: Babel) -> None:
     """
-    Ensure that the configured locales are valid and translated.
+    Check that configured locales are available in the filesystem and therefore usable by
+    Babel.  Warn about configured locales that are not usable, unless we're left with
+    no usable default or fallback locale, in which case raise an exception.
     """
-    if config.DEFAULT_LOCALE not in config.SUPPORTED_LOCALES:
-        raise ValueError(
-            'The default locale "{}" is not included in the set of supported locales "{}"'.format(
-                config.DEFAULT_LOCALE, config.SUPPORTED_LOCALES
-            )
-        )
-
-    translations = babel.list_translations()
-    for locale in config.SUPPORTED_LOCALES:
-        if locale == "en_US":
-            continue
-
+    available = set(babel.list_translations())  # available in the filesystem
+    available.add(FALLBACK_LOCALE)
+    configured = set(config.SUPPORTED_LOCALES)  # configured by the administrator
+    usable = available & configured  # usable by Babel
+
+    # This loop could be replaced with a set operation, but we'd have to iterate over the result
+    # anyway in order to log it.
+    for locale in configured:
         parsed = Locale.parse(locale)
-        if parsed not in translations:
-            raise ValueError(
-                'Configured locale "{}" is not in the set of translated locales "{}"'.format(
-                    parsed, translations
-                )
+        if parsed not in usable:
+            babel.app.logger.error(
+                f'Configured locale "{parsed}" is not in the set of usable locales {usable}'
             )
 
+    defaults = set([config.DEFAULT_LOCALE, FALLBACK_LOCALE]) & usable
+    if len(defaults) == 0:
+        raise ValueError(
+            f'None of the default locales {defaults} is in the set of usable locales {usable}'
+        )
+
 
 LOCALES = collections.OrderedDict()  # type: collections.OrderedDict[str, RequestLocaleInfo]
 

securedrop/sdconfig.py

@@ -8,6 +8,9 @@
 from typing import Set
 
 
+FALLBACK_LOCALE = "en_US"
+
+
 class SDConfig:
     def __init__(self) -> None:
         try:
@@ -120,7 +123,7 @@ def __init__(self) -> None:
         # Config entries used by i18n.py
         # Use en_US as the default locale if the key is not defined in _config
         self.DEFAULT_LOCALE = getattr(
-            _config, "DEFAULT_LOCALE", "en_US"
+            _config, "DEFAULT_LOCALE", FALLBACK_LOCALE,
         )  # type: str
         supported_locales = set(getattr(
             _config, "SUPPORTED_LOCALES", [self.DEFAULT_LOCALE]

securedrop/tests/test_i18n.py

@@ -225,11 +225,43 @@ def test_i18n(journalist_app, config):
         verify_i18n(app)
 
 
-def test_supported_locales(config):
+def test_no_usable_default_locale(config):
+    '''
+    The apps fail if neither the default nor the fallback locale is usable.
+    '''
     fake_config = SDConfig()
+    fake_config.DEFAULT_LOCALE = 'eo'  # Esperanto
+    fake_config.SUPPORTED_LOCALES = ['eo']
+    fake_config.TRANSLATION_DIRS = Path(config.TEMP_DIR)
+
+    with pytest.raises(ValueError, match='in the set of usable locales'):
+        journalist_app_module.create_app(fake_config)
+
+    with pytest.raises(ValueError, match='in the set of usable locales'):
+        source_app.create_app(fake_config)
+
+
+def test_unusable_default_but_usable_fallback_locale(config, caplog):
+    '''
+    The apps start even if the default locale is unusable, as along as the fallback locale is
+    usable, but log an error for OSSEC to pick up.
+    '''
+    fake_config = SDConfig()
+    fake_config.DEFAULT_LOCALE = 'eo'  # Esperanto
+    fake_config.SUPPORTED_LOCALES = ['eo', 'en_US']
+    fake_config.TRANSLATION_DIRS = Path(config.TEMP_DIR)
+
+    for app in (journalist_app_module.create_app(fake_config),
+                source_app.create_app(fake_config)):
+        with app.app_context():
+            assert 'Configured locale "eo" is not in the set of usable locales' in caplog.text
+
 
-    # Check that an invalid locale raises an error during app
-    # configuration.
+def test_invalid_locales(config):
+    '''
+    An invalid locale raises an error during app configuration.
+    '''
+    fake_config = SDConfig()
     fake_config.SUPPORTED_LOCALES = ['en_US', 'yy_ZZ']
     fake_config.TRANSLATION_DIRS = Path(config.TEMP_DIR)
 
@@ -239,16 +271,21 @@ def test_supported_locales(config):
     with pytest.raises(UnknownLocaleError):
         source_app.create_app(fake_config)
 
-    # Check that a valid but unsupported locale raises an error during
-    # app configuration.
+
+def test_valid_but_unusable_locales(config, caplog):
+    '''
+    The apps start with one or more unusable, but still valid, locales, but log an error for
+    OSSEC to pick up.
+    '''
+    fake_config = SDConfig()
+
     fake_config.SUPPORTED_LOCALES = ['en_US', 'wae_CH']
     fake_config.TRANSLATION_DIRS = Path(config.TEMP_DIR)
 
-    with pytest.raises(ValueError, match="not in the set of translated locales"):
-        journalist_app_module.create_app(fake_config)
-
-    with pytest.raises(ValueError, match="not in the set of translated locales"):
-        source_app.create_app(fake_config)
+    for app in (journalist_app_module.create_app(fake_config),
+                source_app.create_app(fake_config)):
+        with app.app_context():
+            assert 'Configured locale "wae_CH" is not in the set of usable locales' in caplog.text
 
 
 def test_language_tags():