[mod] set 'engine.supported_languages' from the origin python module

The key of the dictionary 'searx.data.ENGINES_LANGUAGES' is the *engine name*
configured in settings.xml.  When multiple engines are configured to use the
same origin engine (e.g. `engine: google`)::

    - name: google
      engine: google
      use_mobile_ui: false
      ...

    - name: google italian
      engine: google
      use_mobile_ui: false
      language: it
      ...

    - name: google mobile ui
      engine: google
      shortcut: gomui
      use_mobile_ui: true

There exists no entry for ENGINES_LANGUAGES[engine.name] (e.g. `name: google
mobile ui` or `name: google italian`).  This issue can be solved by recreate the
ENGINES_LANGUAGES::

    make data.languages

But this is nothing an SearXNG admin would like to do when just configuring
additional engines, since this just doubles entries in ENGINES_LANGUAGES and
BTW: `make data.languages` has various external requirements which might be not
installed or not available, on a production host.

With this patch, if engine.name fails, ENGINES_LANGUAGES[engine.engine] is used
to get the engine.supported_languages (e.g. `google` for the engine named
`google mobile`).

For an engine, when there is `language: ...` in the YAML settings, the engine
supports only one language, in this case engine.supported_languages should
contains this value defined in settings.yml (e.g. `it` for the engine named
`google italian`).

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Closes: https://github.com/searxng/searxng/issues/384

searx/engines/__init__.py

@@ -137,7 +137,7 @@ def update_engine_attributes(engine, engine_data):
             if isinstance(param_value, str):
                 param_value = list(map(str.strip, param_value.split(',')))
             engine.categories = param_value
-        elif param_name != 'engine':
+        else:
             setattr(engine, param_name, param_value)
 
     # set default attributes
@@ -147,11 +147,35 @@ def update_engine_attributes(engine, engine_data):
 
 
 def set_language_attributes(engine):
-    # pylint: disable=protected-access
     # assign supported languages from json file
     if engine.name in ENGINES_LANGUAGES:
         engine.supported_languages = ENGINES_LANGUAGES[engine.name]
 
+    elif engine.engine in ENGINES_LANGUAGES:
+        # The key of the dictionary ENGINES_LANGUAGES is the *engine name*
+        # configured in settings.xml.  When multiple engines are configured in
+        # settings.yml to use the same origin engine (python module) these
+        # additional engines can use the languages from the origin engine.
+        # For this use the configured ``engine: ...`` from settings.yml
+        engine.supported_languages = ENGINES_LANGUAGES[engine.engine]
+
+    if hasattr(engine, 'language'):
+        # For an engine, when there is `language: ...` in the YAML settings, the
+        # engine supports only one language, in this case
+        # engine.supported_languages should contains this value defined in
+        # settings.yml
+        if engine.language not in engine.supported_languages:
+            raise ValueError(
+                "settings.yml - engine: '%s' / language: '%s' not supported" % (
+                    engine.name, engine.language ))
+
+        if isinstance(engine.supported_languages, dict):
+            engine.supported_languages = {
+                engine.language : engine.supported_languages[engine.language]
+            }
+        else:
+            engine.supported_languages = [engine.language]
+
     # find custom aliases for non standard language codes
     for engine_lang in engine.supported_languages:
         iso_lang = match_language(engine_lang, BABEL_LANGS, fallback=None)
@@ -172,6 +196,7 @@ def set_language_attributes(engine):
             'Accept-Language': 'ja-JP,ja;q=0.8,en-US;q=0.5,en;q=0.3',  # bing needs a non-English language
         }
         engine.fetch_supported_languages = (
+            # pylint: disable=protected-access
             lambda: engine._fetch_supported_languages(
                 get(engine.supported_languages_url, headers=headers))
         )

searx/settings.yml

@@ -601,6 +601,17 @@ engines:
     # additional_tests:
     #   android: *test_android
 
+  # - name: google italian
+  #   engine: google
+  #   shortcut: goit
+  #   use_mobile_ui: false
+  #   language: it
+
+  # - name: google mobile ui
+  #   engine: google
+  #   shortcut: gomui
+  #   use_mobile_ui: true
+
   - name: google images
     engine: google_images
     shortcut: goi