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[mod] add locale.get_engine_locale to get predictable results
The match_language function sometimes returns incorrect results which is why a new function get_engine_locale is required. A bugfix of the match_language is not easily possible, because there is almost no documentation for it and already the call parameters are undefined. E.g. the function processes values like the ones from yahoo:: "yahoo": [ "ar", ... "zh_chs", "zh_cht" ] The get_engine_locale has been documented in detail, there is a clear description of the assumptions as well as the requirements and approximation rules (read doc-string for more details):: Argument ``engine_locales`` is a python dict that maps *SearXNG locales* to corresponding *engine locales*: <engine>: { # SearXNG string : engine-string 'ca-ES' : 'ca_ES', 'fr-BE' : 'fr_BE', 'fr-CA' : 'fr_CA', 'fr-CH' : 'fr_CH', 'fr' : 'fr_FR', ... 'pl-PL' : 'pl_PL', 'pt-PT' : 'pt_PT' } .. hint:: The *SearXNG locale* string has to be known by babel! In the following you will find a comparison: >>> import babel.languages >>> from searx.utils import match_language >>> from searx.locales import get_engine_locale Assume we have an engine that supports the follwoing locales: >>> lang_list = { ... "zh-CN": "zh_CN", ... "zh-HK": "zh_HK", ... "nl-BE": "nl_BE", ... "fr-CA": "fr_CA", ... } Assumption: A. When a user selects a language the results should be optimized according to the selected language. B. When user selects a language and a territory the results should be optimized with first priority on territory and second on language. ---- Example: (Assumption A.) A user selects region 'zh-TW' which should end in zh_HK hint: CN is 'Hans' and HK ('Hant') fits better to TW ('Hant') >>> get_engine_locale('zh-TW', lang_list) 'zh_HK' >>> lang_list[match_language('zh-TW', lang_list)] 'zh_CN' ---- Example: (Assumption A.) A user selects only the language 'zh' which should end in CN >>> get_engine_locale('zh', lang_list) 'zh_CN' >>> lang_list[match_language('zh', lang_list)] 'zh_CN' ---- Example: (Assumption B.) A user selects region 'fr-BE' which should end in nl-BE hint: priority should be on the territory the user selected. If the user prefers 'fr' he will select 'fr' without a region tag. >>> get_engine_locale('fr-BE', lang_list, default='unknown') 'nl_BE' >>> match_language('fr-BE', lang_list, fallback='unknown') 'fr-CA' ---- Example: (Assumption A.) A user selects only the language 'fr' which should end in fr_CA >>> get_engine_locale('fr', lang_list) 'fr_CA' >>> lang_list[match_language('fr', lang_list)] 'fr_CA' ---- The difference in priority on the territory is best shown with a engine that supports the following locales: >>> lang_list = { ... "fr-FR": "fr_FR", ... "fr-CA": "fr_CA", ... "en-GB": "en_GB", ... "nl-BE": "nl_BE", ... } ---- Example: (Assumption A.) A user selects only a language >>> get_engine_locale('en', lang_list) 'en_GB' >>> match_language('en', lang_list) 'en-GB' hint: the engine supports fr_FR and fr_CA since no territory is given, fr_FR takes priority .. >>> get_engine_locale('fr', lang_list) 'fr_FR' >>> lang_list[match_language('fr', lang_list)] 'fr_FR' ---- Example: (Assumption B.) A user selects region 'fr-BE' which should end in nl-BE >>> get_engine_locale('fr-BE', lang_list) 'nl_BE' >>> lang_list[match_language('fr-BE', lang_list)] 'fr_FR' ---- If the user selects a language and there are two locales like the following: >>> lang_list = { ... "fr-BE": "fr_BE", ... "fr-CH": "fr_CH", ... } >>> >>> get_engine_locale('fr', lang_list) 'fr_BE' >>> lang_list[match_language('fr', lang_list)] 'fr_BE' Looks like both functions return the same value, but match_language depends on the order of the dictionary (which is not predictable): >>> lang_list = { ... "fr-CH": "fr_CH", ... "fr-BE": "fr_BE", ... } >>> get_engine_locale('fr', lang_list) 'fr_BE' >>> lang_list[match_language('fr', lang_list)] 'fr_CH' >>> The get_engine_locale selects the locale by looking at the "population percent" and this percentage has an higher amount in BE (68.%) compared to CH (21%) Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
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searx/locales.py
137
searx/locales.py
@ -10,6 +10,8 @@ import pathlib
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from babel import Locale
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from babel.support import Translations
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import babel.languages
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import babel.core
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import flask_babel
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import flask
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from flask.ctx import has_request_context
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@ -150,3 +152,138 @@ def locales_initialize(directory=None):
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LOCALE_NAMES[tag] = get_locale_descr(locale, dirname)
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if locale.text_direction == 'rtl':
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RTL_LOCALES.add(tag)
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def get_engine_locale(searxng_locale, engine_locales, default=None):
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"""Return engine's language (aka locale) string that best fits to argument
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``searxng_locale``.
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Argument ``engine_locales`` is a python dict that maps *SearXNG locales* to
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corresponding *engine locales*:
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<engine>: {
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# SearXNG string : engine-string
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'ca-ES' : 'ca_ES',
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'fr-BE' : 'fr_BE',
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'fr-CA' : 'fr_CA',
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'fr-CH' : 'fr_CH',
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'fr' : 'fr_FR',
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...
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'pl-PL' : 'pl_PL',
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'pt-PT' : 'pt_PT'
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}
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.. hint::
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The *SearXNG locale* string has to be known by babel!
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If there is no direct 1:1 mapping, this functions tries to narrow down
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engine's language (locale). If no value can be determined by these
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approximation attempts the ``default`` value is returned.
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Assumptions:
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A. When user select a language the results should be optimized according to
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the selected language.
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B. When user select a language and a territory the results should be
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optimized with first priority on terrirtory and second on language.
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First approximation rule (*by territory*):
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When the user selects a locale with terrirtory (and a language), the
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territory has priority over the language. If any of the offical languages
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in the terrirtory is supported by the engine (``engine_locales``) it will
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be used.
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Second approximation rule (*by language*):
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If "First approximation rule" brings no result or the user selects only a
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language without a terrirtory. Check in which territories the language
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has an offical status and if one of these territories is supported by the
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engine.
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"""
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# pylint: disable=too-many-branches
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engine_locale = engine_locales.get(searxng_locale)
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if engine_locale is not None:
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# There was a 1:1 mapping (e.g. "fr-BE --> fr_BE" or "fr --> fr_FR"), no
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# need to narrow language nor territory.
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return engine_locale
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locale = babel.Locale.parse(searxng_locale, sep='-')
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# SearXNG's selected locale is not supported by the engine ..
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if locale.territory:
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# Try to narrow by *offical* languages in the territory (??-XX).
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for official_language in babel.languages.get_official_languages(locale.territory, de_facto=True):
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searxng_locale = official_language + '-' + locale.territory
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engine_locale = engine_locales.get(searxng_locale)
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if engine_locale is not None:
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return engine_locale
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# Engine does not support one of the offical languages in the territory or
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# there is only a language selected without a territory.
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# Now lets have a look if the searxng_lang (the language selected by the
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# user) is a offical language in other territories. If so, check if
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# engine does support the searxng_lang in this other territory.
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if locale.language:
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searxng_lang = locale.language
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if locale.script:
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searxng_lang += '_' + locale.script
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terr_lang_dict = {}
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for territory, langs in babel.core.get_global("territory_languages").items():
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if not langs.get(searxng_lang, {}).get('official_status'):
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continue
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terr_lang_dict[territory] = langs.get(searxng_lang)
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# first: check fr-FR, de-DE .. is supported by the engine
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territory = locale.language.upper()
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if terr_lang_dict.get(territory):
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searxng_locale = locale.language + '-' + territory
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engine_locale = engine_locales.get(searxng_locale)
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if engine_locale is not None:
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return engine_locale
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# second: sort by population_percent and take first match
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# drawback of "population percent": if there is a terrirtory with a
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# small number of people (e.g 100) but the majority speaks the
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# language, then the percentage migth be 100% (--> 100 people) but in
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# a different terrirtory with more people (e.g. 10.000) where only 10%
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# speak the language the total amount of speaker is higher (--> 200
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# people).
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#
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# By example: The population of Saint-Martin is 33.000, of which 100%
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# speak French, but this is less than the 30% of the approximately 2.5
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# million Belgian citizens
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#
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# - 'fr-MF', 'population_percent': 100.0, 'official_status': 'official'
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# - 'fr-BE', 'population_percent': 38.0, 'official_status': 'official'
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terr_lang_list = []
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for k, v in terr_lang_dict.items():
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terr_lang_list.append((k, v))
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for territory, _lang in sorted(terr_lang_list, key=lambda item: item[1]['population_percent'], reverse=True):
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searxng_locale = locale.language + '-' + territory
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engine_locale = engine_locales.get(searxng_locale)
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if engine_locale is not None:
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return engine_locale
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# No luck: narrow by "language from territory" and "territory from language"
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# does not fit to a locale supported by the engine.
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if engine_locale is None:
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engine_locale = default
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return default
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