searxng/searx/plugins/autodetect_search_language.py
Markus Heiser ed901ab18e [mod] improve 'Autodetect search language' plugin
- Add documentation to the plugin
- Harmonize FastText language model with SearXNG's language model

Reosurces::

    import fasttext                                    # --> +10 MB
    fasttext.load_model(str(data_dir / 'lid.176.ftz')) # --> +4MB

Suggested-by: @dalf

- To speed up and simplify the deployment use fasttext-wheel instead of fasttext
- Building numpy on the Alpine Linux of docker-images takes ages --> install
  py3-numpy from Alpines package manager (apk)
- Alpine Linux on docker-images (musl libc) do not support fasttext-wheel (gnu
  libc) --> patch Dockerfile and build from fastetxt:

     sed -i s/fasttext-wheel/fasttext/ requirements.txt

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
2022-12-11 11:26:07 +01:00

116 lines
4.7 KiB
Python

# SPDX-License-Identifier: AGPL-3.0-or-later
# lint: pylint
"""Plugin to detect the search language from the search query.
The language detection is done by using the fastText_ library (`python
fasttext`_). fastText_ distributes the `language identification model`_, for
reference:
- `FastText.zip: Compressing text classification models`_
- `Bag of Tricks for Efficient Text Classification`_
The `language identification model`_ support the language codes (ISO-639-3)::
af als am an ar arz as ast av az azb ba bar bcl be bg bh bn bo bpy br bs bxr
ca cbk ce ceb ckb co cs cv cy da de diq dsb dty dv el eml en eo es et eu fa
fi fr frr fy ga gd gl gn gom gu gv he hi hif hr hsb ht hu hy ia id ie ilo io
is it ja jbo jv ka kk km kn ko krc ku kv kw ky la lb lez li lmo lo lrc lt lv
mai mg mhr min mk ml mn mr mrj ms mt mwl my myv mzn nah nap nds ne new nl nn
no oc or os pa pam pfl pl pms pnb ps pt qu rm ro ru rue sa sah sc scn sco sd
sh si sk sl so sq sr su sv sw ta te tg th tk tl tr tt tyv ug uk ur uz vec vep
vi vls vo wa war wuu xal xmf yi yo yue zh
The `language identification model`_ is harmonized with the SearXNG's language
(locale) model. General conditions of SearXNG's locale model are:
a. SearXNG's locale of a query is passed to the
:py:obj:`searx.locales.get_engine_locale` to get a language and/or region
code that is used by an engine.
b. SearXNG and most of the engines do not support all the languages from
language model and there might be also a discrepancy in the ISO-639-3 and
ISO-639-2 handling (:py:obj:`searx.locales.get_engine_locale`). Further
more, in SearXNG the locales like ``zh-TH`` (``zh-CN``) are mapped to
``zh_Hant`` (``zh_Hans``).
Conclusion: This plugin does only auto-detect the languages a user can select in
the language menu (:py:obj:`supported_langs`).
SearXNG's locale of a query comes from (*highest wins*):
1. The ``Accept-Language`` header from user's HTTP client.
2. The user select a locale in the preferences.
3. The user select a locale from the menu in the query form (e.g. ``:zh-TW``)
4. This plugin is activated in the preferences and the locale (only the language
code / none region code) comes from the fastText's language detection.
Conclusion: There is a conflict between the language selected by the user and
the language from language detection of this plugin. For example, the user
explicitly selects the German locale via the search syntax to search for a term
that is identified as an English term (try ``:de-DE thermomix``, for example).
.. hint::
To SearXNG maintainers; please take into account: under some circumstances
the auto-detection of the language of this plugin could be detrimental to
users expectations. Its not recommended to activate this plugin by
default. It should always be the user's decision whether to activate this
plugin or not.
.. _fastText: https://fasttext.cc/
.. _python fasttext: https://pypi.org/project/fasttext/
.. _language identification model: https://fasttext.cc/docs/en/language-identification.html
.. _Bag of Tricks for Efficient Text Classification: https://arxiv.org/abs/1607.01759
.. _`FastText.zip: Compressing text classification models`: https://arxiv.org/abs/1612.03651
"""
from flask_babel import gettext
import fasttext
import babel
from searx.data import data_dir
from searx.languages import language_codes
# Monkey patch: prevent fasttext from showing a (useless) warning when loading a
# model.
fasttext.FastText.eprint = lambda x: None
name = gettext('Autodetect search language')
description = gettext('Automatically detect the query search language and switch to it.')
preference_section = 'general'
default_on = False
lang_model: fasttext.FastText._FastText = None
"""fasttext model to predict laguage of a search term"""
supported_langs = set()
"""Languages supported by most searxng engines (:py:obj:`searx.languages.language_codes`)."""
def get_model():
# lazy load, in order to to save memory
global lang_model # pylint: disable=global-statement
if lang_model is None:
lang_model = fasttext.load_model(str(data_dir / 'lid.176.ftz'))
return lang_model
def pre_search(request, search): # pylint: disable=unused-argument
prediction = get_model().predict(search.search_query.query, k=1, threshold=0.3)
if prediction:
lang = prediction[0][0].split('__label__')[1]
if lang in supported_langs:
search.search_query.lang = lang
try:
search.search_query.locale = babel.Locale.parse(lang)
except babel.core.UnknownLocaleError:
pass
return True
def init(app, settings): # pylint: disable=unused-argument
for searxng_locale in language_codes:
supported_langs.add(searxng_locale[0].split('-')[0])
return True