[mod] Google: reversed engineered & upgrade to data_type: traits_v1

Partial reverse engineering of the Google engines including a improved language
and region handling based on the engine.traits_v1 data.

When ever possible the implementations of the Google engines try to make use of
the async REST APIs.  The get_lang_info() has been generalized to a
get_google_info() function / especially the region handling has been improved by
adding the cr parameter.

searx/data/engine_traits.json
  Add data type "traits_v1" generated by the fetch_traits() functions from:

  - Google (WEB),
  - Google images,
  - Google news,
  - Google scholar and
  - Google videos

  and remove data from obsolete data type "supported_languages".

  A traits.custom type that maps region codes to *supported_domains* is fetched
  from https://www.google.com/supported_domains

searx/autocomplete.py:
  Reversed engineered autocomplete from Google WEB.  Supports Google's languages and
  subdomains.  The old API suggestqueries.google.com/complete has been replaced
  by the async REST API: https://{subdomain}/complete/search?{args}

searx/engines/google.py
  Reverse engineering and extensive testing ..
  - fetch_traits():  Fetch languages & regions from Google properties.
  - always use the async REST API (formally known as 'use_mobile_ui')
  - use *supported_domains* from traits
  - improved the result list by fetching './/div[@data-content-feature]'
    and parsing the type of the various *content features* --> thumbnails are
    added

searx/engines/google_images.py
  Reverse engineering and extensive testing ..
  - fetch_traits():  Fetch languages & regions from Google properties.
  - use *supported_domains* from traits
  - if exists, freshness_date is added to the result
  - issue 1864: result list has been improved a lot (due to the new cr parameter)

searx/engines/google_news.py
  Reverse engineering and extensive testing ..
  - fetch_traits():  Fetch languages & regions from Google properties.
    *supported_domains* is not needed but a ceid list has been added.
  - different region handling compared to Google WEB
  - fixed for various languages & regions (due to the new ceid parameter) /
    avoid CONSENT page
  - Google News do no longer support time range
  - result list has been fixed: XPath of pub_date and pub_origin

searx/engines/google_videos.py
  - fetch_traits():  Fetch languages & regions from Google properties.
  - use *supported_domains* from traits
  - add paging support
  - implement a async request ('asearch': 'arc' & 'async':
    'use_ac:true,_fmt:html')
  - simplified code (thanks to '_fmt:html' request)
  - issue 1359: fixed xpath of video length data

searx/engines/google_scholar.py
  - fetch_traits():  Fetch languages & regions from Google properties.
  - use *supported_domains* from traits
  - request(): include patents & citations
  - response(): fixed CAPTCHA detection (Scholar has its own CATCHA manager)
  - hardening XPath to iterate over results
  - fixed XPath of pub_type (has been change from gs_ct1 to gs_cgt2 class)
  - issue 1769 fixed: new request implementation is no longer incompatible

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

1 files changed, 63 insertions, 58 deletions

diff --git a/searx/engines/google_scholar.py b/searx/engines/google_scholar.py
index 38aaf904b..6f33d1e1a 100644
--- a/searx/engines/google_scholar.py
+++ b/searx/engines/google_scholar.py
@@ -1,19 +1,18 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 # lint: pylint
-"""Google (Scholar)
+"""This is the implementation of the Google Scholar engine.
 
-For detailed description of the *REST-full* API see: `Query Parameter
-Definitions`_.
-
-.. _Query Parameter Definitions:
-   https://developers.google.com/custom-search/docs/xml_results#WebSearch_Query_Parameter_Definitions
+Compared to other Google services the Scholar engine has a simple GET REST-API
+and there does not exists `async` API.  Even though the API slightly vintage we
+can make use of the :ref:`google API` to assemble the arguments of the GET
+request.
 """
 
-# pylint: disable=invalid-name
+from typing import TYPE_CHECKING
+from typing import Optional
 
 from urllib.parse import urlencode
 from datetime import datetime
-from typing import Optional
 from lxml import html
 
 from searx.utils import (
@@ -23,20 +22,21 @@ from searx.utils import (
     extract_text,
 )
 
+from searx.exceptions import SearxEngineCaptchaException
+
+from searx.engines.google import fetch_traits  # pylint: disable=unused-import
 from searx.engines.google import (
-    get_lang_info,
+    get_google_info,
     time_range_dict,
-    detect_google_sorry,
 )
+from searx.enginelib.traits import EngineTraits
 
-# pylint: disable=unused-import
-from searx.engines.google import (
-    fetch_traits,
-    supported_languages_url,
-    _fetch_supported_languages,
-)
+if TYPE_CHECKING:
+    import logging
 
-# pylint: enable=unused-import
+    logger: logging.Logger
+
+traits: EngineTraits
 
 # about
 about = {
@@ -52,53 +52,62 @@ about = {
 categories = ['science', 'scientific publications']
 paging = True
 language_support = True
-use_locale_domain = True
 time_range_support = True
 safesearch = False
 send_accept_language_header = True
 
 
-def time_range_url(params):
-    """Returns a URL query component for a google-Scholar time range based on
-    ``params['time_range']``.  Google-Scholar does only support ranges in years.
-    To have any effect, all the Searx ranges (*day*, *week*, *month*, *year*)
-    are mapped to *year*.  If no range is set, an empty string is returned.
-    Example::
+def time_range_args(params):
+    """Returns a dictionary with a time range arguments based on
+    ``params['time_range']``.
 
-        &as_ylo=2019
-    """
-    # as_ylo=2016&as_yhi=2019
-    ret_val = ''
-    if params['time_range'] in time_range_dict:
-        ret_val = urlencode({'as_ylo': datetime.now().year - 1})
-    return '&' + ret_val
+    Google Scholar supports a detailed search by year.  Searching by *last
+    month* or *last week* (as offered by SearXNG) is uncommon for scientific
+    publications and is not supported by Google Scholar.
 
+    To limit the result list when the users selects a range, all the SearXNG
+    ranges (*day*, *week*, *month*, *year*) are mapped to *year*.  If no range
+    is set an empty dictionary of arguments is returned.  Example;  when
+    user selects a time range (current year minus one in 2022):
 
-def request(query, params):
-    """Google-Scholar search request"""
+    .. code:: python
 
-    offset = (params['pageno'] - 1) * 10
-    lang_info = get_lang_info(params, supported_languages, language_aliases, False)
+        { 'as_ylo' : 2021 }
 
-    # subdomain is: scholar.google.xy
-    lang_info['subdomain'] = lang_info['subdomain'].replace("www.", "scholar.")
+    """
+    ret_val = {}
+    if params['time_range'] in time_range_dict:
+        ret_val['as_ylo'] = datetime.now().year - 1
+    return ret_val
 
-    query_url = (
-        'https://'
-        + lang_info['subdomain']
-        + '/scholar'
-        + "?"
-        + urlencode({'q': query, **lang_info['params'], 'ie': "utf8", 'oe': "utf8", 'start': offset})
-    )
 
-    query_url += time_range_url(params)
-    params['url'] = query_url
+def detect_google_captcha(dom):
+    """In case of CAPTCHA Google Scholar open its own *not a Robot* dialog and is
+    not redirected to ``sorry.google.com``.
+    """
+    if eval_xpath(dom, "//form[@id='gs_captcha_f']"):
+        raise SearxEngineCaptchaException()
+
 
-    params['cookies']['CONSENT'] = "YES+"
-    params['headers'].update(lang_info['headers'])
-    params['headers']['Accept'] = 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8'
+def request(query, params):
+    """Google-Scholar search request"""
 
-    # params['google_subdomain'] = subdomain
+    google_info = get_google_info(params, traits)
+    # subdomain is: scholar.google.xy
+    google_info['subdomain'] = google_info['subdomain'].replace("www.", "scholar.")
+
+    args = {
+        'q': query,
+        **google_info['params'],
+        'start': (params['pageno'] - 1) * 10,
+        'as_sdt': '2007',  # include patents / to disable set '0,5'
+        'as_vis': '0',  # include citations / to disable set '1'
+    }
+    args.update(time_range_args(params))
+
+    params['url'] = 'https://' + google_info['subdomain'] + '/scholar?' + urlencode(args)
+    params['cookies'] = google_info['cookies']
+    params['headers'].update(google_info['headers'])
     return params
 
 
@@ -139,19 +148,15 @@ def parse_gs_a(text: Optional[str]):
 
 
 def response(resp):  # pylint: disable=too-many-locals
-    """Get response from google's search request"""
+    """Parse response from Google Scholar"""
     results = []
 
-    detect_google_sorry(resp)
-
-    # which subdomain ?
-    # subdomain = resp.search_params.get('google_subdomain')
-
     # convert the text to dom
     dom = html.fromstring(resp.text)
+    detect_google_captcha(dom)
 
     # parse results
-    for result in eval_xpath_list(dom, '//div[@data-cid]'):
+    for result in eval_xpath_list(dom, '//div[@data-rp]'):
 
         title = extract_text(eval_xpath(result, './/h3[1]//a'))
 
@@ -159,7 +164,7 @@ def response(resp):  # pylint: disable=too-many-locals
             # this is a [ZITATION] block
             continue
 
-        pub_type = extract_text(eval_xpath(result, './/span[@class="gs_ct1"]'))
+        pub_type = extract_text(eval_xpath(result, './/span[@class="gs_ctg2"]'))
         if pub_type:
             pub_type = pub_type[1:-1].lower()