Revert "use xpyth-parser for parsing xpath (#91)"

This reverts commit e4531f4.

backend/requirements.in

@@ -11,5 +11,4 @@ alpino-query>=2.1.10
 celery[redis]>=5.2.0
 mwe-query>=0.0.4
 urllib3<=2.0.0
-psycopg2
-xpyth-parser
+psycopg2

backend/requirements.txt

@@ -101,9 +101,7 @@ idna==3.4
 iniconfig==2.0.0
     # via pytest
 isodate==0.6.1
-    # via
-    #   rdflib
-    #   xpyth-parser
+    # via rdflib
 jinja2==3.1.2
     # via spacy
 kombu==5.3.1
@@ -116,7 +114,6 @@ lxml==4.9.3
     #   folia
     #   sastadev
     #   tei-reader
-    #   xpyth-parser
 markupsafe==2.1.3
     # via jinja2
 murmurhash==1.0.9
@@ -158,9 +155,7 @@ pydantic==2.1.1
 pydantic-core==2.4.0
     # via pydantic
 pyparsing==3.1.1
-    # via
-    #   rdflib
-    #   xpyth-parser
+    # via rdflib
 pytest==7.4.0
     # via
     #   -r requirements.in
@@ -263,8 +258,6 @@ wcwidth==0.2.6
     # via prompt-toolkit
 xlsxwriter==3.1.2
     # via sastadev
-xpyth-parser==0.0.10
-    # via -r requirements.in
 
 # The following packages are considered to be unsafe in a requirements file:
 # setuptools

backend/search/basex_search.py

@@ -1,14 +1,12 @@
 """Auxiliary functions to facilitate searching in BaseX."""
 
 import lxml.etree
-import logging
 import string
 from io import StringIO
 from typing import List
-from xpyth_parser.parse import Parser
+
 from .types import BaseXMatch, Result
 
-log = logging.getLogger()
 
 ALLOWED_DBNAME_CHARS = string.ascii_letters + string.digits + \
     '!#$%&\'()+-=@[]^_`{}~.'
@@ -18,14 +16,11 @@
 def check_xpath(xpath: str) -> bool:
     """Return True if a string is (only) a valid XPath, otherwise False."""
     try:
-        # for some reason ".." isn't being properly parsed. since it's an abbreviation for
-        # parent::node(), we can replace it ahead of time
-        Parser(xpath.replace('..', 'parent::node()'), no_resolve=True)
+        lxml.etree.XPath(xpath)
+    except lxml.etree.XPathError:
+        return False
+    else:
         return True
-    except:
-        log.exception('XPath parse exception')
-
-    return False
 
 
 def check_db_name(db_name: str) -> bool: