fix: use locks to prevent concurrent parsing

The parser instances cannot be shared between threads as PyParsing is
not thread-safe, see pyparsing/pyparsing#89.

Fixes WEBLATE-1MFM

docs/changes.rst

@@ -11,6 +11,8 @@ Not yet released.
 
 **Bug fixes**
 
+* Avoid query parser crash in multi-threaded environments.
+
 **Compatibility**
 
 **Upgrading**

weblate/auth/models.py

@@ -8,7 +8,7 @@
 from collections import defaultdict
 from functools import cache as functools_cache
 from itertools import chain
-from typing import TYPE_CHECKING, TypedDict, cast
+from typing import TYPE_CHECKING, Literal, TypedDict, cast
 
 import sentry_sdk
 from appconf import AppConf
@@ -294,7 +294,12 @@ def all_admins(self, project):
     def order(self):
         return self.order_by("username")
 
-    def search(self, query: str, parser: str = "user", **context):
+    def search(
+        self,
+        query: str,
+        parser: Literal["plain", "user", "superuser"] = "user",
+        **context,
+    ):
         """High level wrapper for searching."""
         if parser == "plain":
             result = self.filter(

weblate/checks/flags.py

@@ -15,8 +15,9 @@
 
 from weblate.checks.models import CHECKS
 from weblate.checks.parser import (
+    FLAGS_PARSER,
+    FLAGS_PARSER_LOCK,
     SYNTAXCHARS,
-    FlagsParser,
     length_validation,
     multi_value_flag,
     single_value_flag,
@@ -91,7 +92,10 @@ def _parse_flags_text(flags: str) -> Iterator[str | tuple[Any, ...]]:
     state = 0
     name: str
     value: list[Any] = []
-    tokens = list(FlagsParser.parse_string(flags, parseAll=True))
+
+    with FLAGS_PARSER_LOCK:
+        tokens = list(FLAGS_PARSER.parse_string(flags, parse_all=True))
+
     for pos, token in enumerate(tokens):
         if state == 0 and token == ",":
             pass

weblate/checks/parser.py

@@ -2,9 +2,12 @@
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+from __future__ import annotations
+
 import re
+import threading
 
-from pyparsing import Optional, QuotedString, Regex, ZeroOrMore
+from pyparsing import Optional, ParserElement, QuotedString, Regex, ZeroOrMore
 
 
 def single_value_flag(func, validation=None):
@@ -32,7 +35,9 @@ def validate_length(val) -> None:
     return validate_length
 
 
-def multi_value_flag(func, minimum=1, maximum=None, modulo=None):
+def multi_value_flag(
+    func, minimum: int = 1, maximum: int | None = None, modulo: int | None = None
+):
     def parse_values(val):
         if modulo and len(val) % modulo != 0:
             msg = "Number of parameter is not even"
@@ -49,7 +54,7 @@ def parse_values(val):
 
 
 class RawQuotedString(QuotedString):
-    def __init__(self, quote_char, esc_char="\\") -> None:
+    def __init__(self, quote_char: str, esc_char: str = "\\") -> None:
         super().__init__(quote_char, esc_char=esc_char, convert_whitespace_escapes=True)
         # unlike the QuotedString this replaces only escaped quotes and not all chars
         self.unquote_scan_re = re.compile(
@@ -60,14 +65,20 @@ def __init__(self, quote_char, esc_char="\\") -> None:
 
 SYNTAXCHARS = {",", ":", '"', "'", "\\"}
 
-FlagName = Regex(r"""[^,:"' \r\n\t]([^,:"']*[^,:"' \r\n\t])?""")
 
-RegexString = "r" + RawQuotedString('"')
+def get_flags_parser() -> ParserElement:
+    flag_name = Regex(r"""[^,:"' \r\n\t]([^,:"']*[^,:"' \r\n\t])?""")
+
+    regex_string = "r" + RawQuotedString('"')
+
+    flag_param = Optional(
+        regex_string | flag_name | RawQuotedString("'") | RawQuotedString('"')
+    )
+
+    flag = flag_name + ZeroOrMore(":" + flag_param)
 
-FlagParam = Optional(
-    RegexString | FlagName | RawQuotedString("'") | RawQuotedString('"')
-)
+    return Optional(flag) + ZeroOrMore("," + Optional(flag))
 
-Flag = FlagName + ZeroOrMore(":" + FlagParam)
 
-FlagsParser = Optional(Flag) + ZeroOrMore("," + Optional(Flag))
+FLAGS_PARSER: ParserElement = get_flags_parser()
+FLAGS_PARSER_LOCK = threading.Lock()

weblate/utils/forms.py

@@ -3,6 +3,8 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 from __future__ import annotations
 
+from typing import Literal
+
 from crispy_forms.layout import Div, Field
 from crispy_forms.utils import TEMPLATE_PACK
 from django import forms
@@ -23,7 +25,9 @@
 
 
 class QueryField(forms.CharField):
-    def __init__(self, parser: str = "unit", **kwargs) -> None:
+    def __init__(
+        self, parser: Literal["unit", "user", "superuser"] = "unit", **kwargs
+    ) -> None:
         if "label" not in kwargs:
             kwargs["label"] = gettext_lazy("Query")
         if "required" not in kwargs:

weblate/utils/search.py

@@ -4,11 +4,12 @@
 
 from __future__ import annotations
 
+import threading
 from datetime import datetime, timedelta
 from functools import lru_cache, reduce
 from itertools import chain
 from operator import and_, or_
-from typing import TYPE_CHECKING, Any, cast, overload
+from typing import TYPE_CHECKING, Any, Literal, cast, overload
 
 from dateutil.parser import ParserError
 from dateutil.parser import parse as dateutil_parse
@@ -253,6 +254,8 @@ def human_date_parse(
     ) -> datetime | tuple[datetime, datetime]:
         tzinfo = timezone.get_current_timezone()
 
+        result: datetime | None
+
         try:
             # Here we inject 5:55:55 time and if that was not changed
             # during parsing, we assume it was not specified while
@@ -664,11 +667,12 @@ def is_field(self, text: str, context: dict) -> Q:
         return super().is_field(text, context)
 
 
-PARSERS = {
+PARSERS: dict[Literal["unit", "user", "superuser"], ParserElement] = {
     "unit": build_parser(UnitTermExpr),
     "user": build_parser(UserTermExpr),
     "superuser": build_parser(SuperuserUserTermExpr),
 }
+PARSER_LOCK = threading.Lock()
 
 
 def parser_to_query(obj, context: dict) -> Q:
@@ -696,13 +700,18 @@ def parser_to_query(obj, context: dict) -> Q:
 
 
 @lru_cache(maxsize=512)
-def parse_string(text: str, parser: str) -> ParseResults:
+def parse_string(
+    text: str, parser: Literal["unit", "user", "superuser"]
+) -> ParseResults:
     if "\x00" in text:
         msg = "Invalid query string."
         raise ValueError(msg)
-    return PARSERS[parser].parse_string(text, parse_all=True)
+    with PARSER_LOCK:
+        return PARSERS[parser].parse_string(text, parse_all=True)
 
 
-def parse_query(text: str, parser: str = "unit", **context) -> Q:
+def parse_query(
+    text: str, parser: Literal["unit", "user", "superuser"] = "unit", **context
+) -> Q:
     parsed = parse_string(text, parser)
     return parser_to_query(parsed, context)

weblate/utils/tests/test_search.py

@@ -1,8 +1,10 @@
 # Copyright © Michal Čihař <[email protected]>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
+from __future__ import annotations
 
 from datetime import UTC, datetime, timedelta
+from typing import Literal
 
 from django.db.models import F, Q
 from django.test import TestCase
@@ -24,7 +26,7 @@
 
 class SearchTestCase(TestCase):
     object_class = Unit
-    parser = "unit"
+    parser: Literal["unit", "user", "superuser"] = "unit"
 
     def assert_query(self, string, expected, exists=False, **context) -> None:
         result = parse_query(string, parser=self.parser, **context)