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Fix memoisation of lazy parser & bump version #255

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Merged
merged 1 commit into from
Feb 1, 2025
Merged

Fix memoisation of lazy parser & bump version #255

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2 changes: 1 addition & 1 deletion pyproject.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ build-backend = "setuptools.build_meta"
[project]
name = "ua-parser"
description = "Python port of Browserscope's user agent parser"
version = "1.0.0"
version = "1.0.1"
readme = "README.rst"
requires-python = ">=3.9"
dependencies = ["ua-parser-builtins"]
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29 changes: 21 additions & 8 deletions src/ua_parser/__init__.py
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Expand Up @@ -41,7 +41,8 @@
]

import importlib.util
from typing import Callable, Optional
import threading
from typing import Callable, Optional, cast

from .basic import Resolver as BasicResolver
from .caching import CachingResolver, S3Fifo as Cache
Expand Down Expand Up @@ -78,7 +79,7 @@
)


VERSION = (1, 0, 0)
VERSION = (1, 0, 1)


class Parser:
Expand Down Expand Up @@ -135,15 +136,27 @@ def parse_device(self: Resolver, ua: str) -> Optional[Device]:
initialisation, rather than pay for it at first call.
"""

_lazy_globals_lock = threading.Lock()


def __getattr__(name: str) -> Parser:
global parser
if name == "parser":
if RegexResolver or Re2Resolver or IS_GRAAL:
matchers = load_lazy_builtins()
else:
matchers = load_builtins()
return Parser.from_matchers(matchers)
with _lazy_globals_lock:
if name == "parser":
# if two threads access `ua_parser.parser` before it's
# initialised, the second one will wait until the first
# one's finished by which time the parser global should be
# set and can be returned with no extra work
if p := globals().get("parser"):
return cast(Parser, p)

if RegexResolver or Re2Resolver or IS_GRAAL:
matchers = load_lazy_builtins()
else:
matchers = load_builtins()
parser = Parser.from_matchers(matchers)
return parser

raise AttributeError(f"module {__name__!r} has no attribute {name!r}")


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17 changes: 17 additions & 0 deletions tests/test_convenience_parser.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,23 @@
import ua_parser
from ua_parser import Domain, Parser, PartialResult, Result


def test_parser_memoized() -> None:
"""The global parser should be lazily instantiated but memoized"""
# ensure there is no global parser
vars(ua_parser).pop("parser", None)

p1 = ua_parser.parser
p2 = ua_parser.parser

assert p1 is p2

# force the creation of a clean parser
del ua_parser.parser
p3 = ua_parser.parser
assert p3 is not p1


def resolver(s: str, d: Domain) -> PartialResult:
return PartialResult(d, None, None, None, s)

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