fix: remove unreachable backports.functools_lru_cache fallback

`functools.lru_cache` has been in the standard library since Python 3.2.
The project requires Python >=3.10, so the `except ImportError` branch
importing `backports.functools_lru_cache` can never execute.

Remove the try/except block and keep only the direct stdlib import.
Also remove `types-backports` from dev dependencies, `backports` from
`[tool.deptry.known_first_party]`, and `types-backports` from the
DEP002 ignore list in `pyproject.toml`.

CHANGELOG.md

@@ -32,6 +32,7 @@
 - fix: loader.py reads entire file for magic byte check @williballenthin #3029
 - fix: freeze/__init__.py: logically impossible condition @williballenthin #3030
 - fix: EXTENSIONS_ELF never referenced @williballenthin #3031
+- fix: remove unreachable backports.functools_lru_cache fallback and dead dependency @williballenthin
 
 ### capa Explorer Web
 

capa/rules/__init__.py

@@ -23,18 +23,9 @@ import logging
 import binascii
 import collections
 from enum import Enum
-from pathlib import Path
-
-from capa.helpers import assert_never
-
-try:
-    from functools import lru_cache
-except ImportError:
-    # need to type ignore this due to mypy bug here (duplicate name):
-    # https://github.com/python/mypy/issues/1153
-    from backports.functools_lru_cache import lru_cache  # type: ignore
-
 from typing import Any, Union, Callable, Iterator, Optional, cast
+from pathlib import Path
+from functools import lru_cache
 from dataclasses import asdict, dataclass
 
 import yaml
@@ -51,6 +42,7 @@ import capa.features.insn
 import capa.features.common
 import capa.features.basicblock
 from capa.engine import Statement, FeatureSet
+from capa.helpers import assert_never
 from capa.features.com import ComType
 from capa.features.common import MAX_BYTES_FEATURE_SIZE, Feature
 from capa.features.address import Address
@@ -1129,7 +1121,7 @@ class Rule:
         return cls(name, scopes, build_statements(statements[0], scopes), meta, definition)  # type: ignore[arg-type]  # build_statements infers wide union but top-level always returns Statement
 
     @staticmethod
-    @lru_cache()
+    @lru_cache
     def _get_yaml_loader():
         try:
             # prefer to use CLoader to be fast, see #306 / CSafeLoader is the same as CLoader but with safe loading

pyproject.toml

@@ -139,7 +139,6 @@ dev = [
     "PyGithub==2.9.0",
     "bump-my-version==1.3.0",
     # type stubs for mypy
-    "types-backports==0.1.3",
     "types-colorama==0.4.15.11",
     "types-PyYAML==6.0.8",
     "types-psutil==7.2.0.20251228",
@@ -178,7 +177,6 @@ extend_exclude = [
 
 # dependencies marked as first party, to inform deptry that they are local
 known_first_party = [
-    "backports",
     "binaryninja",
     "flirt",
     "ghidra",
@@ -219,7 +217,6 @@ DEP002 = [
     "pytest-sugar",
     "ruff",
     "setuptools",
-    "types-backports",
     "types-colorama",
     "types-protobuf",
     "types-psutil",

tests/test_helpers.py

@@ -106,7 +106,6 @@ def test_is_dev_environment():
     assert capa.helpers.is_dev_environment() is True
 
 
-<<<<<<< HEAD
 def test_load_one_jsonl_from_path_gz():
     result = capa.helpers.load_one_jsonl_from_path(DRAKVUF_LOG_GZ)
     assert isinstance(result, dict)