Switch to ruff instead of flake8. (#14633)

ruff is a flake8-compatible Python linter written in Rust.
It supports the flake8 plugins that we use and is significantly
faster in testing.

Author: clokep

.flake8

@@ -53,7 +53,7 @@ jobs:
       - run: scripts-dev/check_schema_delta.py --force-colors
 
   lint:
-    uses: "matrix-org/backend-meta/.github/workflows/python-poetry-ci.yml@v1"
+    uses: "matrix-org/backend-meta/.github/workflows/python-poetry-ci.yml@v2"
     with:
       typechecking-extras: "all"
 

.github/workflows/tests.yml

@@ -0,0 +1 @@
+Use [ruff](https://github.com/charliermarsh/ruff/) instead of flake8.

changelog.d/14633.misc

@@ -40,6 +40,46 @@ target-version = ['py37', 'py38', 'py39', 'py310']
 # https://black.readthedocs.io/en/stable/usage_and_configuration/file_collection_and_discovery.html#gitignore
 # Use `extend-exclude` if you want to exclude something in addition to this.
 
+[tool.ruff]
+line-length = 88
+
+# See https://github.com/charliermarsh/ruff/#pycodestyle
+# for error codes. The ones we ignore are:
+#  E731: do not assign a lambda expression, use a def
+#  E501: Line too long (black enforces this for us)
+#
+# See https://github.com/charliermarsh/ruff/#pyflakes
+#  F401: unused import
+#  F811: Redefinition of unused
+#  F821: Undefined name
+#
+# flake8-bugbear compatible checks. Its error codes are described at
+# https://github.com/charliermarsh/ruff/#flake8-bugbear
+#  B019: Use of functools.lru_cache or functools.cache on methods can lead to memory leaks
+#  B023: Functions defined inside a loop must not use variables redefined in the loop
+#  B024: Abstract base class with no abstract method.
+ignore = [
+    "B019",
+    "B023",
+    "B024",
+    "E501",
+    "E731",
+    "F401",
+    "F811",
+    "F821",
+]
+select = [
+    # pycodestyle checks.
+    "E",
+    "W",
+    # pyflakes checks.
+    "F",
+    # flake8-bugbear checks.
+    "B0",
+    # flake8-comprehensions checks.
+    "C4",
+]
+
 [tool.isort]
 line_length = 88
 sections = ["FUTURE", "STDLIB", "THIRDPARTY", "TWISTED", "FIRSTPARTY", "TESTS", "LOCALFOLDER"]
@@ -274,12 +314,10 @@ all = [
 ]
 
 [tool.poetry.dev-dependencies]
-## We pin black so that our tests don't start failing on new releases.
+# We pin black so that our tests don't start failing on new releases.
 isort = ">=5.10.1"
 black = ">=22.3.0"
-flake8-comprehensions = "*"
-flake8-bugbear = ">=21.3.2"
-flake8 = "*"
+ruff = "0.0.189"
 
 # Typechecking
 mypy = "*"

poetry.lock

@@ -1,9 +1,8 @@
 #!/usr/bin/env bash
 #
 # Runs linting scripts over the local Synapse checkout
-# isort - sorts import statements
 # black - opinionated code formatter
-# flake8 - lints and finds mistakes
+# ruff - lints and finds mistakes
 
 set -e
 
@@ -105,6 +104,6 @@ set -x
 isort "${files[@]}"
 python3 -m black "${files[@]}"
 ./scripts-dev/config-lint.sh
-flake8 "${files[@]}"
+ruff "${files[@]}"
 ./scripts-dev/check_pydantic_models.py lint
 mypy

pyproject.toml

@@ -14,6 +14,8 @@
 
 # Stub for frozendict.
 
+from __future__ import annotations
+
 from typing import Any, Hashable, Iterable, Iterator, Mapping, Tuple, TypeVar, overload
 
 _KT = TypeVar("_KT", bound=Hashable)  # Key type.

scripts-dev/lint.sh

@@ -14,6 +14,8 @@
 
 # Stub for PyICU.
 
+from __future__ import annotations
+
 class Locale:
     @staticmethod
     def getDefault() -> Locale: ...

stubs/frozendict.pyi

@@ -2,6 +2,8 @@
 # https://github.com/grantjenks/python-sortedcontainers/blob/eea42df1f7bad2792e8da77335ff888f04b9e5ae/sortedcontainers/sorteddict.pyi
 # (from https://github.com/grantjenks/python-sortedcontainers/pull/107)
 
+from __future__ import annotations
+
 from typing import (
     Any,
     Callable,

stubs/icu.pyi

@@ -2,6 +2,8 @@
 # https://github.com/grantjenks/python-sortedcontainers/blob/a419ffbd2b1c935b09f11f0971696e537fd0c510/sortedcontainers/sortedlist.pyi
 # (from https://github.com/grantjenks/python-sortedcontainers/pull/107)
 
+from __future__ import annotations
+
 from typing import (
     Any,
     Callable,