use ruff rather than flake8 for python code linting (#37045)

The initially used config is compatible with flake8 rules, including all
pycodestyle (pep8) and pyflakes rules.

Testing: Broke some python files and used `mach test-tidy --all` to test
the linting.
Fixes: servo/servo#37041

Signed-off-by: zefr0x <zer0-x.7ty50@aleeas.com>

.flake8

@@ -1,18 +0,0 @@
-[flake8]
-ignore =
-    # trailing whitespace; the standard tidy process will enforce no trailing whitespace
-    W291,
-    # linebreak before binary operator; replaced by W504 - linebreak after binary operator
-    W503,
-    # 80 character line length; the standard tidy process will enforce line length
-    E501
-exclude =
-    # temporary local files
-    target
-    __pycache__
-    python/_venv*
-    # upstream
-    third_party
-    python/mach
-    components
-    tests

.vscode/extensions.json

@@ -16,6 +16,8 @@
         // IDL language support
         "mythmon.idl",
         // TOML files
-        "tamasfe.even-better-toml"
+        "tamasfe.even-better-toml",
+        // Python files
+        "charliermarsh.ruff"
     ]
 }

etc/profilicate.py

@@ -79,7 +79,7 @@ for (name, raw_samples) in sorted(iter(thread_data.items()), key=lambda x: threa
         for frame in sample[1]:
             if not frame['name']:
                 continue
-            if not frame['name'] in frameMap:
+            if frame['name'] not in frameMap:
                 frameMap[frame['name']] = len(frames)
                 frame_index = string_table.get(frame['name'])
                 frames.append([frame_index])

python/README.md

@@ -8,7 +8,7 @@ is the canonical repository for this code.
 
 # `tidy`
 
-servo-tidy is used to check licenses, line lengths, whitespace, flake8 on
+servo-tidy is used to check licenses, line lengths, whitespace, ruff on
 Python files, lock file versions, and more.
 
 # `wpt`

python/requirements.txt

@@ -8,10 +8,8 @@ mozlog == 8.0.0
 setuptools == 78.1.1
 toml == 0.9.2
 
-# For Python linting
+# For Python linting and formatting
-flake8 == 7.0.0
+ruff == 0.11.10
-pep8 == 1.5.7
-pyflakes == 3.2.0
 
 # For test-webidl
 ply == 3.8

python/tidy/tidy.py

@@ -356,19 +356,18 @@ def check_by_line(file_name: str, lines: list[bytes]):
             yield error
 
 
-def check_flake8(file_name, contents):
+def check_ruff_lints():
-    if not file_name.endswith(".py"):
-        return
-
-    output = ""
     try:
-        args = ["flake8", file_name]
+        args = ["ruff", "check", "--output-format", "json"]
         subprocess.check_output(args, universal_newlines=True)
     except subprocess.CalledProcessError as e:
-        output = e.output
+        for error in json.loads(e.output):
-    for error in output.splitlines():
+            yield (
-        _, line_num, _, message = error.split(":", 3)
+                os.path.join(".", os.path.relpath(error["filename"])),
-        yield line_num, message.strip()
+                error["location"]["row"],
+                f"[{error['code']}] {error['message']} ({error['url']})",
+            )
+
 
 
 def run_cargo_deny_lints():
@@ -976,17 +975,18 @@ def scan(only_changed_files=False, progress=False):
     directory_errors = check_directory_files(config['check_ext'])
     # standard checks
     files_to_check = filter_files('.', only_changed_files, progress)
-    checking_functions = (check_flake8, check_webidl_spec)
+    checking_functions = (check_webidl_spec,)
     line_checking_functions = (check_license, check_by_line, check_toml, check_shell,
                                check_rust, check_spec, check_modeline)
     file_errors = collect_errors_for_files(files_to_check, checking_functions, line_checking_functions)
 
+    python_errors = check_ruff_lints()
     cargo_lock_errors = run_cargo_deny_lints()
     wpt_errors = run_wpt_lints(only_changed_files)
 
     # chain all the iterators
     errors = itertools.chain(config_errors, directory_errors, file_errors,
-                             wpt_errors, cargo_lock_errors)
+                             python_errors, wpt_errors, cargo_lock_errors)
 
     colorama.init()
     error = None

python/tox.ini

@@ -1,3 +0,0 @@
-[flake8]
-filename = *.py
-max-line-length = 120

ruff.toml

@@ -0,0 +1,27 @@
+line-length = 120
+
+extend-exclude = [
+    # temporary local files
+    "target/**",
+    "__pycache__/**",
+    "python/_venv*/**",
+    # upstream
+    "third_party/**",
+    "python/mach/**",
+    "components/**",
+    "tests/**",
+]
+
+[lint]
+select = [
+    "E",
+    "W",
+    "F",
+]
+
+ignore = [
+    # Trailing whitespace; the standard tidy process will enforce no trailing whitespace
+    "W291",
+    # 80 character line length; the standard tidy process will enforce line length
+    "E501",
+]