Python lint: Use ruff instead of flake8. NFC (#23085)

https://docs.astral.sh/ruff is an extremely fast Python linter and code
formatter, written in Rust. With over 800 linting rules, ruff can be
used to replace [Flake8](https://pypi.org/project/flake8/) (plus dozens
of plugins), [Black](https://github.com/psf/black),
[isort](https://pypi.org/project/isort/),
[pydocstyle](https://pypi.org/project/pydocstyle/),
[pyupgrade](https://pypi.org/project/pyupgrade/),
[autoflake](https://pypi.org/project/autoflake/), and more, all while
executing tens or hundreds of times faster than any individual tool.

Author: cclauss

.circleci/config.yml

@@ -419,12 +419,12 @@ jobs:
       - run: make -C site text
       - run: tools/maint/check_emcc_help_text.py
       - run: make -C site html
-  flake8:
+  ruff:
     executor: bionic
     steps:
       - checkout
       - pip-install
-      - run: python3 -m flake8 --show-source --statistics
+      - run: ruff check
   mypy:
     executor: bionic
     steps:
@@ -970,7 +970,7 @@ jobs:
 workflows:
   build-test:
     jobs:
-      - flake8
+      - ruff
       - mypy
       - eslint
       - build-docs

.flake8

@@ -55,8 +55,8 @@ pre-processor.  See [`.clang-format`][clang-format] for more details.
 ### Python Code
 
 We generally follow the pep8 standard with the major exception that we use 2
-spaces for indentation.  `flake8` is run on all PRs to ensure that python code
-conforms to this style.  See [`.flake8`][flake8] for more details.
+spaces for indentation.  `ruff` is run on all PRs to ensure that Python code
+conforms to this style.  See [`pyproject.toml`][pyproject.toml] for more details.
 
 #### Static Type Checking
 
@@ -304,7 +304,7 @@ To update our libraries to a newer musl release:
 [emsdk_tags]: https://github.com/emscripten-core/emsdk/tags
 [emscripten_tags]: https://github.com/emscripten-core/emscripten/tags
 [clang-format]: https://github.com/emscripten-core/emscripten/blob/main/.clang-format
-[flake8]: https://github.com/emscripten-core/emscripten/blob/main/.flake8
+[pyproject.toml]: https://github.com/emscripten-core/emscripten/blob/main/pyproject.toml
 [mypy]: https://github.com/emscripten-core/emscripten/blob/main/.mypy
 [update_docs]: https://github.com/emscripten-core/emscripten/blob/main/tools/maint/update_docs.py
 [llvm_repo]: https://github.com/llvm/llvm-project

docs/process.md

@@ -24,7 +24,7 @@ def main():
     not re.match(r"^[\w\W_][\w\W_\d]*$", sys.argv[1]) or \
     not hasattr(config, sys.argv[1]):
     print('Usage: em-config VAR_NAME', file=sys.stderr)
-    exit(1)
+    sys.exit(1)
 
   print(getattr(config, sys.argv[1]))
   return 0

em-config.py

@@ -1023,7 +1023,7 @@ def get_clang_command_asm():
   if state.mode == Mode.PCH:
     inputs = [i[1] for i in input_files]
     for header in inputs:
-      if not shared.suffix(header) in HEADER_ENDINGS:
+      if shared.suffix(header) not in HEADER_ENDINGS:
         exit_with_error(f'cannot mix precompiled headers with non-header inputs: {inputs} : {header}')
     cmd = get_clang_command() + inputs
     if options.output_file:
@@ -1127,7 +1127,15 @@ def version_string():
   return f'emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) {utils.EMSCRIPTEN_VERSION}{revision_suffix}'
 
 
-def parse_args(newargs):
+def parse_args(newargs):  # noqa: C901, PLR0912, PLR0915
+  """Future modifications should consider refactoring to reduce complexity.
+
+  * The McCabe cyclomatiic complexity is currently 117 vs 10 recommended.
+  * There are currently 115 branches vs 12 recommended.
+  * There are currently 302 statements vs 50 recommended.
+
+  To revalidate these numbers, run `ruff check --select=C901,PLR091`.
+  """
   options = EmccOptions()
   settings_changes = []
   user_js_defines = []

emcc.py

@@ -1583,7 +1583,15 @@ def parse_args(args):
   return parser.parse_args(args)
 
 
-def run(args):
+def run(args):  # noqa: C901, PLR0912, PLR0915
+  """Future modifications should consider refactoring to reduce complexity.
+
+  * The McCabe cyclomatiic complexity is currently 74 vs 10 recommended.
+  * There are currently 86 branches vs 12 recommended.
+  * There are currently 202 statements vs 50 recommended.
+
+  To revalidate these numbers, run `ruff check --select=C901,PLR091`.
+  """
   global browser_process, browser_exe, processname_killed_atexit, emrun_options, emrun_not_enabled_nag_printed
 
   options = emrun_options = parse_args(args)

emrun.py

@@ -121,10 +121,8 @@ def parse(self, filename):
     self.version = source_map_json['version']
     self.sources = source_map_json['sources']
 
-    vlq_map = {}
     chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
-    for i, c in enumerate(chars):
-      vlq_map[c] = i
+    vlq_map = {c: i for i, c in enumerate(chars)}
 
     def decodeVLQ(string):
       result = []

emsymbolizer.py

@@ -1,3 +1,70 @@
+[tool.ruff]
+exclude = [
+  "./cache/",
+  "./node_modules/",
+  "./site/source/_themes/",
+  "./site/source/conf.py",
+  "./system/lib/",
+  "./test/third_party/",
+  "./third_party/",
+  "./tools/filelock.py",
+  "./tools/scons/",
+  ".git",
+]
+
+lint.select = [
+  "ARG",
+  "ASYNC",
+  "B",
+  "C90",
+  "E",
+  "F",
+  "PERF",
+  "PL",
+  "W",
+  "YTT",
+]
+
+lint.ignore = [
+  "ARG001",
+  "ARG002",
+  "ARG005",
+  "B006",
+  "B011",
+  "B018",
+  "B023",
+  "B026",
+  "B904",
+  "E402",
+  "E501",
+  "E721",
+  "E741",
+  "PERF203",
+  "PERF401",
+  "PLR1704",
+  "PLR1714",
+  "PLR5501",
+  "PLW0602",
+  "PLW0603",
+  "PLW1510",
+  "PLW2901",
+]
+
+lint.per-file-ignores."emrun.py" = [ "PLE0704" ]
+
+lint.mccabe.max-complexity = 48 # Recommended: 10
+
+lint.pylint.allow-magic-value-types = [
+  "bytes",
+  "float",
+  "int",
+  "str",
+]
+lint.pylint.max-args = 15 # Recommended: 5
+lint.pylint.max-branches = 49 # Recommended: 12
+lint.pylint.max-returns = 16 # Recommended: 6
+lint.pylint.max-statements = 142 # Recommended: 50
+
 [tool.coverage.run]
 source = [ "." ]
 omit = [

pyproject.toml

@@ -1,14 +1,12 @@
 # TODO(sbc): switch to using Pipenv since it seems like that way to go
 # these day managing python deps.
-# These requirements are only needed for developers who want to run flake8 on
+# These requirements are only needed for developers who want to run ruff on
 # the codebase and generate docs using Sphinx, not for users of emscripten.
 # Install with `pip3 install -r requirements-dev.txt`
 
-flake8==5.0.4
-flake8-bugbear==22.9.23
-flake8-unused-arguments==0.0.11
 coverage[toml]==5.5
 mypy==0.971
+ruff==0.8.2
 types-requests==2.27.14
 unittest-xml-reporting==3.1.0
 

requirements-dev.txt

@@ -134,14 +134,14 @@ def format_comparison(a, b):
     total_time_html_scalar = 0
     total_time_html_simd = 0
 
-    for chart_name in charts_native.keys():
+    for chart_name, chart_native_results in charts_native.items():
         # Extract data for each chart.
         categories = []
         nativeScalarResults = []
         nativeSimdResults = []
         htmlScalarResults = []
         htmlSimdResults = []
-        native_results = charts_native[chart_name]
+        native_results = chart_native_results
         wasm_results = charts_html[chart_name]
         textual_results_native = '<p>'
         textual_results_html = '<p>'

test/benchmark/benchmark_sse.py

@@ -106,7 +106,7 @@ def check_js_engines():
   working_engines = [e for e in config.JS_ENGINES if jsrun.check_engine(e)]
   if len(working_engines) < len(config.JS_ENGINES):
     print('Not all the JS engines in JS_ENGINES appears to work.')
-    exit(1)
+    sys.exit(1)
 
   if common.EMTEST_ALL_ENGINES:
     print('(using ALL js engines)')
@@ -311,11 +311,9 @@ def load_test_suites(args, modules, start_at, repeat):
 def flattened_tests(loaded_tests):
   tests = []
   for subsuite in loaded_tests:
-    for test in subsuite:
-      tests.append(test)
+    tests.extend(subsuite)
   return tests
 
-
 def suite_for_module(module, tests):
   suite_supported = module.__name__ in ('test_core', 'test_other', 'test_posixtest')
   if not common.EMTEST_SAVE_DIR and not shared.DEBUG:

test/runner.py

@@ -354,7 +354,15 @@ def generate_object_file(data_files):
   shared.check_call(cmd)
 
 
-def main():
+def main():  # noqa: C901, PLR0912, PLR0915
+  """Future modifications should consider refactoring to reduce complexity.
+
+  * The McCabe cyclomatiic complexity is currently 60 vs 10 recommended.
+  * There are currently 63 branches vs 12 recommended.
+  * There are currently 151 statements vs 50 recommended.
+
+  To revalidate these numbers, run `ruff check --select=C901,PLR091`.
+  """
   if len(sys.argv) == 1:
     err('''Usage: file_packager TARGET [--preload A [B..]] [--embed C [D..]] [--exclude E [F..]]] [--js-output=OUTPUT.js] [--no-force] [--use-preload-cache] [--indexedDB-name=EM_PRELOAD_CACHE] [--separate-metadata] [--lz4] [--use-preload-plugins] [--no-node]
   See the source for more details.''')

tools/file_packager.py

@@ -631,7 +631,15 @@ def check_browser_versions():
 
 
 @ToolchainProfiler.profile_block('linker_setup')
-def phase_linker_setup(options, state, newargs):
+def phase_linker_setup(options, state, newargs):  # noqa: C901, PLR0912, PLR0915
+  """Future modifications should consider refactoring to reduce complexity.
+
+  * The McCabe cyclomatiic complexity is currently 251 vs 10 recommended.
+  * There are currently 262 branches vs 12 recommended.
+  * There are currently 578 statements vs 50 recommended.
+
+  To revalidate these numbers, run `ruff check --select=C901,PLR091`.
+  """
   system_libpath = '-L' + str(cache.get_lib_dir(absolute=True))
   state.append_link_flag(system_libpath)
 

tools/link.py

@@ -386,10 +386,18 @@ def type_to_cdec(raw):
   return ret + '*'
 
 
-def render_function(class_name, func_name, sigs, return_type, non_pointer,
+def render_function(class_name, func_name, sigs, return_type, non_pointer,  # noqa: C901, PLR0912, PLR0915
                     copy, operator, constructor, is_static, func_scope,
                     call_content=None, const=False, array_attribute=False,
                     bind_to=None):
+  """Future modifications should consider refactoring to reduce complexity.
+
+  * The McCabe cyclomatiic complexity is currently 67 vs 10 recommended.
+  * There are currently 79 branches vs 12 recommended.
+  * There are currently 195 statements vs 50 recommended.
+
+  To revalidate these numbers, run `ruff check --select=C901,PLR091`.
+  """
   legacy_mode = CHECKS not in ['ALL', 'FAST']
   all_checks = CHECKS == 'ALL'