Install flake8-bugbear plugin and fix resulting warnings. NFC (#17173)

.flake8

@@ -1,5 +1,5 @@
 [flake8]
-ignore = E111,E114,E501,E261,E266,E121,E402,E241,W504,E741
+ignore = E111,E114,E501,E261,E266,E121,E402,E241,W504,E741,B011
 exclude =
  ./third_party/, # third-party code
  ./tools/filelock.py, # third-party code

emsymbolizer.py

@@ -87,7 +87,7 @@ def decodeVLQ(string):
       result = []
       shift = 0
       value = 0
-      for i, c in enumerate(string):
+      for c in string:
         try:
           integer = vlq_map[c]
         except ValueError:
@@ -107,7 +107,7 @@ def decodeVLQ(string):
     line = 1
     col = 1
     name = 0
-    for i, segment in enumerate(source_map_json['mappings'].split(',')):
+    for segment in source_map_json['mappings'].split(','):
       data = decodeVLQ(segment)
       info = []
 

requirements-dev.txt

@@ -5,6 +5,7 @@
 # Install with `pip3 install -r requirements-dev.txt`
 
 flake8==3.9.0
+flake8-bugbear==22.4.25
 flake8-unused-arguments==0.0.6
 coverage==5.5
 

site/source/get_wiki.py

@@ -115,7 +115,7 @@ def ConvertFilesToRst():
         length = len(title)
         # print length
         headerbar = ''
-        for number in range(length):
+        for _ in range(length):
             headerbar += '='
         page_reference = filenamestripped
         page_reference_link_text = '.. _%s:\n\n' % page_reference

tests/common.py

@@ -643,7 +643,7 @@ def verify_es5(self, filename):
       self.fail('es-check failed to verify ES5 output compliance')
 
   # Build JavaScript code from source code
-  def build(self, filename, libraries=[], includes=[], force_c=False, js_outfile=True, emcc_args=[], output_basename=None):
+  def build(self, filename, libraries=None, includes=None, force_c=False, js_outfile=True, emcc_args=None, output_basename=None):
     suffix = '.js' if js_outfile else '.wasm'
     compiler = [compiler_for(filename, force_c)]
     if compiler[0] == EMCC:
@@ -661,11 +661,16 @@ def build(self, filename, libraries=[], includes=[], force_c=False, js_outfile=T
     else:
       basename = os.path.basename(filename)
       output = shared.unsuffixed(basename) + suffix
-    cmd = compiler + [filename, '-o', output] + self.get_emcc_args(main_file=True) + emcc_args + libraries
+    cmd = compiler + [filename, '-o', output] + self.get_emcc_args(main_file=True)
+    if emcc_args:
+      cmd += emcc_args
+    if libraries:
+      cmd += libraries
     if shared.suffix(filename) not in ('.i', '.ii'):
       # Add the location of the test file to include path.
       cmd += ['-I.']
-      cmd += ['-I' + str(include) for include in includes]
+      if includes:
+        cmd += ['-I' + str(include) for include in includes]
 
     self.run_process(cmd, stderr=self.stderr_redirect if not DEBUG else None)
     self.assertExists(output)
@@ -729,7 +734,7 @@ def measure_wasm_code_lines(self, wasm):
     non_data_lines = [line for line in wat_lines if '(data ' not in line]
     return len(non_data_lines)
 
-  def run_js(self, filename, engine=None, args=[],
+  def run_js(self, filename, engine=None, args=None,
              output_nicerizer=None,
              assert_returncode=0,
              interleaved_output=True):
@@ -897,9 +902,11 @@ def get_build_dir(self):
     ensure_dir(ret)
     return ret
 
-  def get_library(self, name, generated_libs, configure=['sh', './configure'],
-                  configure_args=[], make=['make'], make_args=None,
+  def get_library(self, name, generated_libs, configure=['sh', './configure'],  # noqa
+                  configure_args=None, make=None, make_args=None,
                   env_init=None, cache_name_extra='', native=False):
+    if make is None:
+      make = ['make']
     if env_init is None:
       env_init = {}
     if make_args is None:
@@ -929,9 +936,10 @@ def get_library(self, name, generated_libs, configure=['sh', './configure'],
       return generated_libs
 
     print(f'<building and saving {cache_name} into cache>', file=sys.stderr)
-    if configure is not None:
-      # Avoid += so we don't mutate the default arg
-      configure = configure + configure_args
+    if configure and configure_args:
+      # Make to copy to avoid mutating default param
+      configure = list(configure)
+      configure += configure_args
 
     cflags = ' '.join(emcc_args)
     env_init.setdefault('CFLAGS', cflags)
@@ -958,7 +966,7 @@ def run_process(self, cmd, check=True, **args):
         print(e.stderr)
         self.fail(f'subprocess exited with non-zero return code({e.returncode}): `{shared.shlex_join(cmd)}`')
 
-  def emcc(self, filename, args=[], output_filename=None, **kwargs):
+  def emcc(self, filename, args=[], output_filename=None, **kwargs):  # noqa
     cmd = [compiler_for(filename), filename] + self.get_emcc_args(ldflags='-c' not in args) + args
     if output_filename:
       cmd += ['-o', output_filename]
@@ -1047,9 +1055,10 @@ def _test_dylink_dso_needed(self, do_run):
 
     so = '.wasm' if self.is_wasm() else '.js'
 
-    def ccshared(src, linkto=[]):
+    def ccshared(src, linkto=None):
       cmdv = [EMCC, src, '-o', shared.unsuffixed(src) + so, '-sSIDE_MODULE'] + self.get_emcc_args()
-      cmdv += linkto
+      if linkto:
+        cmdv += linkto
       self.run_process(cmdv)
 
     ccshared('liba.cpp')
@@ -1076,8 +1085,9 @@ def ccshared(src, linkto=[]):
       ''',
            'a: loaded\na: b (prev: (null))\na: c (prev: b)\n', emcc_args=extra_args)
 
+    extra_args = []
     for libname in ['liba', 'libb', 'libc']:
-      self.emcc_args += ['--embed-file', libname + so]
+      extra_args += ['--embed-file', libname + so]
     do_run(r'''
       #include <assert.h>
       #include <dlfcn.h>
@@ -1103,7 +1113,7 @@ def ccshared(src, linkto=[]):
         return 0;
       }
     ''' % locals(),
-           'a: loaded\na: b (prev: (null))\na: c (prev: b)\n')
+           'a: loaded\na: b (prev: (null))\na: c (prev: b)\n', emcc_args=extra_args)
 
   def filtered_js_engines(self):
     for engine in self.js_engines:
@@ -1140,12 +1150,12 @@ def do_run_in_out_file_test(self, *path, **kwargs):
     return self._build_and_run(srcfile, expected, **kwargs)
 
   ## Does a complete test - builds, runs, checks output, etc.
-  def _build_and_run(self, filename, expected_output, args=[], output_nicerizer=None,
+  def _build_and_run(self, filename, expected_output, args=None, output_nicerizer=None,
                      no_build=False,
-                     libraries=[],
-                     includes=[],
+                     libraries=None,
+                     includes=None,
                      assert_returncode=0, assert_identical=False, assert_all=False,
-                     check_for_error=True, force_c=False, emcc_args=[],
+                     check_for_error=True, force_c=False, emcc_args=None,
                      interleaved_output=True,
                      regex=False,
                      output_basename=None):
@@ -1745,11 +1755,11 @@ def build_library(name,
                   generated_libs,
                   configure,
                   make,
-                  make_args=[],
-                  cache=None,
-                  cache_name=None,
-                  env_init={},
-                  native=False):
+                  make_args,
+                  cache,
+                  cache_name,
+                  env_init,
+                  native):
   """Build a library and cache the result.  We build the library file
   once and cache it for all our tests. (We cache in memory since the test
   directory is destroyed and recreated for each test. Note that we cache

tests/gen_large_switchcase.py

@@ -10,7 +10,7 @@
 cases = ''
 i = 1
 incr = 1
-for x in range(0, num_cases):
+for _ in range(0, num_cases):
   cases += '  case ' + str(i) + ': return "' + str(i) + str(i) + str(i) + '";\n'
   i += incr
   incr = (incr % 5) + 1

tests/jsrun.py

@@ -16,7 +16,8 @@
 DEFAULT_TIMEOUT = 5 * 60
 
 
-def make_command(filename, engine, args=[]):
+def make_command(filename, engine, args=None):
+  args = args or []
   # if no engine is needed, indicated by None, then there is a native executable
   # provided which we can just run
   if engine[0] is None:
@@ -85,7 +86,7 @@ def require_engine(engine):
     sys.exit(1)
 
 
-def run_js(filename, engine, args=[],
+def run_js(filename, engine, args=None,
            stdin=None, stdout=PIPE, stderr=None, cwd=None,
            full_output=False, assert_returncode=0, skip_check=False,
            timeout=DEFAULT_TIMEOUT):

tests/runner.py

@@ -128,7 +128,7 @@ def get_all_tests(modules):
 def tests_with_expanded_wildcards(args, all_tests):
   # Process wildcards, e.g. "browser.test_pthread_*" should expand to list all pthread tests
   new_args = []
-  for i, arg in enumerate(args):
+  for arg in args:
     if '*' in arg:
       if arg.startswith('skip:'):
         arg = arg[5:]

tests/test_benchmark.py

@@ -65,7 +65,7 @@ def prepare(self):
   def bench(self, args, output_parser=None, reps=TEST_REPS, expected_output=None):
     self.times = []
     self.reps = reps
-    for i in range(reps):
+    for _ in range(reps):
       start = time.time()
       output = self.run(args)
       if expected_output is not None and expected_output not in output:
@@ -125,13 +125,15 @@ def get_size_text(self):
 
 
 class NativeBenchmarker(Benchmarker):
-  def __init__(self, name, cc, cxx, args=[OPTIMIZATIONS]):
+  def __init__(self, name, cc, cxx, args=None):
     self.name = name
     self.cc = cc
     self.cxx = cxx
-    self.args = args.copy()
+    self.args = args or [OPTIMIZATIONS]
 
   def build(self, parent, filename, args, shared_args, emcc_args, native_args, native_exec, lib_builder, has_output_parser):
+    native_args = native_args or []
+    shared_args = shared_args or []
     self.parent = parent
     if lib_builder:
       env = {'CC': self.cc, 'CXX': self.cxx, 'CXXFLAGS': "-Wno-c++11-narrowing"}
@@ -173,15 +175,17 @@ def run_binaryen_opts(filename, opts):
 
 
 class EmscriptenBenchmarker(Benchmarker):
-  def __init__(self, name, engine, extra_args=[], env={}, binaryen_opts=[]):
+  def __init__(self, name, engine, extra_args=None, env=None, binaryen_opts=None):
     self.name = name
     self.engine = engine
-    self.extra_args = extra_args.copy()
+    self.extra_args = extra_args or []
     self.env = os.environ.copy()
-    self.env.update(env)
-    self.binaryen_opts = binaryen_opts.copy()
+    if env:
+      self.env.update(env)
+    self.binaryen_opts = binaryen_opts or []
 
   def build(self, parent, filename, args, shared_args, emcc_args, native_args, native_exec, lib_builder, has_output_parser):
+    emcc_args = emcc_args or []
     self.filename = filename
     llvm_root = self.env.get('LLVM') or config.LLVM_ROOT
     if lib_builder:
@@ -190,7 +194,7 @@ def build(self, parent, filename, args, shared_args, emcc_args, native_args, nat
       # systems (like zlib) if they see a CFLAGS it will override all their
       # default flags, including optimizations.
       env_init['CFLAGS'] = ' '.join(LLVM_FEATURE_FLAGS + [OPTIMIZATIONS] + self.extra_args)
-      emcc_args = emcc_args + lib_builder('js_' + llvm_root, native=False, env_init=env_init)
+      emcc_args += lib_builder('js_' + llvm_root, native=False, env_init=env_init)
     final = os.path.dirname(filename) + os.path.sep + self.name + ('_' if self.name else '') + os.path.basename(filename) + '.js'
     final = final.replace('.cpp', '')
     try_delete(final)
@@ -201,7 +205,9 @@ def build(self, parent, filename, args, shared_args, emcc_args, native_args, nat
       '-sENVIRONMENT=node,shell',
       '-sBENCHMARK=%d' % (1 if IGNORE_COMPILATION and not has_output_parser else 0),
       '-o', final
-    ] + shared_args + LLVM_FEATURE_FLAGS
+    ] + LLVM_FEATURE_FLAGS
+    if shared_args:
+      cmd += shared_args
     if common.EMTEST_FORCE64:
       cmd += ['--profiling']
     else:
@@ -281,11 +287,11 @@ def get_output_files(self):
 
 
 class CheerpBenchmarker(Benchmarker):
-  def __init__(self, name, engine, args=[OPTIMIZATIONS], binaryen_opts=[]):
+  def __init__(self, name, engine, args=None, binaryen_opts=None):
     self.name = name
     self.engine = engine
-    self.args = args.copy()
-    self.binaryen_opts = binaryen_opts.copy()
+    self.args = args or [OPTIMIZATIONS]
+    self.binaryen_opts = binaryen_opts or []
 
   def build(self, parent, filename, args, shared_args, emcc_args, native_args, native_exec, lib_builder, has_output_parser):
     cheerp_args = [
@@ -435,8 +441,8 @@ def hardcode_arguments(self, code):
     ''' % DEFAULT_ARG
     return code
 
-  def do_benchmark(self, name, src, expected_output='FAIL', args=[],
-                   emcc_args=[], native_args=[], shared_args=[],
+  def do_benchmark(self, name, src, expected_output='FAIL', args=None,
+                   emcc_args=None, native_args=None, shared_args=None,
                    force_c=False, reps=TEST_REPS, native_exec=None,
                    output_parser=None, args_processor=None, lib_builder=None,
                    skip_native=False):
@@ -809,7 +815,7 @@ def zzz_test_corrections64(self):
     '''
     self.do_benchmark('corrections64', src, 'final:')
 
-  def fasta(self, name, double_rep, emcc_args=[]):
+  def fasta(self, name, double_rep):
     src = read_file(test_file('fasta.cpp')).replace('double', double_rep)
     src = src.replace('   const size_t n = ( argc > 1 ) ? atoi( argv[1] ) : 512;', '''
       int n;