Don't use len() to test for container emptiness

I ran the numbers once before (it's in the meson history) but it's
*much* faster to *not* use len for testing if a container is empty or
not.

mesonbuild/backend/xcodebackend.py

@@ -748,7 +748,7 @@ class XCodeBackend(backends.Backend):
                     gargs = self.build.global_args.get(lang, [])
                     targs = target.get_extra_args(lang)
                     args = pargs + gargs + targs
-                    if len(args) > 0:
+                    if args:
                         langargs[langnamemap[lang]] = args
                 symroot = os.path.join(self.environment.get_build_dir(), target.subdir)
                 self.write_line('%s /* %s */ = {' % (valid, buildtype))
@@ -783,7 +783,7 @@ class XCodeBackend(backends.Backend):
                         self.write_line('GCC_PREFIX_HEADER = "$(PROJECT_DIR)/%s";' % relative_pch_path)
                 self.write_line('GCC_PREPROCESSOR_DEFINITIONS = "";')
                 self.write_line('GCC_SYMBOLS_PRIVATE_EXTERN = NO;')
-                if len(headerdirs) > 0:
+                if headerdirs:
                     quotedh = ','.join(['"\\"%s\\""' % i for i in headerdirs])
                     self.write_line('HEADER_SEARCH_PATHS=(%s);' % quotedh)
                 self.write_line('INSTALL_PATH = "%s";' % install_path)

mesonbuild/compilers/c.py

@@ -248,7 +248,7 @@ class CCompiler(Compiler):
         for d in dirs:
             files = [f for f in os.listdir(d) if f.endswith('.so') and os.path.isfile(os.path.join(d, f))]
             # if no files, accept directory and move on
-            if len(files) == 0:
+            if not files:
                 retval.append(d)
                 continue
             file_to_check = os.path.join(d, files[0])

mesonbuild/compilers/compilers.py

@@ -1506,7 +1506,7 @@ def gnulike_default_include_dirs(compiler, lang):
                 break
             else:
                 paths.append(line[1:])
-    if len(paths) == 0:
+    if not paths:
         mlog.warning('No include directory found parsing "{cmd}" output'.format(cmd=" ".join(cmd)))
     return paths
 

mesonbuild/dependencies/boost.py

@@ -209,7 +209,7 @@ class BoostDependency(ExternalDependency):
         for root in self.boost_roots:
             globtext = os.path.join(root, 'include', 'boost-*')
             incdirs = glob.glob(globtext)
-            if len(incdirs) > 0:
+            if incdirs:
                 return incdirs[0]
             incboostdir = os.path.join(root, 'include', 'boost')
             if os.path.isdir(incboostdir):
@@ -427,7 +427,7 @@ class BoostDependency(ExternalDependency):
         for entry in globber2_matches:
             fname = os.path.basename(entry)
             self.lib_modules[self.modname_from_filename(fname)] = [fname]
-        if len(globber2_matches) == 0:
+        if not globber2_matches:
             # FIXME - why are we only looking for *.lib? Mingw provides *.dll.a and *.a
             for entry in glob.glob(os.path.join(self.libdir, globber1 + '.lib')):
                 if self.static:

mesonbuild/mesonmain.py

@@ -110,7 +110,7 @@ class CommandLineParser:
         # If first arg is not a known command, assume user wants to run the setup
         # command.
         known_commands = list(self.commands.keys()) + ['-h', '--help']
-        if len(args) == 0 or args[0] not in known_commands:
+        if not args or args[0] not in known_commands:
             args = ['setup'] + args
 
         # Hidden commands have their own parser instead of using the global one

mesonbuild/minit.py

@@ -442,7 +442,7 @@ def add_arguments(parser):
     parser.add_argument('--version', default='0.1')
 
 def run(options):
-    if len(glob('*')) == 0:
+    if not glob('*'):
         autodetect_options(options, sample=True)
         if not options.language:
             print('Defaulting to generating a C language project.')

mesonbuild/mintro.py

@@ -343,7 +343,7 @@ def list_projinfo_from_source(sourcedir: str, intr: IntrospectionInterpreter):
     return intr.project_data
 
 def print_results(options, results, indent):
-    if len(results) == 0 and not options.force_dict:
+    if not results and not options.force_dict:
         print('No command specified')
         return 1
     elif len(results) == 1 and not options.force_dict:
@@ -487,7 +487,7 @@ def write_meson_info_file(builddata: build.Build, errors: list, build_files_upda
         'build_files_updated': build_files_updated,
     }
 
-    if len(errors) > 0:
+    if errors:
         info_data['error'] = True
         info_data['error_list'] = [x if isinstance(x, str) else str(x) for x in errors]
     else:

mesonbuild/modules/cmake.py

@@ -158,7 +158,7 @@ class CmakeModule(ExtensionModule):
 
     @permittedKwargs({'input', 'name', 'install_dir', 'configuration'})
     def configure_package_config_file(self, interpreter, state, args, kwargs):
-        if len(args) > 0:
+        if args:
             raise mesonlib.MesonException('configure_package_config_file takes only keyword arguments.')
 
         if 'input' not in kwargs:

mesonbuild/modules/qt.py

@@ -129,13 +129,13 @@ class QtBaseModule(ExtensionModule):
         self._detect_tools(state.environment, method)
         err_msg = "{0} sources specified and couldn't find {1}, " \
                   "please check your qt{2} installation"
-        if len(moc_headers) + len(moc_sources) > 0 and not self.moc.found():
+        if (moc_headers or moc_sources) and not self.moc.found():
             raise MesonException(err_msg.format('MOC', 'moc-qt{}'.format(self.qt_version), self.qt_version))
-        if len(rcc_files) > 0:
+        if rcc_files:
             if not self.rcc.found():
                 raise MesonException(err_msg.format('RCC', 'rcc-qt{}'.format(self.qt_version), self.qt_version))
             # custom output name set? -> one output file, multiple otherwise
-            if len(args) > 0:
+            if args:
                 qrc_deps = []
                 for i in rcc_files:
                     qrc_deps += self.parse_qrc(state, i)
@@ -160,7 +160,7 @@ class QtBaseModule(ExtensionModule):
                                   'depend_files': qrc_deps}
                     res_target = build.CustomTarget(name, state.subdir, state.subproject, rcc_kwargs)
                     sources.append(res_target)
-        if len(ui_files) > 0:
+        if ui_files:
             if not self.uic.found():
                 raise MesonException(err_msg.format('UIC', 'uic-qt{}'.format(self.qt_version), self.qt_version))
             arguments = uic_extra_arguments + ['-o', '@OUTPUT@', '@INPUT@']
@@ -183,14 +183,14 @@ class QtBaseModule(ExtensionModule):
                                      'either an external dependency (returned by find_library() or '
                                      'dependency()) or an internal dependency (returned by '
                                      'declare_dependency()).'.format(type(dep).__name__))
-        if len(moc_headers) > 0:
+        if moc_headers:
             arguments = moc_extra_arguments + inc + compile_args + ['@INPUT@', '-o', '@OUTPUT@']
             moc_kwargs = {'output': 'moc_@BASENAME@.cpp',
                           'arguments': arguments}
             moc_gen = build.Generator([self.moc], moc_kwargs)
             moc_output = moc_gen.process_files('Qt{} moc header'.format(self.qt_version), moc_headers, state)
             sources.append(moc_output)
-        if len(moc_sources) > 0:
+        if moc_sources:
             arguments = moc_extra_arguments + inc + compile_args + ['@INPUT@', '-o', '@OUTPUT@']
             moc_kwargs = {'output': '@BASENAME@.moc',
                           'arguments': arguments}

mesonbuild/modules/rpm.py

@@ -58,7 +58,7 @@ class RPMModule(ExtensionModule):
             elif isinstance(target, TypelibTarget) and target.should_install():
                 files.add('%%{_libdir}/girepository-1.0/%s' % target.get_filename()[0])
         for header in coredata.headers:
-            if len(header.get_install_subdir()) > 0:
+            if header.get_install_subdir():
                 files_devel.add('%%{_includedir}/%s/' % header.get_install_subdir())
             else:
                 for hdr_src in header.get_sources():
@@ -66,7 +66,7 @@ class RPMModule(ExtensionModule):
         for man in coredata.man:
             for man_file in man.get_sources():
                 files.add('%%{_mandir}/man%u/%s.*' % (int(man_file.split('.')[-1]), man_file))
-        if len(files_devel) > 0:
+        if files_devel:
             devel_subpkg = True
 
         filename = os.path.join(coredata.environment.get_build_dir(),
@@ -122,7 +122,7 @@ class RPMModule(ExtensionModule):
             fn.write('\n')
             fn.write('%install\n')
             fn.write('%meson_install\n')
-            if len(to_delete) > 0:
+            if to_delete:
                 fn.write('rm -vf %s\n' % ' '.join(to_delete))
             fn.write('\n')
             fn.write('%check\n')

mesonbuild/modules/unstable_icestorm.py

@@ -36,7 +36,7 @@ class IceStormModule(ExtensionModule):
     def project(self, interpreter, state, args, kwargs):
         if not self.yosys_bin:
             self.detect_binaries(interpreter)
-        if not len(args):
+        if not args:
             raise mesonlib.MesonException('Project requires at least one argument, which is the project name.')
         proj_name = args[0]
         arg_sources = args[1:]

mesonbuild/modules/unstable_simd.py

@@ -65,7 +65,7 @@ class SimdModule(ExtensionModule):
             if args is None:
                 mlog.log('Compiler supports %s:' % iset, mlog.red('NO'))
                 continue
-            if len(args) > 0:
+            if args:
                 if not compiler.has_multi_arguments(args, state.environment):
                     mlog.log('Compiler supports %s:' % iset, mlog.red('NO'))
                     continue

mesonbuild/scripts/dist.py

@@ -133,7 +133,7 @@ def create_dist_hg(dist_name, src_root, bld_root, dist_sub, dist_scripts):
     tarname = os.path.join(dist_sub, dist_name + '.tar')
     xzname = tarname + '.xz'
     subprocess.check_call(['hg', 'archive', '-R', src_root, '-S', '-t', 'tar', tarname])
-    if len(dist_scripts) > 0:
+    if dist_scripts:
         mlog.warning('dist scripts are not supported in Mercurial projects')
     with lzma.open(xzname, 'wb') as xf, open(tarname, 'rb') as tf:
         shutil.copyfileobj(tf, xf)

mesonbuild/scripts/gtkdochelper.py

@@ -175,7 +175,7 @@ def build_gtkdoc(source_root, build_root, doc_subdir, src_subdirs,
         mkdb_cmd.append('--name-space=' + namespace)
     if modeflag:
         mkdb_cmd.append(modeflag)
-    if len(main_file) > 0:
+    if main_file:
         # Yes, this is the flag even if the file is in xml.
         mkdb_cmd.append('--main-sgml-file=' + main_file)
     # Add user-specified arguments
@@ -187,7 +187,7 @@ def build_gtkdoc(source_root, build_root, doc_subdir, src_subdirs,
                   '--path=' + ':'.join((doc_src, abs_out)),
                   module,
                   ] + html_args
-    if len(main_file) > 0:
+    if main_file:
         mkhtml_cmd.append('../' + main_file)
     else:
         mkhtml_cmd.append('%s-docs.xml' % module)
@@ -212,23 +212,23 @@ def install_gtkdoc(build_root, doc_subdir, install_prefix, datadir, module):
 
 def run(args):
     options = parser.parse_args(args)
-    if len(options.htmlargs) > 0:
+    if options.htmlargs:
         htmlargs = options.htmlargs.split('@@')
     else:
         htmlargs = []
-    if len(options.scanargs) > 0:
+    if options.scanargs:
         scanargs = options.scanargs.split('@@')
     else:
         scanargs = []
-    if len(options.scanobjsargs) > 0:
+    if options.scanobjsargs:
         scanobjsargs = options.scanobjsargs.split('@@')
     else:
         scanobjsargs = []
-    if len(options.fixxrefargs) > 0:
+    if options.fixxrefargs:
         fixxrefargs = options.fixxrefargs.split('@@')
     else:
         fixxrefargs = []
-    if len(options.mkdbargs) > 0:
+    if options.mkdbargs:
         mkdbargs = options.mkdbargs.split('@@')
     else:
         mkdbargs = []

mesonbuild/scripts/meson_exe.py

@@ -60,7 +60,7 @@ def run_exe(exe):
             cmd = exe.fname
     child_env = os.environ.copy()
     child_env.update(exe.env)
-    if len(exe.extra_paths) > 0:
+    if exe.extra_paths:
         child_env['PATH'] = (os.pathsep.join(exe.extra_paths + ['']) +
                              child_env['PATH'])
         if exe.exe_runner and mesonlib.substring_is_in_list('wine', exe.exe_runner.get_command()):

mesonbuild/scripts/symbolextractor.py

@@ -69,7 +69,7 @@ def linux_syms(libfilename, outfilename):
     if pnm.returncode != 0:
         raise RuntimeError('nm does not work.')
     for line in output.split('\n'):
-        if len(line) == 0:
+        if not line:
             continue
         line_split = line.split()
         entry = line_split[0:2]
@@ -91,7 +91,7 @@ def osx_syms(libfilename, outfilename):
     pnm, output = Popen_safe(['nm', '-g', '-P', libfilename])[0:2]
     if pnm.returncode != 0:
         raise RuntimeError('nm does not work.')
-    result += [' '.join(x.split()[0:2]) for x in output.split('\n') if len(x) > 0 and not x.endswith('U')]
+    result += [' '.join(x.split()[0:2]) for x in output.split('\n') if x and not x.endswith('U')]
     write_if_changed('\n'.join(result) + '\n', outfilename)
 
 def gen_symbols(libfilename, outfilename, cross_host):