[lit] Compare to None using identity, not equality

[modocache]

Summary

In Python, None is a singleton, so checking whether a variable is
None may be done with is or is not. This has a slight advantage
over equiality comparisons == None and != None, since __eq__ may
be overridden in Python to produce sometimes unexpected results.

Using is None and is not None is also recommended practice in
https://www.python.org/dev/peps/pep-0008:

Comparisons to singletons like None should always be done with is or
is not, never the equality operators.

[beanz]

LGTM!

[modocache]

Thanks! I'll need you or someone else to commit for me. :)

[beanz]

Committed in rL283088. Thanks for the patch!

[modocache]

Thanks!

utils/lit/lit/TestRunner.py

for i,(out,err) in enumerate(procData):
         if res != 0:
             for (name, mode, f, path) in sorted(opened_files):
                 if path is not None and mode in ('w', 'a'):
                     try:
                         with open(path, 'rb') as f:
                             data = f.read()
                     except:
                         data = None
-                    if data != None:
+                    if data is not None:
                         output_files.append((name, path, data))
             
         results.append(ShellCommandResult(
             cmd.commands[i], out, err, res, timeoutHelper.timeoutReached(),
             output_files))
         if cmd.pipe_err:
             # Python treats the exit code as a signed char.
             if exitCode is None:
else:
         res = executeScriptInternal(test, litConfig, tmpBase, script, execdir)
     if isinstance(res, lit.Test.Result):
         return res
 
     out,err,exitCode,timeoutInfo = res
     if exitCode == 0:
         status = Test.PASS
     else:
-        if timeoutInfo == None:
+        if timeoutInfo is None:
             status = Test.FAIL
         else:
             status = Test.TIMEOUT
 
     # Form the output log.
     output = """Script:\n--\n%s\n--\nExit Code: %d\n""" % (
         '\n'.join(script), exitCode)
 
-    if timeoutInfo != None:
+    if timeoutInfo is not None:
         output += """Timeout: %s\n""" % (timeoutInfo,)
     output += "\n"
 
     # Append the outputs, if present.
     if out:
         output += """Command Output (stdout):\n--\n%s\n--\n""" % (out,)
     if err:
         output += """Command Output (stderr):\n--\n%s\n--\n""" % (err,)

utils/lit/lit/main.py

# threads by default there.
     for entry in opts.userParameters:
         if '=' not in entry:
             name,val = entry,''
         else:
             name,val = entry.split('=', 1)
         userParams[name] = val
 
     # Decide what the requested maximum indvidual test time should be
-    if opts.maxIndividualTestTime != None:
+    if opts.maxIndividualTestTime is not None:
         maxIndividualTestTime = opts.maxIndividualTestTime
     else:
         # Default is zero
         maxIndividualTestTime = 0
 
     isWindows = platform.system() == 'Windows'
 
     # Create the global config object.
# threads by default there.
 
     # Perform test discovery.
     run = lit.run.Run(litConfig,
                       lit.discovery.find_tests_for_inputs(litConfig, inputs))
 
     # After test discovery the configuration might have changed
     # the maxIndividualTestTime. If we explicitly set this on the
     # command line then override what was set in the test configuration
-    if opts.maxIndividualTestTime != None:
+    if opts.maxIndividualTestTime is not None:
         if opts.maxIndividualTestTime != litConfig.maxIndividualTestTime:
             litConfig.note(('The test suite configuration requested an individual'
                 ' test timeout of {0} seconds but a timeout of {1} seconds was'
                 ' requested on the command line. Forcing timeout to be {1}'
                 ' seconds')
                 .format(litConfig.maxIndividualTestTime,
                         opts.maxIndividualTestTime))
             litConfig.maxIndividualTestTime = opts.maxIndividualTestTime