Popovich/clcache — comment on commit e78bd63b31cf32e2569cf95788bf5962846e23e9
File:  line 0
By Popovich:

Yes, visual studio by default passed a directory.

For example, here is a compiler options from Visual Studio project debug configuration:
/Od /D "WIN32" /D "_DEBUG" /D "_CONSOLE" /D "_UNICODE" /D "UNICODE" /FD /EHsc /RTC1 /MDd /Fo"Debug\\" /Fd"Debug\\" /W3 /nologo /c /ZI /TP /errorReport:prompt
/Fo option value is "Debug\"

And also msdn says: /Fo (Object File Name) specifies an object (.obj) file name or directory to be used instead of the default.

And about os.path.isfile(). You are right! It's a stupid mistake :) We need to check is outputFile is a valid file name or directory name.