[Webkit-unassigned] [Bug 229824] New: [webkitpy] WrappedPopen breaks process returncode

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=229824

            Bug ID: 229824
           Summary: [webkitpy] WrappedPopen breaks process returncode
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Tools / Tests
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: clopez at igalia.com
                CC: jbedard at apple.com

The class WrappedPopen() was added in r250375 to wrap the subprocess.Popen() for making the python2 subprocess.Popen() objects more similar to the ones from python3.

But the way this class wraps the objects makes breaks the process returncode if the process doesn't return immediately.

This is because WrappedPopen() defines a new class the sets functions with the same name than subprocess.Popen() setting the value returned to the one that returns subprocess.Popen().
But in the case of subprocess.Popen().returncode that is not a function, but a string that will change of value when the process ends. If we evaluate this function before we call subprocess.Popen().communicate() or subprocess.Popen().wait() then the value of returncode will be None

This can be checked with this following test program: http://sprunge.us/aoxZ0j

If you run it with python2 you get "The call return code is None" instead of getting "The call return code is 2" which is what it should be (what happens when you run it with python3 which don't triggers the call to use WrappedPopen())

I have observed this when working on bug 229758 .. with python2 the call from host.executive.popen() always returned a returncode of None

This is not an issue for subprocess.Popen().stdout and subprocess.Popen().stderr because if you look at what prints the debug function on that example for this cases it sets the value to a descriptor rather than reading from the descriptor. So when the call to read from the descriptor is done it will work. Example, you see this:

setting attribute .. stdout to <open file '<fdopen>', mode 'rb' at 0x7fe12cc1d540>
setting attribute .. returncode to None

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