Source

pylib-hacks / py / _io / capture.py

The branch 'trunk' does not exist.
Full commit
import os
import sys
import py
import tempfile

try:
    from io import StringIO
except ImportError:
    from StringIO import StringIO

if sys.version_info < (3,0):
    class TextIO(StringIO):
        def write(self, data):
            if not isinstance(data, unicode):
                data = unicode(data, getattr(self, '_encoding', 'UTF-8'))
            StringIO.write(self, data)
else:
    TextIO = StringIO

try:
    from io import BytesIO
except ImportError:
    class BytesIO(StringIO):
        def write(self, data):
            if isinstance(data, unicode):
                raise TypeError("not a byte value: %r" %(data,))
            StringIO.write(self, data)

patchsysdict = {0: 'stdin', 1: 'stdout', 2: 'stderr'}

class FDCapture:
    """ Capture IO to/from a given os-level filedescriptor. """

    def __init__(self, targetfd, tmpfile=None, now=True, patchsys=False):
        """ save targetfd descriptor, and open a new
            temporary file there.  If no tmpfile is
            specified a tempfile.Tempfile() will be opened
            in text mode.
        """
        self.targetfd = targetfd
        if tmpfile is None and targetfd != 0:
            f = tempfile.TemporaryFile('wb+')
            tmpfile = dupfile(f, encoding="UTF-8")
            f.close()
        self.tmpfile = tmpfile
        self._savefd = os.dup(self.targetfd)
        if patchsys:
            self._oldsys = getattr(sys, patchsysdict[targetfd])
        if now:
            self.start()

    def start(self):
        try:
            os.fstat(self._savefd)
        except OSError:
            raise ValueError("saved filedescriptor not valid, "
                "did you call start() twice?")
        if self.targetfd == 0 and not self.tmpfile:
            fd = os.open(devnullpath, os.O_RDONLY)
            os.dup2(fd, 0)
            os.close(fd)
            if hasattr(self, '_oldsys'):
                setattr(sys, patchsysdict[self.targetfd], DontReadFromInput())
        else:
            os.dup2(self.tmpfile.fileno(), self.targetfd)
            if hasattr(self, '_oldsys'):
                setattr(sys, patchsysdict[self.targetfd], self.tmpfile)

    def done(self):
        """ unpatch and clean up, returns the self.tmpfile (file object)
        """
        os.dup2(self._savefd, self.targetfd)
        os.close(self._savefd)
        if self.targetfd != 0:
            self.tmpfile.seek(0)
        if hasattr(self, '_oldsys'):
            setattr(sys, patchsysdict[self.targetfd], self._oldsys)
        return self.tmpfile

    def writeorg(self, data):
        """ write a string to the original file descriptor
        """
        tempfp = tempfile.TemporaryFile()
        try:
            os.dup2(self._savefd, tempfp.fileno())
            tempfp.write(data)
        finally:
            tempfp.close()


def dupfile(f, mode=None, buffering=0, raising=False, encoding=None):
    """ return a new open file object that's a duplicate of f

        mode is duplicated if not given, 'buffering' controls
        buffer size (defaulting to no buffering) and 'raising'
        defines whether an exception is raised when an incompatible
        file object is passed in (if raising is False, the file
        object itself will be returned)
    """
    try:
        fd = f.fileno()
    except AttributeError:
        if raising:
            raise
        return f
    newfd = os.dup(fd)
    mode = mode and mode or f.mode
    if sys.version_info >= (3,0):
        if encoding is not None:
            mode = mode.replace("b", "")
            buffering = True
        return os.fdopen(newfd, mode, buffering, encoding, closefd=True)
    else:
        f = os.fdopen(newfd, mode, buffering)
        if encoding is not None:
            return EncodedFile(f, encoding)
        return f

class EncodedFile(object):
    def __init__(self, _stream, encoding):
        self._stream = _stream
        self.encoding = encoding

    def write(self, obj):
        if isinstance(obj, unicode):
            obj = obj.encode(self.encoding)
        elif isinstance(obj, str):
            pass
        else:
            obj = str(obj)
        self._stream.write(obj)

    def writelines(self, linelist):
        data = ''.join(linelist)
        self.write(data)

    def __getattr__(self, name):
        return getattr(self._stream, name)

class Capture(object):
    def call(cls, func, *args, **kwargs):
        """ return a (res, out, err) tuple where
            out and err represent the output/error output
            during function execution.
            call the given function with args/kwargs
            and capture output/error during its execution.
        """
        so = cls()
        try:
            res = func(*args, **kwargs)
        finally:
            out, err = so.reset()
        return res, out, err
    call = classmethod(call)

    def reset(self):
        """ reset sys.stdout/stderr and return captured output as strings. """
        if hasattr(self, '_reset'):
            raise ValueError("was already reset")
        self._reset = True
        outfile, errfile = self.done(save=False)
        out, err = "", ""
        if outfile and not outfile.closed:
            out = outfile.read()
            outfile.close()
        if errfile and errfile != outfile and not errfile.closed:
            err = errfile.read()
            errfile.close()
        return out, err

    def suspend(self):
        """ return current snapshot captures, memorize tempfiles. """
        outerr = self.readouterr()
        outfile, errfile = self.done()
        return outerr


class StdCaptureFD(Capture):
    """ This class allows to capture writes to FD1 and FD2
        and may connect a NULL file to FD0 (and prevent
        reads from sys.stdin).  If any of the 0,1,2 file descriptors
        is invalid it will not be captured.
    """
    def __init__(self, out=True, err=True, mixed=False,
        in_=True, patchsys=True, now=True):
        self._options = locals()
        self._save()
        if now:
            self.startall()

    def _save(self):
        in_ = self._options['in_']
        out = self._options['out']
        err = self._options['err']
        mixed = self._options['mixed']
        patchsys = self._options['patchsys']
        if in_:
            try:
                self.in_ = FDCapture(0, tmpfile=None, now=False,
                    patchsys=patchsys)
            except OSError:
                pass
        if out:
            tmpfile = None
            if hasattr(out, 'write'):
                tmpfile = out
            try:
                self.out = FDCapture(1, tmpfile=tmpfile,
                           now=False, patchsys=patchsys)
                self._options['out'] = self.out.tmpfile
            except OSError:
                pass
        if err:
            if out and mixed:
                tmpfile = self.out.tmpfile
            elif hasattr(err, 'write'):
                tmpfile = err
            else:
                tmpfile = None
            try:
                self.err = FDCapture(2, tmpfile=tmpfile,
                           now=False, patchsys=patchsys)
                self._options['err'] = self.err.tmpfile
            except OSError:
                pass

    def startall(self):
        if hasattr(self, 'in_'):
            self.in_.start()
        if hasattr(self, 'out'):
            self.out.start()
        if hasattr(self, 'err'):
            self.err.start()

    def resume(self):
        """ resume capturing with original temp files. """
        self.startall()

    def done(self, save=True):
        """ return (outfile, errfile) and stop capturing. """
        outfile = errfile = None
        if hasattr(self, 'out') and not self.out.tmpfile.closed:
            outfile = self.out.done()
        if hasattr(self, 'err') and not self.err.tmpfile.closed:
            errfile = self.err.done()
        if hasattr(self, 'in_'):
            tmpfile = self.in_.done()
        if save:
            self._save()
        return outfile, errfile

    def readouterr(self):
        """ return snapshot value of stdout/stderr capturings. """
        l = []
        for name in ('out', 'err'):
            res = ""
            if hasattr(self, name):
                f = getattr(self, name).tmpfile
                f.seek(0)
                res = f.read()
                f.truncate(0)
                f.seek(0)
            l.append(res)
        return l

class StdCapture(Capture):
    """ This class allows to capture writes to sys.stdout|stderr "in-memory"
        and will raise errors on tries to read from sys.stdin. It only
        modifies sys.stdout|stderr|stdin attributes and does not
        touch underlying File Descriptors (use StdCaptureFD for that).
    """
    def __init__(self, out=True, err=True, in_=True, mixed=False, now=True):
        self._oldout = sys.stdout
        self._olderr = sys.stderr
        self._oldin  = sys.stdin
        if out and not hasattr(out, 'file'):
            out = TextIO()
        self.out = out
        if err:
            if mixed:
                err = out
            elif not hasattr(err, 'write'):
                err = TextIO()
        self.err = err
        self.in_ = in_
        if now:
            self.startall()

    def startall(self):
        if self.out:
            sys.stdout = self.out
        if self.err:
            sys.stderr = self.err
        if self.in_:
            sys.stdin  = self.in_  = DontReadFromInput()

    def done(self, save=True):
        """ return (outfile, errfile) and stop capturing. """
        outfile = errfile = None
        if self.out and not self.out.closed:
            sys.stdout = self._oldout
            outfile = self.out
            outfile.seek(0)
        if self.err and not self.err.closed:
            sys.stderr = self._olderr
            errfile = self.err
            errfile.seek(0)
        if self.in_:
            sys.stdin = self._oldin
        return outfile, errfile

    def resume(self):
        """ resume capturing with original temp files. """
        self.startall()

    def readouterr(self):
        """ return snapshot value of stdout/stderr capturings. """
        out = err = ""
        if self.out:
            out = self.out.getvalue()
            self.out.truncate(0)
            self.out.seek(0)
        if self.err:
            err = self.err.getvalue()
            self.err.truncate(0)
            self.err.seek(0)
        return out, err

class DontReadFromInput:
    """Temporary stub class.  Ideally when stdin is accessed, the
    capturing should be turned off, with possibly all data captured
    so far sent to the screen.  This should be configurable, though,
    because in automated test runs it is better to crash than
    hang indefinitely.
    """
    def read(self, *args):
        raise IOError("reading from stdin while output is captured")
    readline = read
    readlines = read
    __iter__ = read

    def fileno(self):
        raise ValueError("redirected Stdin is pseudofile, has no fileno()")
    def isatty(self):
        return False
    def close(self):
        pass

try:
    devnullpath = os.devnull
except AttributeError:
    if os.name == 'nt':
        devnullpath = 'NUL'
    else:
        devnullpath = '/dev/null'