- Small fix to pexpect to prevent unhandled exceptions at Python shutdown

  time.

IPython/irunner.py

@@ -1,360 +1,395 b''
 #!/usr/bin/env python
 """Module for interactively running scripts.
 
 This module implements classes for interactively running scripts written for
 any system with a prompt which can be matched by a regexp suitable for
 pexpect.  It can be used to run as if they had been typed up interactively, an
 arbitrary series of commands for the target system.
 
 The module includes classes ready for IPython (with the default prompts),
 plain Python and SAGE, but making a new one is trivial.  To see how to use it,
 simply run the module as a script:
 
 ./irunner.py --help
 
 
 This is an extension of Ken Schutte <kschutte-AT-csail.mit.edu>'s script
 contributed on the ipython-user list:
 
 http://scipy.net/pipermail/ipython-user/2006-May/001705.html
 
 
 NOTES:
 
  - This module requires pexpect, available in most linux distros, or which can
  be downloaded from
 
     http://pexpect.sourceforge.net
 
  - Because pexpect only works under Unix or Windows-Cygwin, this has the same
  limitations.  This means that it will NOT work under native windows Python.
 """
 
 # Stdlib imports
 import optparse
 import os
 import sys
 
 # Third-party modules.
 import pexpect
 
 # Global usage strings, to avoid indentation issues when typing it below.
 USAGE = """
 Interactive script runner, type: %s
 
 runner [opts] script_name
 """
 
+def pexpect_monkeypatch():
+    """Patch pexpect to prevent unhandled exceptions at VM teardown.
+
+    Calling this function will monkeypatch the pexpect.spawn class and modify
+    its __del__ method to make it more robust in the face of failures that can
+    occur if it is called when the Python VM is shutting down.
+
+    Since Python may fire __del__ methods arbitrarily late, it's possible for
+    them to execute during the teardown of the Python VM itself.  At this
+    point, various builtin modules have been reset to None.  Thus, the call to
+    self.close() will trigger an exception because it tries to call os.close(),
+    and os is now None.
+    """
+    
+    if pexpect.__version__[:3] >= '2.2':
+        # No need to patch, fix is already the upstream version.
+        return
+    
+    def __del__(self):
+        """This makes sure that no system resources are left open.
+        Python only garbage collects Python objects. OS file descriptors
+        are not Python objects, so they must be handled explicitly.
+        If the child file descriptor was opened outside of this class
+        (passed to the constructor) then this does not close it.
+        """
+        if not self.closed:
+            try:
+                self.close()
+            except AttributeError:
+                pass
+
+    pexpect.spawn.__del__ = __del__
+
+pexpect_monkeypatch()
+
 # The generic runner class
 class InteractiveRunner(object):
     """Class to run a sequence of commands through an interactive program."""
     
     def __init__(self,program,prompts,args=None,out=sys.stdout,echo=True):
         """Construct a runner.
 
         Inputs:
 
           - program: command to execute the given program.
 
           - prompts: a list of patterns to match as valid prompts, in the
           format used by pexpect.  This basically means that it can be either
           a string (to be compiled as a regular expression) or a list of such
           (it must be a true list, as pexpect does type checks).
 
           If more than one prompt is given, the first is treated as the main
           program prompt and the others as 'continuation' prompts, like
           python's.  This means that blank lines in the input source are
           ommitted when the first prompt is matched, but are NOT ommitted when
           the continuation one matches, since this is how python signals the
           end of multiline input interactively.
 
         Optional inputs:
 
           - args(None): optional list of strings to pass as arguments to the
           child program.
 
           - out(sys.stdout): if given, an output stream to be used when writing
           output.  The only requirement is that it must have a .write() method.
 
         Public members not parameterized in the constructor:
 
           - delaybeforesend(0): Newer versions of pexpect have a delay before
           sending each new input.  For our purposes here, it's typically best
           to just set this to zero, but if you encounter reliability problems
           or want an interactive run to pause briefly at each prompt, just
           increase this value (it is measured in seconds).  Note that this
           variable is not honored at all by older versions of pexpect.
         """
         
         self.program = program
         self.prompts = prompts
         if args is None: args = []
         self.args = args
         self.out = out
         self.echo = echo
         # Other public members which we don't make as parameters, but which
         # users may occasionally want to tweak
         self.delaybeforesend = 0
 
         # Create child process and hold on to it so we don't have to re-create
         # for every single execution call
         c = self.child = pexpect.spawn(self.program,self.args,timeout=None)
         c.delaybeforesend = self.delaybeforesend
         # pexpect hard-codes the terminal size as (24,80) (rows,columns).
         # This causes problems because any line longer than 80 characters gets
         # completely overwrapped on the printed outptut (even though
         # internally the code runs fine).  We reset this to 99 rows X 200
         # columns (arbitrarily chosen), which should avoid problems in all
         # reasonable cases.
         c.setwinsize(99,200)
 
     def close(self):
         """close child process"""
 
         self.child.close()
 
     def run_file(self,fname,interact=False,get_output=False):
         """Run the given file interactively.
 
         Inputs:
 
           -fname: name of the file to execute.
 
         See the run_source docstring for the meaning of the optional
         arguments."""
 
         fobj = open(fname,'r')
         try:
             out = self.run_source(fobj,interact,get_output)
         finally:
             fobj.close()
         if get_output:
             return out
 
     def run_source(self,source,interact=False,get_output=False):
         """Run the given source code interactively.
 
         Inputs:
 
           - source: a string of code to be executed, or an open file object we
           can iterate over.
 
         Optional inputs:
 
           - interact(False): if true, start to interact with the running
           program at the end of the script.  Otherwise, just exit.
 
           - get_output(False): if true, capture the output of the child process
           (filtering the input commands out) and return it as a string.
 
         Returns:
           A string containing the process output, but only if requested.
           """
 
         # if the source is a string, chop it up in lines so we can iterate
         # over it just as if it were an open file.
         if not isinstance(source,file):
             source = source.splitlines(True)
 
         if self.echo:
             # normalize all strings we write to use the native OS line
             # separators.
             linesep  = os.linesep
             stdwrite = self.out.write
             write    = lambda s: stdwrite(s.replace('\r\n',linesep))
         else:
             # Quiet mode, all writes are no-ops
             write = lambda s: None
             
         c = self.child
         prompts = c.compile_pattern_list(self.prompts)
         prompt_idx = c.expect_list(prompts)
 
         # Flag whether the script ends normally or not, to know whether we can
         # do anything further with the underlying process.
         end_normal = True
 
         # If the output was requested, store it in a list for return at the end
         if get_output:
             output = []
             store_output = output.append
         
         for cmd in source:
             # skip blank lines for all matches to the 'main' prompt, while the
             # secondary prompts do not
             if prompt_idx==0 and \
                    (cmd.isspace() or cmd.lstrip().startswith('#')):
                 write(cmd)
                 continue
 
             #write('AFTER: '+c.after)  # dbg
             write(c.after)
             c.send(cmd)
             try:
                 prompt_idx = c.expect_list(prompts)
             except pexpect.EOF:
                 # this will happen if the child dies unexpectedly
                 write(c.before)
                 end_normal = False
                 break
             
             write(c.before)
 
             # With an echoing process, the output we get in c.before contains
             # the command sent, a newline, and then the actual process output
             if get_output:
                 store_output(c.before[len(cmd+'\n'):])
                 #write('CMD: <<%s>>' % cmd)  # dbg
                 #write('OUTPUT: <<%s>>' % output[-1])  # dbg
 
         self.out.flush()
         if end_normal:
             if interact:
                 c.send('\n')
                 print '<< Starting interactive mode >>',
                 try:
                     c.interact()
                 except OSError:
                     # This is what fires when the child stops.  Simply print a
                     # newline so the system prompt is aligned.  The extra
                     # space is there to make sure it gets printed, otherwise
                     # OS buffering sometimes just suppresses it.
                     write(' \n')
                     self.out.flush()
         else:
             if interact:
                 e="Further interaction is not possible: child process is dead."
                 print >> sys.stderr, e
 
         # Leave the child ready for more input later on, otherwise select just
         # hangs on the second invocation.
         c.send('\n')
         
         # Return any requested output
         if get_output:
             return ''.join(output)
                 
     def main(self,argv=None):
         """Run as a command-line script."""
 
         parser = optparse.OptionParser(usage=USAGE % self.__class__.__name__)
         newopt = parser.add_option
         newopt('-i','--interact',action='store_true',default=False,
                help='Interact with the program after the script is run.')
 
         opts,args = parser.parse_args(argv)
 
         if len(args) != 1:
             print >> sys.stderr,"You must supply exactly one file to run."
             sys.exit(1)
 
         self.run_file(args[0],opts.interact)
 
 
 # Specific runners for particular programs
 class IPythonRunner(InteractiveRunner):
     """Interactive IPython runner.
 
     This initalizes IPython in 'nocolor' mode for simplicity.  This lets us
     avoid having to write a regexp that matches ANSI sequences, though pexpect
     does support them.  If anyone contributes patches for ANSI color support,
     they will be welcome.
 
     It also sets the prompts manually, since the prompt regexps for
     pexpect need to be matched to the actual prompts, so user-customized
     prompts would break this.
     """
     
     def __init__(self,program = 'ipython',args=None,out=sys.stdout,echo=True):
         """New runner, optionally passing the ipython command to use."""
         
         args0 = ['-colors','NoColor',
                  '-pi1','In [\\#]: ',
                  '-pi2','   .\\D.: ',
                  '-noterm_title',
                  '-noautoindent']
         if args is None: args = args0
         else: args = args0 + args
         prompts = [r'In \[\d+\]: ',r'   \.*: ']
         InteractiveRunner.__init__(self,program,prompts,args,out,echo)
 
 
 class PythonRunner(InteractiveRunner):
     """Interactive Python runner."""
 
     def __init__(self,program='python',args=None,out=sys.stdout,echo=True):
         """New runner, optionally passing the python command to use."""
 
         prompts = [r'>>> ',r'\.\.\. ']
         InteractiveRunner.__init__(self,program,prompts,args,out,echo)
 
 
 class SAGERunner(InteractiveRunner):
     """Interactive SAGE runner.
     
     WARNING: this runner only works if you manually configure your SAGE copy
     to use 'colors NoColor' in the ipythonrc config file, since currently the
     prompt matching regexp does not identify color sequences."""
 
     def __init__(self,program='sage',args=None,out=sys.stdout,echo=True):
         """New runner, optionally passing the sage command to use."""
 
         prompts = ['sage: ',r'\s*\.\.\. ']
         InteractiveRunner.__init__(self,program,prompts,args,out,echo)
 
 # Global usage string, to avoid indentation issues if typed in a function def.
 MAIN_USAGE = """
 %prog [options] file_to_run
 
 This is an interface to the various interactive runners available in this
 module.  If you want to pass specific options to one of the runners, you need
 to first terminate the main options with a '--', and then provide the runner's
 options.  For example:
 
 irunner.py --python -- --help
 
 will pass --help to the python runner.  Similarly,
 
 irunner.py --ipython -- --interact script.ipy
 
 will run the script.ipy file under the IPython runner, and then will start to
 interact with IPython at the end of the script (instead of exiting).
 
 The already implemented runners are listed below; adding one for a new program
 is a trivial task, see the source for examples.
 
 WARNING: the SAGE runner only works if you manually configure your SAGE copy
 to use 'colors NoColor' in the ipythonrc config file, since currently the
 prompt matching regexp does not identify color sequences.
 """
 
 def main():
     """Run as a command-line script."""
 
     parser = optparse.OptionParser(usage=MAIN_USAGE)
     newopt = parser.add_option
     parser.set_defaults(mode='ipython')
     newopt('--ipython',action='store_const',dest='mode',const='ipython',
            help='IPython interactive runner (default).')
     newopt('--python',action='store_const',dest='mode',const='python',
            help='Python interactive runner.')
     newopt('--sage',action='store_const',dest='mode',const='sage',
            help='SAGE interactive runner.')
 
     opts,args = parser.parse_args()
     runners = dict(ipython=IPythonRunner,
                    python=PythonRunner,
                    sage=SAGERunner)
 
     try:
         ext = os.path.splitext(args[0])[-1]
     except IndexError:
         ext = ''
     modes = {'.ipy':'ipython',
              '.py':'python',
              '.sage':'sage'}
     mode = modes.get(ext,opts.mode)
     runners[mode]().main(args)
 
 if __name__ == '__main__':
     main()