better message on script magic not found

More relevant now that we register default script magics that probably don't exist.

IPython/core/magics/script.py

@@ -1,275 +1,283 b''
 """Magic functions for running cells in various scripts."""
 #-----------------------------------------------------------------------------
 #  Copyright (c) 2012 The IPython Development Team.
 #
 #  Distributed under the terms of the Modified BSD License.
 #
 #  The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Stdlib
+import errno
 import os
 import re
 import sys
 import signal
 import time
 from subprocess import Popen, PIPE
 import atexit
 
 # Our own packages
 from IPython.config.configurable import Configurable
 from IPython.core import magic_arguments
 from IPython.core.error import UsageError
 from IPython.core.magic import  (
     Magics, magics_class, line_magic, cell_magic
 )
 from IPython.lib.backgroundjobs import BackgroundJobManager
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import py3compat
 from IPython.utils.process import arg_split
 from IPython.utils.traitlets import List, Dict
 
 #-----------------------------------------------------------------------------
 # Magic implementation classes
 #-----------------------------------------------------------------------------
 
 def script_args(f):
     """single decorator for adding script args"""
     args = [
         magic_arguments.argument(
             '--out', type=str,
             help="""The variable in which to store stdout from the script.
             If the script is backgrounded, this will be the stdout *pipe*,
             instead of the stderr text itself.
             """
         ),
         magic_arguments.argument(
             '--err', type=str,
             help="""The variable in which to store stderr from the script.
             If the script is backgrounded, this will be the stderr *pipe*,
             instead of the stderr text itself.
             """
         ),
         magic_arguments.argument(
             '--bg', action="store_true",
             help="""Whether to run the script in the background.
             If given, the only way to see the output of the command is
             with --out/err.
             """
         ),
         magic_arguments.argument(
             '--proc', type=str,
             help="""The variable in which to store Popen instance.
             This is used only when --bg option is given.
             """
         ),
     ]
     for arg in args:
         f = arg(f)
     return f
 
 @magics_class
 class ScriptMagics(Magics, Configurable):
     """Magics for talking to scripts
     
     This defines a base `%%script` cell magic for running a cell
     with a program in a subprocess, and registers a few top-level
     magics that call %%script with common interpreters.
     """
     script_magics = List(config=True,
         help="""Extra script cell magics to define
         
         This generates simple wrappers of `%%script foo` as `%%foo`.
         
         If you want to add script magics that aren't on your path,
         specify them in script_paths
         """,
     )
     def _script_magics_default(self):
         """default to a common list of programs"""
         
         defaults = [
             'sh',
             'bash',
             'perl',
             'ruby',
             'python',
             'python3',
             'pypy',
         ]
         if os.name == 'nt':
             defaults.extend([
                 'cmd',
                 'powershell',
             ])
         
         return defaults
     
     script_paths = Dict(config=True,
         help="""Dict mapping short 'ruby' names to full paths, such as '/opt/secret/bin/ruby'
         
         Only necessary for items in script_magics where the default path will not
         find the right interpreter.
         """
     )
     
     def __init__(self, shell=None):
         Configurable.__init__(self, config=shell.config)
         self._generate_script_magics()
         Magics.__init__(self, shell=shell)
         self.job_manager = BackgroundJobManager()
         self.bg_processes = []
         atexit.register(self.kill_bg_processes)
 
     def __del__(self):
         self.kill_bg_processes()
     
     def _generate_script_magics(self):
         cell_magics = self.magics['cell']
         for name in self.script_magics:
             cell_magics[name] = self._make_script_magic(name)
     
     def _make_script_magic(self, name):
         """make a named magic, that calls %%script with a particular program"""
         # expand to explicit path if necessary:
         script = self.script_paths.get(name, name)
         
         @magic_arguments.magic_arguments()
         @script_args
         def named_script_magic(line, cell):
             # if line, add it as cl-flags
             if line:
                  line = "%s %s" % (script, line)
             else:
                 line = script
             return self.shebang(line, cell)
         
         # write a basic docstring:
         named_script_magic.__doc__ = \
         """%%{name} script magic
         
         Run cells with {script} in a subprocess.
         
         This is a shortcut for `%%script {script}`
         """.format(**locals())
         
         return named_script_magic
     
     @magic_arguments.magic_arguments()
     @script_args
     @cell_magic("script")
     def shebang(self, line, cell):
         """Run a cell via a shell command
         
         The `%%script` line is like the #! line of script,
         specifying a program (bash, perl, ruby, etc.) with which to run.
         
         The rest of the cell is run by that program.
         
         Examples
         --------
         ::
         
             In [1]: %%script bash
                ...: for i in 1 2 3; do
                ...:   echo $i
                ...: done
             1
             2
             3
         """
         argv = arg_split(line, posix = not sys.platform.startswith('win'))
         args, cmd = self.shebang.parser.parse_known_args(argv)
 
+        try:
         p = Popen(cmd, stdout=PIPE, stderr=PIPE, stdin=PIPE)
+        except OSError as e:
+            if e.errno == errno.ENOENT:
+                print "Couldn't find program: %r" % cmd[0]
+                return
+            else:
+                raise
         
         cell = cell.encode('utf8', 'replace')
         if args.bg:
             self.bg_processes.append(p)
             self._gc_bg_processes()
             if args.out:
                 self.shell.user_ns[args.out] = p.stdout
             if args.err:
                 self.shell.user_ns[args.err] = p.stderr
             self.job_manager.new(self._run_script, p, cell, daemon=True)
             if args.proc:
                 self.shell.user_ns[args.proc] = p
             return
         
         try:
             out, err = p.communicate(cell)
         except KeyboardInterrupt:
             try:
                 p.send_signal(signal.SIGINT)
                 time.sleep(0.1)
                 if p.poll() is not None:
                     print "Process is interrupted."
                     return
                 p.terminate()
                 time.sleep(0.1)
                 if p.poll() is not None:
                     print "Process is terminated."
                     return
                 p.kill()
                 print "Process is killed."
             except OSError:
                 pass
             except Exception as e:
                 print "Error while terminating subprocess (pid=%i): %s" \
                     % (p.pid, e)
             return
         out = py3compat.bytes_to_str(out)
         err = py3compat.bytes_to_str(err)
         if args.out:
             self.shell.user_ns[args.out] = out
         else:
             sys.stdout.write(out)
             sys.stdout.flush()
         if args.err:
             self.shell.user_ns[args.err] = err
         else:
             sys.stderr.write(err)
             sys.stderr.flush()
     
     def _run_script(self, p, cell):
         """callback for running the script in the background"""
         p.stdin.write(cell)
         p.stdin.close()
         p.wait()
 
     @line_magic("killbgscripts")
     def killbgscripts(self, _nouse_=''):
         """Kill all BG processes started by %%script and its family."""
         self.kill_bg_processes()
         print "All background processes were killed."
 
     def kill_bg_processes(self):
         """Kill all BG processes which are still running."""
         for p in self.bg_processes:
             if p.poll() is None:
                 try:
                     p.send_signal(signal.SIGINT)
                 except:
                     pass
         time.sleep(0.1)
         for p in self.bg_processes:
             if p.poll() is None:
                 try:
                     p.terminate()
                 except:
                     pass
         time.sleep(0.1)
         for p in self.bg_processes:
             if p.poll() is None:
                 try:
                     p.kill()
                 except:
                     pass
         self._gc_bg_processes()
 
     def _gc_bg_processes(self):
         self.bg_processes = [p for p in self.bg_processes if p.poll() is None]