Clean up and document better starting process of global IPython in tests.

IPython/testing/globalipapp.py

@@ -1,160 +1,168 b''
 """Global IPython app to support test running.
 
 We must start our own ipython object and heavily muck with it so that all the
 modifications IPython makes to system behavior don't send the doctest machinery
 into a fit.  This code should be considered a gross hack, but it gets the job
 done.
 """
 
 from __future__ import absolute_import
 
 #-----------------------------------------------------------------------------
 # Module imports
 #-----------------------------------------------------------------------------
 
 # From the standard library
 import __builtin__
 import commands
 import new
 import os
 import sys
 
 from . import tools
 from IPython.utils.genutils import Term
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 
 # Hack to modify the %run command so we can sync the user's namespace with the
 # test globals.  Once we move over to a clean magic system, this will be done
 # with much less ugliness.
 
 class py_file_finder(object):
     def __init__(self,test_filename):
         self.test_filename = test_filename
         
     def __call__(self,name):
         from IPython.utils.genutils import get_py_filename
         try:
             return get_py_filename(name)
         except IOError:
             test_dir = os.path.dirname(self.test_filename)
             new_path = os.path.join(test_dir,name)
             return get_py_filename(new_path)
     
 
 def _run_ns_sync(self,arg_s,runner=None):
     """Modified version of %run that syncs testing namespaces.
 
     This is strictly needed for running doctests that call %run.
     """
     #print >> sys.stderr,  'in run_ns_sync', arg_s  # dbg
     
     _ip = get_ipython()
     finder = py_file_finder(arg_s)
     out = _ip.magic_run_ori(arg_s,runner,finder)
     return out
 
 
 class ipnsdict(dict):
     """A special subclass of dict for use as an IPython namespace in doctests.
 
     This subclass adds a simple checkpointing capability so that when testing
     machinery clears it (we use it as the test execution context), it doesn't
     get completely destroyed.
     """
     
     def __init__(self,*a):
         dict.__init__(self,*a)
         self._savedict = {}
         
     def clear(self):
         dict.clear(self)
         self.update(self._savedict)
-
+        
     def _checkpoint(self):
         self._savedict.clear()
         self._savedict.update(self)
 
     def update(self,other):
         self._checkpoint()
         dict.update(self,other)
 
         # If '_' is in the namespace, python won't set it when executing code,
         # and we have examples that test it.  So we ensure that the namespace
         # is always 'clean' of it before it's used for test code execution.
         self.pop('_',None)
 
         # The builtins namespace must *always* be the real __builtin__ module,
         # else weird stuff happens.  The main ipython code does have provisions
         # to ensure this after %run, but since in this class we do some
         # aggressive low-level cleaning of the execution namespace, we need to
         # correct for that ourselves, to ensure consitency with the 'real'
         # ipython.
         self['__builtins__'] = __builtin__
         
 
 def get_ipython():
     # This will get replaced by the real thing once we start IPython below
     return start_ipython()
 
 def start_ipython():
     """Start a global IPython shell, which we need for IPython-specific syntax.
     """
     global get_ipython
 
     # This function should only ever run once!
     if hasattr(start_ipython,'already_called'):
         return
     start_ipython.already_called = True
 
     # Ok,  first time we're called, go ahead
     from IPython.core import ipapp, iplib
     
     def xsys(cmd):
         """Execute a command and print its output.
 
         This is just a convenience function to replace the IPython system call
         with one that is more doctest-friendly.
         """
         cmd = _ip.var_expand(cmd,depth=1)
         sys.stdout.write(commands.getoutput(cmd))
         sys.stdout.flush()
 
     # Store certain global objects that IPython modifies
     _displayhook = sys.displayhook
     _excepthook = sys.excepthook
     _main = sys.modules.get('__main__')
 
+    # Create custom argv and namespaces for our IPython to be test-friendly
     argv = tools.default_argv()
+    user_ns, global_ns = iplib.make_user_namespaces(ipnsdict(), {})
     
-    # Start IPython instance.  We customize it to start with minimal frills.
-    user_ns,global_ns = iplib.make_user_namespaces(ipnsdict(),{})
+    # Create and initialize our test-friendly IPython instance.
     ip = ipapp.IPythonApp(argv, user_ns=user_ns, user_global_ns=global_ns)
     ip.initialize()
+
+    # A few more tweaks needed for playing nicely with doctests...
+    
+    # These traps are normally only active for interactive use, set them
+    # permanently since we'll be mocking interactive sessions.
     ip.shell.builtin_trap.set()
 
     # Set error printing to stdout so nose can doctest exceptions
     ip.shell.InteractiveTB.out_stream = 'stdout'
     
+    # Modify the IPython system call with one that uses getoutput, so that we
+    # can capture subcommands and print them to Python's stdout, otherwise the
+    # doctest machinery would miss them.
+    ip.shell.system = xsys
+
+    # IPython is ready, now clean up some global state...
+    
     # Deactivate the various python system hooks added by ipython for
     # interactive convenience so we don't confuse the doctest system
     sys.modules['__main__'] = _main
     sys.displayhook = _displayhook
     sys.excepthook = _excepthook
 
     # So that ipython magics and aliases can be doctested (they work by making
     # a call into a global _ip object).  Also make the top-level get_ipython
-    # now return this without calling here again
+    # now return this without recursively calling here again.
     _ip = ip.shell
     get_ipython = _ip.get_ipython
     __builtin__._ip = _ip
     __builtin__.get_ipython = get_ipython
 
-    # Modify the IPython system call with one that uses getoutput, so that we
-    # can capture subcommands and print them to Python's stdout, otherwise the
-    # doctest machinery would miss them.
-    ip.shell.system = xsys
-
     return _ip