add CWD to sys.path *after* stdlib

this deviates from Python's own interactive behavior,
but seems to avoid problems where folks create stdlib-names like `email.py`.

They can still collide with packages,
but that seems less common than generic names like `email` and `code`

IPython/core/shellapp.py

@@ -1,408 +1,425 b''
 # encoding: utf-8
 """
 A mixin for :class:`~IPython.core.application.Application` classes that
 launch InteractiveShell instances, load extensions, etc.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import glob
 from itertools import chain
 import os
 import sys
 
 from traitlets.config.application import boolean_flag
 from traitlets.config.configurable import Configurable
 from traitlets.config.loader import Config
 from IPython.core.application import SYSTEM_CONFIG_DIRS, ENV_CONFIG_DIRS
 from IPython.core import pylabtools
 from IPython.utils.contexts import preserve_keys
 from IPython.utils.path import filefind
 from traitlets import (
     Unicode, Instance, List, Bool, CaselessStrEnum, observe,
 )
 from IPython.terminal import pt_inputhooks
 
 #-----------------------------------------------------------------------------
 # Aliases and Flags
 #-----------------------------------------------------------------------------
 
 gui_keys = tuple(sorted(pt_inputhooks.backends) + sorted(pt_inputhooks.aliases))
 
 backend_keys = sorted(pylabtools.backends.keys())
 backend_keys.insert(0, 'auto')
 
 shell_flags = {}
 
 addflag = lambda *args: shell_flags.update(boolean_flag(*args))
 addflag('autoindent', 'InteractiveShell.autoindent',
         'Turn on autoindenting.', 'Turn off autoindenting.'
 )
 addflag('automagic', 'InteractiveShell.automagic',
         """Turn on the auto calling of magic commands. Type %%magic at the
         IPython  prompt  for  more information.""",
         'Turn off the auto calling of magic commands.'
 )
 addflag('pdb', 'InteractiveShell.pdb',
     "Enable auto calling the pdb debugger after every exception.",
     "Disable auto calling the pdb debugger after every exception."
 )
 addflag('pprint', 'PlainTextFormatter.pprint',
     "Enable auto pretty printing of results.",
     "Disable auto pretty printing of results."
 )
 addflag('color-info', 'InteractiveShell.color_info',
     """IPython can display information about objects via a set of functions,
     and optionally can use colors for this, syntax highlighting
     source code and various other elements. This is on by default, but can cause
     problems with some pagers. If you see such problems, you can disable the
     colours.""",
     "Disable using colors for info related things."
 )
 nosep_config = Config()
 nosep_config.InteractiveShell.separate_in = ''
 nosep_config.InteractiveShell.separate_out = ''
 nosep_config.InteractiveShell.separate_out2 = ''
 
 shell_flags['nosep']=(nosep_config, "Eliminate all spacing between prompts.")
 shell_flags['pylab'] = (
     {'InteractiveShellApp' : {'pylab' : 'auto'}},
     """Pre-load matplotlib and numpy for interactive use with
     the default matplotlib backend."""
 )
 shell_flags['matplotlib'] = (
     {'InteractiveShellApp' : {'matplotlib' : 'auto'}},
     """Configure matplotlib for interactive use with
     the default matplotlib backend."""
 )
 
 # it's possible we don't want short aliases for *all* of these:
 shell_aliases = dict(
     autocall='InteractiveShell.autocall',
     colors='InteractiveShell.colors',
     logfile='InteractiveShell.logfile',
     logappend='InteractiveShell.logappend',
     c='InteractiveShellApp.code_to_run',
     m='InteractiveShellApp.module_to_run',
     ext='InteractiveShellApp.extra_extension',
     gui='InteractiveShellApp.gui',
     pylab='InteractiveShellApp.pylab',
     matplotlib='InteractiveShellApp.matplotlib',
 )
 shell_aliases['cache-size'] = 'InteractiveShell.cache_size'
 
 #-----------------------------------------------------------------------------
 # Main classes and functions
 #-----------------------------------------------------------------------------
 
 class InteractiveShellApp(Configurable):
     """A Mixin for applications that start InteractiveShell instances.
 
     Provides configurables for loading extensions and executing files
     as part of configuring a Shell environment.
 
     The following methods should be called by the :meth:`initialize` method
     of the subclass:
 
       - :meth:`init_path`
       - :meth:`init_shell` (to be implemented by the subclass)
       - :meth:`init_gui_pylab`
       - :meth:`init_extensions`
       - :meth:`init_code`
     """
     extensions = List(Unicode(),
         help="A list of dotted module names of IPython extensions to load."
     ).tag(config=True)
     extra_extension = Unicode('',
         help="dotted module name of an IPython extension to load."
     ).tag(config=True)
 
     reraise_ipython_extension_failures = Bool(False,
         help="Reraise exceptions encountered loading IPython extensions?",
     ).tag(config=True)
 
     # Extensions that are always loaded (not configurable)
     default_extensions = List(Unicode(), [u'storemagic']).tag(config=False)
 
     hide_initial_ns = Bool(True,
         help="""Should variables loaded at startup (by startup files, exec_lines, etc.)
         be hidden from tools like %who?"""
     ).tag(config=True)
 
     exec_files = List(Unicode(),
         help="""List of files to run at IPython startup."""
     ).tag(config=True)
     exec_PYTHONSTARTUP = Bool(True,
         help="""Run the file referenced by the PYTHONSTARTUP environment
         variable at IPython startup."""
     ).tag(config=True)
     file_to_run = Unicode('',
         help="""A file to be run""").tag(config=True)
 
     exec_lines = List(Unicode(),
         help="""lines of code to run at IPython startup."""
     ).tag(config=True)
     code_to_run = Unicode('',
         help="Execute the given command string."
     ).tag(config=True)
     module_to_run = Unicode('',
         help="Run the module as a script."
     ).tag(config=True)
     gui = CaselessStrEnum(gui_keys, allow_none=True,
         help="Enable GUI event loop integration with any of {0}.".format(gui_keys)
     ).tag(config=True)
     matplotlib = CaselessStrEnum(backend_keys, allow_none=True,
         help="""Configure matplotlib for interactive use with
         the default matplotlib backend."""
     ).tag(config=True)
     pylab = CaselessStrEnum(backend_keys, allow_none=True,
         help="""Pre-load matplotlib and numpy for interactive use,
         selecting a particular matplotlib backend and loop integration.
         """
     ).tag(config=True)
     pylab_import_all = Bool(True,
         help="""If true, IPython will populate the user namespace with numpy, pylab, etc.
         and an ``import *`` is done from numpy and pylab, when using pylab mode.
 
         When False, pylab mode should not import any names into the user namespace.
         """
     ).tag(config=True)
     shell = Instance('IPython.core.interactiveshell.InteractiveShellABC',
                      allow_none=True)
     # whether interact-loop should start
     interact = Bool(True)
 
     user_ns = Instance(dict, args=None, allow_none=True)
     @observe('user_ns')
     def _user_ns_changed(self, change):
         if self.shell is not None:
             self.shell.user_ns = change['new']
             self.shell.init_user_ns()
 
     def init_path(self):
-        """Add current working directory, '', to sys.path"""
-        if sys.path[0] != '':
-            sys.path.insert(0, '')
+        """Add current working directory, '', to sys.path
+
+        Unlike Python's default, we insert before the first `site-packages`
+        or `dist-packages` directory,
+        so that it is after the standard library.
+
+        .. versionchanged:: 7.2
+            Try to insert after the standard library, instead of first.
+        """
+        if '' in sys.path:
+            return
+        for idx, path in enumerate(sys.path):
+            parent, last_part = os.path.split(path)
+            if last_part in {'site-packages', 'dist-packages'}:
+                break
+        else:
+            # no site-packages or dist-packages found (?!)
+            # back to original behavior of inserting at the front
+            idx = 0
+        sys.path.insert(idx, '')
 
     def init_shell(self):
         raise NotImplementedError("Override in subclasses")
 
     def init_gui_pylab(self):
         """Enable GUI event loop integration, taking pylab into account."""
         enable = False
         shell = self.shell
         if self.pylab:
             enable = lambda key: shell.enable_pylab(key, import_all=self.pylab_import_all)
             key = self.pylab
         elif self.matplotlib:
             enable = shell.enable_matplotlib
             key = self.matplotlib
         elif self.gui:
             enable = shell.enable_gui
             key = self.gui
 
         if not enable:
             return
 
         try:
             r = enable(key)
         except ImportError:
             self.log.warning("Eventloop or matplotlib integration failed. Is matplotlib installed?")
             self.shell.showtraceback()
             return
         except Exception:
             self.log.warning("GUI event loop or pylab initialization failed")
             self.shell.showtraceback()
             return
 
         if isinstance(r, tuple):
             gui, backend = r[:2]
             self.log.info("Enabling GUI event loop integration, "
                       "eventloop=%s, matplotlib=%s", gui, backend)
             if key == "auto":
                 print("Using matplotlib backend: %s" % backend)
         else:
             gui = r
             self.log.info("Enabling GUI event loop integration, "
                       "eventloop=%s", gui)
 
     def init_extensions(self):
         """Load all IPython extensions in IPythonApp.extensions.
 
         This uses the :meth:`ExtensionManager.load_extensions` to load all
         the extensions listed in ``self.extensions``.
         """
         try:
             self.log.debug("Loading IPython extensions...")
             extensions = self.default_extensions + self.extensions
             if self.extra_extension:
                 extensions.append(self.extra_extension)
             for ext in extensions:
                 try:
                     self.log.info("Loading IPython extension: %s" % ext)
                     self.shell.extension_manager.load_extension(ext)
                 except:
                     if self.reraise_ipython_extension_failures:
                         raise
                     msg = ("Error in loading extension: {ext}\n"
                            "Check your config files in {location}".format(
                                ext=ext,
                                location=self.profile_dir.location
                            ))
                     self.log.warning(msg, exc_info=True)
         except:
             if self.reraise_ipython_extension_failures:
                 raise
             self.log.warning("Unknown error in loading extensions:", exc_info=True)
 
     def init_code(self):
         """run the pre-flight code, specified via exec_lines"""
         self._run_startup_files()
         self._run_exec_lines()
         self._run_exec_files()
 
         # Hide variables defined here from %who etc.
         if self.hide_initial_ns:
             self.shell.user_ns_hidden.update(self.shell.user_ns)
 
         # command-line execution (ipython -i script.py, ipython -m module)
         # should *not* be excluded from %whos
         self._run_cmd_line_code()
         self._run_module()
 
         # flush output, so itwon't be attached to the first cell
         sys.stdout.flush()
         sys.stderr.flush()
 
     def _run_exec_lines(self):
         """Run lines of code in IPythonApp.exec_lines in the user's namespace."""
         if not self.exec_lines:
             return
         try:
             self.log.debug("Running code from IPythonApp.exec_lines...")
             for line in self.exec_lines:
                 try:
                     self.log.info("Running code in user namespace: %s" %
                                   line)
                     self.shell.run_cell(line, store_history=False)
                 except:
                     self.log.warning("Error in executing line in user "
                                   "namespace: %s" % line)
                     self.shell.showtraceback()
         except:
             self.log.warning("Unknown error in handling IPythonApp.exec_lines:")
             self.shell.showtraceback()
 
     def _exec_file(self, fname, shell_futures=False):
         try:
             full_filename = filefind(fname, [u'.', self.ipython_dir])
         except IOError:
             self.log.warning("File not found: %r"%fname)
             return
         # Make sure that the running script gets a proper sys.argv as if it
         # were run from a system shell.
         save_argv = sys.argv
         sys.argv = [full_filename] + self.extra_args[1:]
         try:
             if os.path.isfile(full_filename):
                 self.log.info("Running file in user namespace: %s" %
                               full_filename)
                 # Ensure that __file__ is always defined to match Python
                 # behavior.
                 with preserve_keys(self.shell.user_ns, '__file__'):
                     self.shell.user_ns['__file__'] = fname
                     if full_filename.endswith('.ipy'):
                         self.shell.safe_execfile_ipy(full_filename,
                                                      shell_futures=shell_futures)
                     else:
                         # default to python, even without extension
                         self.shell.safe_execfile(full_filename,
                                                  self.shell.user_ns,
                                                  shell_futures=shell_futures,
                                                  raise_exceptions=True)
         finally:
             sys.argv = save_argv
 
     def _run_startup_files(self):
         """Run files from profile startup directory"""
         startup_dirs = [self.profile_dir.startup_dir] + [
             os.path.join(p, 'startup') for p in chain(ENV_CONFIG_DIRS, SYSTEM_CONFIG_DIRS)
         ]
         startup_files = []
 
         if self.exec_PYTHONSTARTUP and os.environ.get('PYTHONSTARTUP', False) and \
                 not (self.file_to_run or self.code_to_run or self.module_to_run):
             python_startup = os.environ['PYTHONSTARTUP']
             self.log.debug("Running PYTHONSTARTUP file %s...", python_startup)
             try:
                 self._exec_file(python_startup)
             except:
                 self.log.warning("Unknown error in handling PYTHONSTARTUP file %s:", python_startup)
                 self.shell.showtraceback()
         for startup_dir in startup_dirs[::-1]:
             startup_files += glob.glob(os.path.join(startup_dir, '*.py'))
             startup_files += glob.glob(os.path.join(startup_dir, '*.ipy'))
         if not startup_files:
             return
 
         self.log.debug("Running startup files from %s...", startup_dir)
         try:
             for fname in sorted(startup_files):
                 self._exec_file(fname)
         except:
             self.log.warning("Unknown error in handling startup files:")
             self.shell.showtraceback()
 
     def _run_exec_files(self):
         """Run files from IPythonApp.exec_files"""
         if not self.exec_files:
             return
 
         self.log.debug("Running files in IPythonApp.exec_files...")
         try:
             for fname in self.exec_files:
                 self._exec_file(fname)
         except:
             self.log.warning("Unknown error in handling IPythonApp.exec_files:")
             self.shell.showtraceback()
 
     def _run_cmd_line_code(self):
         """Run code or file specified at the command-line"""
         if self.code_to_run:
             line = self.code_to_run
             try:
                 self.log.info("Running code given at command line (c=): %s" %
                               line)
                 self.shell.run_cell(line, store_history=False)
             except:
                 self.log.warning("Error in executing line in user namespace: %s" %
                               line)
                 self.shell.showtraceback()
                 if not self.interact:
                     self.exit(1)
 
         # Like Python itself, ignore the second if the first of these is present
         elif self.file_to_run:
             fname = self.file_to_run
             if os.path.isdir(fname):
                 fname = os.path.join(fname, "__main__.py")
             try:
                 self._exec_file(fname, shell_futures=True)
             except:
                 self.shell.showtraceback(tb_offset=4)
                 if not self.interact:
                     self.exit(1)
 
     def _run_module(self):
         """Run module specified at the command-line."""
         if self.module_to_run:
             # Make sure that the module gets a proper sys.argv as if it were
             # run using `python -m`.
             save_argv = sys.argv
             sys.argv = [sys.executable] + self.extra_args
             try:
                 self.shell.safe_run_module(self.module_to_run,
                                            self.shell.user_ns)
             finally:
                 sys.argv = save_argv