Allow IPython to start when PYTHONOPTIMIZE=2

Closes gh-8971

IPython/utils/py3compat.py

@@ -1,332 +1,334 b''
 # coding: utf-8
 """Compatibility tricks for Python 3. Mainly to do with unicode."""
 import functools
 import os
 import sys
 import re
 import shutil
 import types
 
 from .encoding import DEFAULT_ENCODING
 
 def no_code(x, encoding=None):
     return x
 
 def decode(s, encoding=None):
     encoding = encoding or DEFAULT_ENCODING
     return s.decode(encoding, "replace")
 
 def encode(u, encoding=None):
     encoding = encoding or DEFAULT_ENCODING
     return u.encode(encoding, "replace")
 
 
 def cast_unicode(s, encoding=None):
     if isinstance(s, bytes):
         return decode(s, encoding)
     return s
 
 def cast_bytes(s, encoding=None):
     if not isinstance(s, bytes):
         return encode(s, encoding)
     return s
 
 def buffer_to_bytes(buf):
     """Cast a buffer object to bytes"""
     if not isinstance(buf, bytes):
         buf = bytes(buf)
     return buf
 
 def _modify_str_or_docstring(str_change_func):
     @functools.wraps(str_change_func)
     def wrapper(func_or_str):
         if isinstance(func_or_str, string_types):
             func = None
             doc = func_or_str
         else:
             func = func_or_str
             doc = func.__doc__
         
-        doc = str_change_func(doc)
+        # PYTHONOPTIMIZE=2 strips docstrings, so they can disappear unexpectedly
+        if doc is not None:
+            doc = str_change_func(doc)
         
         if func:
             func.__doc__ = doc
             return func
         return doc
     return wrapper
 
 def safe_unicode(e):
     """unicode(e) with various fallbacks. Used for exceptions, which may not be
     safe to call unicode() on.
     """
     try:
         return unicode_type(e)
     except UnicodeError:
         pass
 
     try:
         return str_to_unicode(str(e))
     except UnicodeError:
         pass
 
     try:
         return str_to_unicode(repr(e))
     except UnicodeError:
         pass
 
     return u'Unrecoverably corrupt evalue'
 
 # shutil.which from Python 3.4
 def _shutil_which(cmd, mode=os.F_OK | os.X_OK, path=None):
     """Given a command, mode, and a PATH string, return the path which
     conforms to the given mode on the PATH, or None if there is no such
     file.
 
     `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result
     of os.environ.get("PATH"), or can be overridden with a custom search
     path.
     
     This is a backport of shutil.which from Python 3.4
     """
     # Check that a given file can be accessed with the correct mode.
     # Additionally check that `file` is not a directory, as on Windows
     # directories pass the os.access check.
     def _access_check(fn, mode):
         return (os.path.exists(fn) and os.access(fn, mode)
                 and not os.path.isdir(fn))
 
     # If we're given a path with a directory part, look it up directly rather
     # than referring to PATH directories. This includes checking relative to the
     # current directory, e.g. ./script
     if os.path.dirname(cmd):
         if _access_check(cmd, mode):
             return cmd
         return None
 
     if path is None:
         path = os.environ.get("PATH", os.defpath)
     if not path:
         return None
     path = path.split(os.pathsep)
 
     if sys.platform == "win32":
         # The current directory takes precedence on Windows.
         if not os.curdir in path:
             path.insert(0, os.curdir)
 
         # PATHEXT is necessary to check on Windows.
         pathext = os.environ.get("PATHEXT", "").split(os.pathsep)
         # See if the given file matches any of the expected path extensions.
         # This will allow us to short circuit when given "python.exe".
         # If it does match, only test that one, otherwise we have to try
         # others.
         if any(cmd.lower().endswith(ext.lower()) for ext in pathext):
             files = [cmd]
         else:
             files = [cmd + ext for ext in pathext]
     else:
         # On other platforms you don't have things like PATHEXT to tell you
         # what file suffixes are executable, so just pass on cmd as-is.
         files = [cmd]
 
     seen = set()
     for dir in path:
         normdir = os.path.normcase(dir)
         if not normdir in seen:
             seen.add(normdir)
             for thefile in files:
                 name = os.path.join(dir, thefile)
                 if _access_check(name, mode):
                     return name
     return None
 
 if sys.version_info[0] >= 3:
     PY3 = True
     
     # keep reference to builtin_mod because the kernel overrides that value
     # to forward requests to a frontend.
     def input(prompt=''):
         return builtin_mod.input(prompt)
     
     builtin_mod_name = "builtins"
     import builtins as builtin_mod
     
     str_to_unicode = no_code
     unicode_to_str = no_code
     str_to_bytes = encode
     bytes_to_str = decode
     cast_bytes_py2 = no_code
     cast_unicode_py2 = no_code
     buffer_to_bytes_py2 = no_code
     
     string_types = (str,)
     unicode_type = str
     
     which = shutil.which
     
     def isidentifier(s, dotted=False):
         if dotted:
             return all(isidentifier(a) for a in s.split("."))
         return s.isidentifier()
 
     xrange = range
     def iteritems(d): return iter(d.items())
     def itervalues(d): return iter(d.values())
     getcwd = os.getcwd
     
     MethodType = types.MethodType
 
     def execfile(fname, glob, loc=None, compiler=None):
         loc = loc if (loc is not None) else glob
         with open(fname, 'rb') as f:
             compiler = compiler or compile
             exec(compiler(f.read(), fname, 'exec'), glob, loc)
     
     # Refactor print statements in doctests.
     _print_statement_re = re.compile(r"\bprint (?P<expr>.*)$", re.MULTILINE)
     def _print_statement_sub(match):
         expr = match.groups('expr')
         return "print(%s)" % expr
     
     @_modify_str_or_docstring
     def doctest_refactor_print(doc):
         """Refactor 'print x' statements in a doctest to print(x) style. 2to3
         unfortunately doesn't pick up on our doctests.
         
         Can accept a string or a function, so it can be used as a decorator."""
         return _print_statement_re.sub(_print_statement_sub, doc)
     
     # Abstract u'abc' syntax:
     @_modify_str_or_docstring
     def u_format(s):
         """"{u}'abc'" --> "'abc'" (Python 3)
         
         Accepts a string or a function, so it can be used as a decorator."""
         return s.format(u='')
     
     def get_closure(f):
         """Get a function's closure attribute"""
         return f.__closure__
 
 else:
     PY3 = False
     
     # keep reference to builtin_mod because the kernel overrides that value
     # to forward requests to a frontend.
     def input(prompt=''):
         return builtin_mod.raw_input(prompt)
     
     builtin_mod_name = "__builtin__"
     import __builtin__ as builtin_mod
     
     str_to_unicode = decode
     unicode_to_str = encode
     str_to_bytes = no_code
     bytes_to_str = no_code
     cast_bytes_py2 = cast_bytes
     cast_unicode_py2 = cast_unicode
     buffer_to_bytes_py2 = buffer_to_bytes
     
     string_types = (str, unicode)
     unicode_type = unicode
     
     import re
     _name_re = re.compile(r"[a-zA-Z_][a-zA-Z0-9_]*$")
     def isidentifier(s, dotted=False):
         if dotted:
             return all(isidentifier(a) for a in s.split("."))
         return bool(_name_re.match(s))
     
     xrange = xrange
     def iteritems(d): return d.iteritems()
     def itervalues(d): return d.itervalues()
     getcwd = os.getcwdu
 
     def MethodType(func, instance):
         return types.MethodType(func, instance, type(instance))
     
     def doctest_refactor_print(func_or_str):
         return func_or_str
 
     def get_closure(f):
         """Get a function's closure attribute"""
         return f.func_closure
     
     which = _shutil_which
 
     # Abstract u'abc' syntax:
     @_modify_str_or_docstring
     def u_format(s):
         """"{u}'abc'" --> "u'abc'" (Python 2)
         
         Accepts a string or a function, so it can be used as a decorator."""
         return s.format(u='u')
 
     if sys.platform == 'win32':
         def execfile(fname, glob=None, loc=None, compiler=None):
             loc = loc if (loc is not None) else glob
             scripttext = builtin_mod.open(fname).read()+ '\n'
             # compile converts unicode filename to str assuming
             # ascii. Let's do the conversion before calling compile
             if isinstance(fname, unicode):
                 filename = unicode_to_str(fname)
             else:
                 filename = fname
             compiler = compiler or compile
             exec(compiler(scripttext, filename, 'exec'), glob, loc)
 
     else:
         def execfile(fname, glob=None, loc=None, compiler=None):
             if isinstance(fname, unicode):
                 filename = fname.encode(sys.getfilesystemencoding())
             else:
                 filename = fname
             where = [ns for ns in [glob, loc] if ns is not None]
             if compiler is None:
                 builtin_mod.execfile(filename, *where)
             else:
                 scripttext = builtin_mod.open(fname).read().rstrip() + '\n'
                 exec(compiler(scripttext, filename, 'exec'), glob, loc)
 
 
 PY2 = not PY3
 
 
 def annotate(**kwargs):
     """Python 3 compatible function annotation for Python 2."""
     if not kwargs:
         raise ValueError('annotations must be provided as keyword arguments')
     def dec(f):
         if hasattr(f, '__annotations__'):
             for k, v in kwargs.items():
                 f.__annotations__[k] = v
         else:
             f.__annotations__ = kwargs
         return f
     return dec
 
 
 # Parts below taken from six:
 # Copyright (c) 2010-2013 Benjamin Peterson
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
 # in the Software without restriction, including without limitation the rights
 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 # copies of the Software, and to permit persons to whom the Software is
 # furnished to do so, subject to the following conditions:
 #
 # The above copyright notice and this permission notice shall be included in all
 # copies or substantial portions of the Software.
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
 def with_metaclass(meta, *bases):
     """Create a base class with a metaclass."""
     return meta("_NewBase", bases, {})