Fix deepreload on Python 3.

Closes gh-1622

IPython/lib/deepreload.py

@@ -1,320 +1,338 b''
 # -*- coding: utf-8 -*-
 """
 A module to change reload() so that it acts recursively.
 To enable it type::
 
     import __builtin__, deepreload
     __builtin__.reload = deepreload.reload
 
 You can then disable it with::
 
     __builtin__.reload = deepreload.original_reload
 
 Alternatively, you can add a dreload builtin alongside normal reload with::
 
     __builtin__.dreload = deepreload.reload
 
 This code is almost entirely based on knee.py, which is a Python
 re-implementation of hierarchical module import.
 """
 #*****************************************************************************
 #       Copyright (C) 2001 Nathaniel Gray <[e-mail]>
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #*****************************************************************************
 
 import __builtin__
+from contextlib import contextmanager
 import imp
 import sys
 
 from types import ModuleType
 from warnings import warn
 
+original_import = __builtin__.__import__
+
+@contextmanager
+def replace_import_hook(new_import):
+    saved_import = __builtin__.__import__
+    __builtin__.__import__ = new_import
+    try:
+        yield
+    finally:
+        __builtin__.__import__ = saved_import
+
 def get_parent(globals, level):
     """
     parent, name = get_parent(globals, level)
 
     Return the package that an import is being performed in.  If globals comes
     from the module foo.bar.bat (not itself a package), this returns the
     sys.modules entry for foo.bar.  If globals is from a package's __init__.py,
     the package's entry in sys.modules is returned.
 
     If globals doesn't come from a package or a module in a package, or a
     corresponding entry is not found in sys.modules, None is returned.
     """
     orig_level = level
 
     if not level or not isinstance(globals, dict):
         return None, ''
 
     pkgname = globals.get('__package__', None)
 
     if pkgname is not None:
         # __package__ is set, so use it
         if not hasattr(pkgname, 'rindex'):
             raise ValueError('__package__ set to non-string')
         if len(pkgname) == 0:
             if level > 0:
                 raise ValueError('Attempted relative import in non-package')
             return None, ''
         name = pkgname
     else:
         # __package__ not set, so figure it out and set it
         if '__name__' not in globals:
             return None, ''
         modname = globals['__name__']
 
         if '__path__' in globals:
             # __path__ is set, so modname is already the package name
             globals['__package__'] = name = modname
         else:
             # Normal module, so work out the package name if any
             lastdot = modname.rfind('.')
             if lastdot < 0 and level > 0:
                 raise ValueError("Attempted relative import in non-package")
             if lastdot < 0:
                 globals['__package__'] = None
                 return None, ''
             globals['__package__'] = name = modname[:lastdot]
 
     dot = len(name)
     for x in xrange(level, 1, -1):
         try:
             dot = name.rindex('.', 0, dot)
         except ValueError:
             raise ValueError("attempted relative import beyond top-level "
                              "package")
     name = name[:dot]
 
     try:
         parent = sys.modules[name]
     except:
         if orig_level < 1:
             warn("Parent module '%.200s' not found while handling absolute "
                  "import" % name)
             parent = None
         else:
             raise SystemError("Parent module '%.200s' not loaded, cannot "
                               "perform relative import" % name)
 
     # We expect, but can't guarantee, if parent != None, that:
     # - parent.__name__ == name
     # - parent.__dict__ is globals
     # If this is violated...  Who cares?
     return parent, name
 
 def load_next(mod, altmod, name, buf):
     """
     mod, name, buf = load_next(mod, altmod, name, buf)
 
     altmod is either None or same as mod
     """
 
     if len(name) == 0:
         # completely empty module name should only happen in
         # 'from . import' (or '__import__("")')
         return mod, None, buf
 
     dot = name.find('.')
     if dot == 0:
         raise ValueError('Empty module name')
 
     if dot < 0:
         subname = name
         next = None
     else:
         subname = name[:dot]
         next = name[dot+1:]
 
     if buf != '':
         buf += '.'
     buf += subname
 
     result = import_submodule(mod, subname, buf)
     if result is None and mod != altmod:
         result = import_submodule(altmod, subname, subname)
         if result is not None:
             buf = subname
 
     if result is None:
         raise ImportError("No module named %.200s" % name)
 
     return result, next, buf
 
 # Need to keep track of what we've already reloaded to prevent cyclic evil
 found_now = {}
 
 def import_submodule(mod, subname, fullname):
     """m = import_submodule(mod, subname, fullname)"""
     # Require:
     # if mod == None: subname == fullname
     # else: mod.__name__ + "." + subname == fullname
 
     global found_now
     if fullname in found_now and fullname in sys.modules:
         m = sys.modules[fullname]
     else:
         print 'Reloading', fullname
         found_now[fullname] = 1
         oldm = sys.modules.get(fullname, None)
 
         if mod is None:
             path = None
         elif hasattr(mod, '__path__'):
             path = mod.__path__
         else:
             return None
 
         try:
-            fp, filename, stuff  = imp.find_module(subname, path)
+            # This appears to be necessary on Python 3, because imp.find_module()
+            # tries to import standard libraries (like io) itself, and we don't
+            # want them to be processed by our deep_import_hook.
+            with replace_import_hook(original_import):
+                fp, filename, stuff = imp.find_module(subname, path)
         except ImportError:
             return None
 
         try:
             m = imp.load_module(fullname, fp, filename, stuff)
         except:
             # load_module probably removed name from modules because of
             # the error.  Put back the original module object.
             if oldm:
                 sys.modules[fullname] = oldm
             raise
         finally:
             if fp: fp.close()
 
         add_submodule(mod, m, fullname, subname)
 
     return m
 
 def add_submodule(mod, submod, fullname, subname):
     """mod.{subname} = submod"""
     if mod is None:
         return #Nothing to do here.
 
     if submod is None:
         submod = sys.modules[fullname]
 
     setattr(mod, subname, submod)
 
     return
 
 def ensure_fromlist(mod, fromlist, buf, recursive):
     """Handle 'from module import a, b, c' imports."""
     if not hasattr(mod, '__path__'):
         return
     for item in fromlist:
         if not hasattr(item, 'rindex'):
             raise TypeError("Item in ``from list'' not a string")
         if item == '*':
             if recursive:
                 continue # avoid endless recursion
             try:
                 all = mod.__all__
             except AttributeError:
                 pass
             else:
                 ret = ensure_fromlist(mod, all, buf, 1)
                 if not ret:
                     return 0
         elif not hasattr(mod, item):
             import_submodule(mod, item, buf + '.' + item)
 
 def deep_import_hook(name, globals=None, locals=None, fromlist=None, level=-1):
     """Replacement for __import__()"""
     parent, buf = get_parent(globals, level)
 
     head, name, buf = load_next(parent, None if level < 0 else parent, name, buf)
 
     tail = head
     while name:
         tail, name, buf = load_next(tail, tail, name, buf)
 
     # If tail is None, both get_parent and load_next found
     # an empty module name: someone called __import__("") or
     # doctored faulty bytecode
     if tail is None:
         raise ValueError('Empty module name')
 
     if not fromlist:
         return head
 
     ensure_fromlist(tail, fromlist, buf, 0)
     return tail
 
 modules_reloading = {}
 
 def deep_reload_hook(m):
     """Replacement for reload()."""
     if not isinstance(m, ModuleType):
         raise TypeError("reload() argument must be module")
 
     name = m.__name__
 
     if name not in sys.modules:
         raise ImportError("reload(): module %.200s not in sys.modules" % name)
 
     global modules_reloading
     try:
         return modules_reloading[name]
     except:
         modules_reloading[name] = m
 
     dot = name.rfind('.')
     if dot < 0:
         subname = name
         path = None
     else:
         try:
             parent = sys.modules[name[:dot]]
         except KeyError:
             modules_reloading.clear()
             raise ImportError("reload(): parent %.200s not in sys.modules" % name[:dot])
         subname = name[dot+1:]
         path = getattr(parent, "__path__", None)
 
     try:
-        fp, filename, stuff  = imp.find_module(subname, path)
+        # This appears to be necessary on Python 3, because imp.find_module()
+        # tries to import standard libraries (like io) itself, and we don't
+        # want them to be processed by our deep_import_hook.
+        with replace_import_hook(original_import):
+            fp, filename, stuff  = imp.find_module(subname, path)
     finally:
         modules_reloading.clear()
 
     try:
         newm = imp.load_module(name, fp, filename, stuff)
     except:
          # load_module probably removed name from modules because of
          # the error.  Put back the original module object.
         sys.modules[name] = m
         raise
     finally:
         if fp: fp.close()
 
     modules_reloading.clear()
     return newm
 
 # Save the original hooks
 try:
     original_reload = __builtin__.reload
 except AttributeError:
     original_reload = imp.reload    # Python 3
 
 # Replacement for reload()
 def reload(module, exclude=['sys', 'os.path', '__builtin__', '__main__']):
     """Recursively reload all modules used in the given module.  Optionally
     takes a list of modules to exclude from reloading.  The default exclude
     list contains sys, __main__, and __builtin__, to prevent, e.g., resetting
     display, exception, and io hooks.
     """
     global found_now
     for i in exclude:
         found_now[i] = 1
-    original_import = __builtin__.__import__
-    __builtin__.__import__ = deep_import_hook
     try:
-        ret = deep_reload_hook(module)
+        with replace_import_hook(deep_import_hook):
+            ret = deep_reload_hook(module)
     finally:
-        __builtin__.__import__ = original_import
         found_now = {}
     return ret
 
 # Uncomment the following to automatically activate deep reloading whenever
 # this module is imported
 #__builtin__.reload = reload