Port `deepreload` to `importlib`

`imp` is deprecated since Python 3.3 and scheduled for removal in Python 3.12

The code is severely undertested, I added several, and also fixed a bug that `modules_reloading` was not cleaned-up on an import failure.

IPython/lib/deepreload.py

@@ -1,341 +1,299 b''
 # -*- coding: utf-8 -*-
 """
 Provides a reload() function that acts recursively.
 
 Python's normal :func:`python:reload` function only reloads the module that it's
 passed. The :func:`reload` function in this module also reloads everything
 imported from that module, which is useful when you're changing files deep
 inside a package.
 
 To use this as your default reload function, type this::
 
     import builtins
     from IPython.lib import deepreload
     builtins.reload = deepreload.reload
 
 A reference to the original :func:`python:reload` is stored in this module as
 :data:`original_reload`, so you can restore it later.
 
 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 builtins as builtin_mod
 from contextlib import contextmanager
-import imp
+import importlib
 import sys
 
 from types import ModuleType
 from warnings import warn
 import types
 
 original_import = builtin_mod.__import__
 
 @contextmanager
 def replace_import_hook(new_import):
     saved_import = builtin_mod.__import__
     builtin_mod.__import__ = new_import
     try:
         yield
     finally:
         builtin_mod.__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 < level:
                 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 range(level, 1, -1):
         try:
             dot = name.rindex('.', 0, dot)
         except ValueError as e:
             raise ValueError("attempted relative import beyond top-level "
                              "package") from e
     name = name[:dot]
 
     try:
         parent = sys.modules[name]
     except BaseException as e:
         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) from e
 
     # 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:
-            # 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)
+            if oldm is not None:
+                m = importlib.reload(oldm)
+            else:
+                m = importlib.import_module(subname, mod)
         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()."""
     # Hardcode this one  as it would raise a NotImplementedError from the
     # bowels of Python and screw up the import machinery after.
     # unlike other imports the `exclude` list already in place is not enough.
 
     if m is types:
         return m
     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 as e:
-            modules_reloading.clear()
-            raise ImportError("reload(): parent %.200s not in sys.modules" % name[:dot]) from e
-        subname = name[dot+1:]
-        path = getattr(parent, "__path__", None)
-
-    try:
-        # 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)
+        newm = importlib.reload(m)
     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()
+        modules_reloading.clear()
     return newm
 
 # Save the original hooks
-original_reload = imp.reload
+original_reload = importlib.reload
 
 # Replacement for reload()
 def reload(module, exclude=('sys', 'os.path', 'builtins', '__main__',
                             'numpy', 'numpy._globals')):
     """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
     try:
         with replace_import_hook(deep_import_hook):
             return deep_reload_hook(module)
     finally:
         found_now = {}

IPython/lib/tests/test_deepreload.py

@@ -1,34 +1,56 b''
 # -*- coding: utf-8 -*-
 """Test suite for the deepreload module."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
+import pytest
+import types
+
 from pathlib import Path
 
 from IPython.utils.syspathcontext import prepended_to_syspath
 from IPython.utils.tempdir import TemporaryDirectory
-from IPython.lib.deepreload import reload as dreload
+from IPython.lib.deepreload import reload as dreload, modules_reloading
 
 
 def test_deepreload():
     "Test that dreload does deep reloads and skips excluded modules."
     with TemporaryDirectory() as tmpdir:
         with prepended_to_syspath(tmpdir):
             tmpdirpath = Path(tmpdir)
             with open(tmpdirpath / "A.py", "w") as f:
-                f.write("class Object(object):\n    pass\n")
+                f.write("class Object:\n    pass\nok = True\n")
             with open(tmpdirpath / "B.py", "w") as f:
-                f.write("import A\n")
+                f.write("import A\nassert A.ok, 'we are fine'\n")
             import A
             import B
 
             # Test that A is not reloaded.
             obj = A.Object()
             dreload(B, exclude=["A"])
             assert isinstance(obj, A.Object) is True
 
+            # Test that an import failure will not blow-up us.
+            A.ok = False
+            with pytest.raises(AssertionError, match="we are fine"):
+                dreload(B, exclude=["A"])
+            assert len(modules_reloading) == 0
+            assert not A.ok
+
             # Test that A is reloaded.
             obj = A.Object()
+            A.ok = False
             dreload(B)
+            assert A.ok
             assert isinstance(obj, A.Object) is False
+
+
+def test_not_module():
+    pytest.raises(TypeError, dreload, "modulename")
+
+
+def test_not_in_sys_modules():
+    fake_module = types.ModuleType("fake_module")
+    with pytest.raises(ImportError, match="not in sys.modules"):
+        dreload(fake_module)