Fixed #21674 -- Deprecated the import_by_path() function in favor of import_string().

Thanks Aymeric Augustin for the suggestion and review.

23 files changed, 89 insertions, 65 deletions

diff --git a/django/contrib/admin/tests.py b/django/contrib/admin/tests.py
index 40fd10089b..56b8b66023 100644
--- a/django/contrib/admin/tests.py
+++ b/django/contrib/admin/tests.py
@@ -2,7 +2,7 @@ import os
 from unittest import SkipTest
 
 from django.contrib.staticfiles.testing import StaticLiveServerCase
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils.translation import ugettext as _
 
 
@@ -22,7 +22,7 @@ class AdminSeleniumWebDriverTestCase(StaticLiveServerCase):
         if not os.environ.get('DJANGO_SELENIUM_TESTS', False):
             raise SkipTest('Selenium tests not requested')
         try:
-            cls.selenium = import_by_path(cls.webdriver_class)()
+            cls.selenium = import_string(cls.webdriver_class)()
         except Exception as e:
             raise SkipTest('Selenium webdriver "%s" not installed or not '
                            'operational: %s' % (cls.webdriver_class, str(e)))
diff --git a/django/contrib/auth/__init__.py b/django/contrib/auth/__init__.py
index 9fd46814b2..ed01da94cf 100644
--- a/django/contrib/auth/__init__.py
+++ b/django/contrib/auth/__init__.py
@@ -4,7 +4,7 @@ import re
 from django.apps import apps as django_apps
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured, PermissionDenied
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.middleware.csrf import rotate_token
 
 from .signals import user_logged_in, user_logged_out, user_login_failed
@@ -15,7 +15,7 @@ REDIRECT_FIELD_NAME = 'next'
 
 
 def load_backend(path):
-    return import_by_path(path)()
+    return import_string(path)()
 
 
 def get_backends():
diff --git a/django/contrib/auth/hashers.py b/django/contrib/auth/hashers.py
index 713240b502..992e19e2a4 100644
--- a/django/contrib/auth/hashers.py
+++ b/django/contrib/auth/hashers.py
@@ -13,7 +13,7 @@ from django.utils.encoding import force_bytes, force_str, force_text
 from django.core.exceptions import ImproperlyConfigured
 from django.utils.crypto import (
     pbkdf2, constant_time_compare, get_random_string)
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils.translation import ugettext_noop as _
 
 
@@ -92,7 +92,7 @@ def load_hashers(password_hashers=None):
     if not password_hashers:
         password_hashers = settings.PASSWORD_HASHERS
     for backend in password_hashers:
-        hasher = import_by_path(backend)()
+        hasher = import_string(backend)()
         if not getattr(hasher, 'algorithm'):
             raise ImproperlyConfigured("hasher doesn't specify an "
                                        "algorithm name: %s" % backend)
diff --git a/django/contrib/auth/middleware.py b/django/contrib/auth/middleware.py
index a107055e34..3ee742446d 100644
--- a/django/contrib/auth/middleware.py
+++ b/django/contrib/auth/middleware.py
@@ -58,7 +58,7 @@ class RemoteUserMiddleware(object):
                         auth.BACKEND_SESSION_KEY, ''))
                     if isinstance(stored_backend, RemoteUserBackend):
                         auth.logout(request)
-                except ImproperlyConfigured:
+                except ImportError:
                     # backend failed to load
                     auth.logout(request)
             return
diff --git a/django/contrib/formtools/wizard/storage/__init__.py b/django/contrib/formtools/wizard/storage/__init__.py
index 4dbc15a298..71a21f89a3 100644
--- a/django/contrib/formtools/wizard/storage/__init__.py
+++ b/django/contrib/formtools/wizard/storage/__init__.py
@@ -1,5 +1,4 @@
-from django.core.exceptions import ImproperlyConfigured
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 from django.contrib.formtools.wizard.storage.base import BaseStorage
 from django.contrib.formtools.wizard.storage.exceptions import (
@@ -12,7 +11,7 @@ __all__ = [
 
 def get_storage(path, *args, **kwargs):
     try:
-        storage_class = import_by_path(path)
-    except ImproperlyConfigured as e:
+        storage_class = import_string(path)
+    except ImportError as e:
         raise MissingStorage('Error loading storage: %s' % e)
     return storage_class(*args, **kwargs)
diff --git a/django/contrib/messages/storage/__init__.py b/django/contrib/messages/storage/__init__.py
index 591ae14d7c..373dbbaada 100644
--- a/django/contrib/messages/storage/__init__.py
+++ b/django/contrib/messages/storage/__init__.py
@@ -1,12 +1,12 @@
 from django.conf import settings
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 
 def default_storage(request):
     """
     Callable with the same interface as the storage classes.
 
-    This isn't just default_storage = import_by_path(settings.MESSAGE_STORAGE)
+    This isn't just default_storage = import_string(settings.MESSAGE_STORAGE)
     to avoid accessing the settings at the module level.
     """
-    return import_by_path(settings.MESSAGE_STORAGE)(request)
+    return import_string(settings.MESSAGE_STORAGE)(request)
diff --git a/django/contrib/sessions/backends/base.py b/django/contrib/sessions/backends/base.py
index 2a497fe9a1..a77a25bb31 100644
--- a/django/contrib/sessions/backends/base.py
+++ b/django/contrib/sessions/backends/base.py
@@ -12,7 +12,7 @@ from django.utils.crypto import get_random_string
 from django.utils.crypto import salted_hmac
 from django.utils import timezone
 from django.utils.encoding import force_bytes, force_text
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 from django.contrib.sessions.exceptions import SuspiciousSession
 
@@ -40,7 +40,7 @@ class SessionBase(object):
         self._session_key = session_key
         self.accessed = False
         self.modified = False
-        self.serializer = import_by_path(settings.SESSION_SERIALIZER)
+        self.serializer = import_string(settings.SESSION_SERIALIZER)
 
     def __contains__(self, key):
         return key in self._session
diff --git a/django/contrib/staticfiles/finders.py b/django/contrib/staticfiles/finders.py
index 30767405d3..86b620696f 100644
--- a/django/contrib/staticfiles/finders.py
+++ b/django/contrib/staticfiles/finders.py
@@ -6,7 +6,7 @@ from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.core.files.storage import default_storage, Storage, FileSystemStorage
 from django.utils.functional import empty, LazyObject
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils._os import safe_join
 from django.utils import six, lru_cache
 
@@ -257,7 +257,7 @@ def get_finder(import_path):
     Imports the staticfiles finder class described by import_path, where
     import_path is the full Python path to the class.
     """
-    Finder = import_by_path(import_path)
+    Finder = import_string(import_path)
     if not issubclass(Finder, BaseFinder):
         raise ImproperlyConfigured('Finder "%s" is not a subclass of "%s"' %
                                    (Finder, BaseFinder))
diff --git a/django/core/cache/__init__.py b/django/core/cache/__init__.py
index c362800dcc..603086a39c 100644
--- a/django/core/cache/__init__.py
+++ b/django/core/cache/__init__.py
@@ -20,7 +20,7 @@ from django.core import signals
 from django.core.cache.backends.base import (
     InvalidCacheBackendError, CacheKeyWarning, BaseCache)
 from django.core.exceptions import ImproperlyConfigured
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 
 __all__ = [
@@ -69,8 +69,8 @@ def _create_cache(backend, **kwargs):
         except KeyError:
             try:
                 # Trying to import the given backend, in case it's a dotted path
-                import_by_path(backend)
-            except ImproperlyConfigured as e:
+                import_string(backend)
+            except ImportError as e:
                 raise InvalidCacheBackendError("Could not find backend '%s': %s" % (
                     backend, e))
             location = kwargs.pop('LOCATION', '')
@@ -80,8 +80,8 @@ def _create_cache(backend, **kwargs):
             params.update(kwargs)
             backend = params.pop('BACKEND')
             location = params.pop('LOCATION', '')
-        backend_cls = import_by_path(backend)
-    except (AttributeError, ImportError, ImproperlyConfigured) as e:
+        backend_cls = import_string(backend)
+    except ImportError as e:
         raise InvalidCacheBackendError(
             "Could not find backend '%s': %s" % (backend, e))
     return backend_cls(location, params)
diff --git a/django/core/cache/backends/base.py b/django/core/cache/backends/base.py
index 2c3151369a..ae83865db8 100644
--- a/django/core/cache/backends/base.py
+++ b/django/core/cache/backends/base.py
@@ -5,7 +5,7 @@ import time
 import warnings
 
 from django.core.exceptions import ImproperlyConfigured, DjangoRuntimeWarning
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 
 class InvalidCacheBackendError(ImproperlyConfigured):
@@ -45,7 +45,7 @@ def get_key_func(key_func):
         if callable(key_func):
             return key_func
         else:
-            return import_by_path(key_func)
+            return import_string(key_func)
     return default_key_func
 
 
diff --git a/django/core/files/storage.py b/django/core/files/storage.py
index c8b4c7185d..ade1817dad 100644
--- a/django/core/files/storage.py
+++ b/django/core/files/storage.py
@@ -9,7 +9,7 @@ from django.core.files import locks, File
 from django.core.files.move import file_move_safe
 from django.utils.encoding import force_text, filepath_to_uri
 from django.utils.functional import LazyObject
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils.six.moves.urllib.parse import urljoin
 from django.utils.text import get_valid_filename
 from django.utils._os import safe_join, abspathu
@@ -301,7 +301,7 @@ class FileSystemStorage(Storage):
 
 
 def get_storage_class(import_path=None):
-    return import_by_path(import_path or settings.DEFAULT_FILE_STORAGE)
+    return import_string(import_path or settings.DEFAULT_FILE_STORAGE)
 
 
 class DefaultStorage(LazyObject):
diff --git a/django/core/files/uploadhandler.py b/django/core/files/uploadhandler.py
index 995e97a2f6..2fa1d7a934 100644
--- a/django/core/files/uploadhandler.py
+++ b/django/core/files/uploadhandler.py
@@ -9,7 +9,7 @@ from io import BytesIO
 from django.conf import settings
 from django.core.files.uploadedfile import TemporaryUploadedFile, InMemoryUploadedFile
 from django.utils.encoding import python_2_unicode_compatible
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 __all__ = [
     'UploadFileException', 'StopUpload', 'SkipFile', 'FileUploadHandler',
@@ -214,4 +214,4 @@ def load_handler(path, *args, **kwargs):
         <TemporaryFileUploadHandler object at 0x...>
 
     """
-    return import_by_path(path)(*args, **kwargs)
+    return import_string(path)(*args, **kwargs)
diff --git a/django/core/handlers/base.py b/django/core/handlers/base.py
index 587cbae2c3..3986257660 100644
--- a/django/core/handlers/base.py
+++ b/django/core/handlers/base.py
@@ -11,7 +11,7 @@ from django.core import signals
 from django.core.exceptions import MiddlewareNotUsed, PermissionDenied, SuspiciousOperation
 from django.db import connections, transaction
 from django.utils.encoding import force_text
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils import six
 from django.views import debug
 
@@ -43,7 +43,7 @@ class BaseHandler(object):
 
         request_middleware = []
         for middleware_path in settings.MIDDLEWARE_CLASSES:
-            mw_class = import_by_path(middleware_path)
+            mw_class = import_string(middleware_path)
             try:
                 mw_instance = mw_class()
             except MiddlewareNotUsed:
diff --git a/django/core/mail/__init__.py b/django/core/mail/__init__.py
index 5a01adc4ea..cef9d1b87b 100644
--- a/django/core/mail/__init__.py
+++ b/django/core/mail/__init__.py
@@ -4,7 +4,7 @@ Tools for sending email.
 from __future__ import unicode_literals
 
 from django.conf import settings
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 # Imported for backwards compatibility, and for the sake
 # of a cleaner namespace. These symbols used to be in
@@ -34,7 +34,7 @@ def get_connection(backend=None, fail_silently=False, **kwds):
     Both fail_silently and other keyword arguments are used in the
     constructor of the backend.
     """
-    klass = import_by_path(backend or settings.EMAIL_BACKEND)
+    klass = import_string(backend or settings.EMAIL_BACKEND)
     return klass(fail_silently=fail_silently, **kwds)
 
 
diff --git a/django/core/servers/basehttp.py b/django/core/servers/basehttp.py
index d34c246d51..090a694c3e 100644
--- a/django/core/servers/basehttp.py
+++ b/django/core/servers/basehttp.py
@@ -16,9 +16,11 @@ import traceback
 from wsgiref import simple_server
 from wsgiref.util import FileWrapper   # NOQA: for backwards compatibility
 
+from django.core.exceptions import ImproperlyConfigured
 from django.core.management.color import color_style
 from django.core.wsgi import get_wsgi_application
-from django.utils.module_loading import import_by_path
+from django.utils import six
+from django.utils.module_loading import import_string
 from django.utils.six.moves import socketserver
 
 __all__ = ('WSGIServer', 'WSGIRequestHandler', 'MAX_SOCKET_CHUNK_SIZE')
@@ -50,10 +52,18 @@ def get_internal_wsgi_application():
     if app_path is None:
         return get_wsgi_application()
 
-    return import_by_path(
-        app_path,
-        error_prefix="WSGI application '%s' could not be loaded; " % app_path
-    )
+    try:
+        return import_string(app_path)
+    except ImportError as e:
+        msg = (
+            "WSGI application '%(app_path)s' could not be loaded; "
+            "Error importing module: '%(exception)s'" % ({
+                'app_path': app_path,
+                'exception': e,
+            })
+        )
+        six.reraise(ImproperlyConfigured, ImproperlyConfigured(msg),
+                    sys.exc_info()[2])
 
 
 class ServerHandler(simple_server.ServerHandler, object):
diff --git a/django/core/signing.py b/django/core/signing.py
index 15b9eaec6e..17953af151 100644
--- a/django/core/signing.py
+++ b/django/core/signing.py
@@ -44,7 +44,7 @@ from django.conf import settings
 from django.utils import baseconv
 from django.utils.crypto import constant_time_compare, salted_hmac
 from django.utils.encoding import force_bytes, force_str, force_text
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 
 class BadSignature(Exception):
@@ -75,7 +75,7 @@ def base64_hmac(salt, value, key):
 
 
 def get_cookie_signer(salt='django.core.signing.get_cookie_signer'):
-    Signer = import_by_path(settings.SIGNING_BACKEND)
+    Signer = import_string(settings.SIGNING_BACKEND)
     return Signer('django.http.cookies' + settings.SECRET_KEY, salt=salt)
 
 
diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
index 949d2251e5..3e73744091 100644
--- a/django/db/migrations/state.py
+++ b/django/db/migrations/state.py
@@ -3,7 +3,7 @@ from django.apps.registry import Apps
 from django.db import models
 from django.db.models.options import DEFAULT_NAMES, normalize_unique_together
 from django.utils import six
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 
 class InvalidBasesError(ValueError):
@@ -115,7 +115,7 @@ class ModelState(object):
         fields = []
         for field in model._meta.local_fields:
             name, path, args, kwargs = field.deconstruct()
-            field_class = import_by_path(path)
+            field_class = import_string(path)
             try:
                 fields.append((name, field_class(*args, **kwargs)))
             except TypeError as e:
@@ -127,7 +127,7 @@ class ModelState(object):
                 ))
         for field in model._meta.local_many_to_many:
             name, path, args, kwargs = field.deconstruct()
-            field_class = import_by_path(path)
+            field_class = import_string(path)
             try:
                 fields.append((name, field_class(*args, **kwargs)))
             except TypeError as e:
@@ -175,7 +175,7 @@ class ModelState(object):
         fields = []
         for name, field in self.fields:
             _, path, args, kwargs = field.deconstruct()
-            field_class = import_by_path(path)
+            field_class = import_string(path)
             fields.append((name, field_class(*args, **kwargs)))
         # Now make a copy
         return self.__class__(
diff --git a/django/db/utils.py b/django/db/utils.py
index 0bcf33f252..51d2ffcba0 100644
--- a/django/db/utils.py
+++ b/django/db/utils.py
@@ -7,7 +7,7 @@ import warnings
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.utils.functional import cached_property
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils._os import upath
 from django.utils import six
 
@@ -221,7 +221,7 @@ class ConnectionRouter(object):
         routers = []
         for r in self._routers:
             if isinstance(r, six.string_types):
-                router = import_by_path(r)()
+                router = import_string(r)()
             else:
                 router = r
             routers.append(router)
diff --git a/django/template/context.py b/django/template/context.py
index 774f7af6b1..0f624ff8a6 100644
--- a/django/template/context.py
+++ b/django/template/context.py
@@ -1,5 +1,5 @@
 from copy import copy
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 
 # Cache of actual callables.
 _standard_context_processors = None
@@ -162,7 +162,7 @@ def get_standard_processors():
         collect.extend(_builtin_context_processors)
         collect.extend(settings.TEMPLATE_CONTEXT_PROCESSORS)
         for path in collect:
-            func = import_by_path(path)
+            func = import_string(path)
             processors.append(func)
         _standard_context_processors = tuple(processors)
     return _standard_context_processors
diff --git a/django/template/loader.py b/django/template/loader.py
index 1e18eecc02..e9e2172e4b 100644
--- a/django/template/loader.py
+++ b/django/template/loader.py
@@ -28,7 +28,7 @@
 from django.core.exceptions import ImproperlyConfigured
 from django.template.base import Origin, Template, Context, TemplateDoesNotExist
 from django.conf import settings
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils import six
 
 template_source_loaders = None
@@ -95,7 +95,7 @@ def find_template_loader(loader):
     else:
         args = []
     if isinstance(loader, six.string_types):
-        TemplateLoader = import_by_path(loader)
+        TemplateLoader = import_string(loader)
 
         if hasattr(TemplateLoader, 'load_template_source'):
             func = TemplateLoader(*args)
diff --git a/django/utils/log.py b/django/utils/log.py
index cf778b619b..f319704116 100644
--- a/django/utils/log.py
+++ b/django/utils/log.py
@@ -5,7 +5,7 @@ import warnings
 from django.conf import settings
 from django.core import mail
 from django.core.mail import get_connection
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.views.debug import ExceptionReporter, get_exception_reporter_filter
 
 # Imports kept for backwards-compatibility in Django 1.7.
@@ -73,7 +73,7 @@ def configure_logging(logging_config, logging_settings):
 
     if logging_config:
          # First find the logging configuration function ...
-        logging_config_func = import_by_path(logging_config)
+        logging_config_func = import_string(logging_config)
 
         logging_config_func(DEFAULT_LOGGING)
 
diff --git a/django/utils/module_loading.py b/django/utils/module_loading.py
index a6fe7aebcb..7ba0381307 100644
--- a/django/utils/module_loading.py
+++ b/django/utils/module_loading.py
@@ -5,33 +5,48 @@ import imp
 from importlib import import_module
 import os
 import sys
+import warnings
 
 from django.core.exceptions import ImproperlyConfigured
 from django.utils import six
 
 
-def import_by_path(dotted_path, error_prefix=''):
+def import_string(dotted_path):
     """
     Import a dotted module path and return the attribute/class designated by the
-    last name in the path. Raise ImproperlyConfigured if something goes wrong.
+    last name in the path. Raise ImportError if the import failed.
     """
     try:
         module_path, class_name = dotted_path.rsplit('.', 1)
     except ValueError:
-        raise ImproperlyConfigured("%s%s doesn't look like a module path" % (
-            error_prefix, dotted_path))
+        msg = "%s doesn't look like a module path" % dotted_path
+        six.reraise(ImportError, ImportError(msg), sys.exc_info()[2])
+
+    module = import_module(module_path)
+
     try:
-        module = import_module(module_path)
+        return getattr(module, class_name)
+    except AttributeError:
+        msg = 'Module "%s" does not define a "%s" attribute/class' % (
+            dotted_path, class_name)
+        six.reraise(ImportError, ImportError(msg), sys.exc_info()[2])
+
+
+def import_by_path(dotted_path, error_prefix=''):
+    """
+    Import a dotted module path and return the attribute/class designated by the
+    last name in the path. Raise ImproperlyConfigured if something goes wrong.
+    """
+    warnings.warn(
+        'import_by_path() has been deprecated. Use import_string() instead.',
+        PendingDeprecationWarning, stacklevel=2)
+    try:
+        attr = import_string(dotted_path)
     except ImportError as e:
         msg = '%sError importing module %s: "%s"' % (
-            error_prefix, module_path, e)
+            error_prefix, dotted_path, e)
         six.reraise(ImproperlyConfigured, ImproperlyConfigured(msg),
                     sys.exc_info()[2])
-    try:
-        attr = getattr(module, class_name)
-    except AttributeError:
-        raise ImproperlyConfigured('%sModule "%s" does not define a "%s" attribute/class' % (
-            error_prefix, module_path, class_name))
     return attr
 
 
diff --git a/django/views/debug.py b/django/views/debug.py
index 4f2097600f..d665c4e36b 100644
--- a/django/views/debug.py
+++ b/django/views/debug.py
@@ -14,7 +14,7 @@ from django.template.defaultfilters import force_escape, pprint
 from django.utils.datastructures import MultiValueDict
 from django.utils.html import escape
 from django.utils.encoding import force_bytes, smart_text
-from django.utils.module_loading import import_by_path
+from django.utils.module_loading import import_string
 from django.utils import six
 
 HIDDEN_SETTINGS = re.compile('API|TOKEN|KEY|SECRET|PASS|PROFANITIES_LIST|SIGNATURE')
@@ -85,7 +85,7 @@ def get_exception_reporter_filter(request):
     global default_exception_reporter_filter
     if default_exception_reporter_filter is None:
         # Load the default filter for the first time and cache it.
-        default_exception_reporter_filter = import_by_path(
+        default_exception_reporter_filter = import_string(
             settings.DEFAULT_EXCEPTION_REPORTER_FILTER)()
     if request:
         return getattr(request, 'exception_reporter_filter', default_exception_reporter_filter)