Switch from entrypoints to importlib_metadata

6 files changed, 33 insertions, 29 deletions

diff --git a/src/flake8/_compat.py b/src/flake8/_compat.py
new file mode 100644
index 0000000..85af0a3
--- /dev/null
+++ b/src/flake8/_compat.py
@@ -0,0 +1,14 @@
+"""Expose backports in a single place."""
+import sys
+
+if sys.version_info >= (3,):  # pragma: no cover (PY3+)
+    from functools import lru_cache
+else:  # pragma: no cover (<PY3)
+    from functools32 import lru_cache
+
+if sys.version_info >= (3, 8):  # pragma: no cover (PY38+)
+    import importlib.metadata as importlib_metadata
+else:  # pragma: no cover (<PY38)
+    import importlib_metadata
+
+__all__ = ("lru_cache", "importlib_metadata")
diff --git a/src/flake8/exceptions.py b/src/flake8/exceptions.py
index 53ca4b7..bef6f4b 100644
--- a/src/flake8/exceptions.py
+++ b/src/flake8/exceptions.py
@@ -1,10 +1,6 @@
 """Exception classes for all of Flake8."""
-
 from typing import Dict
 
-if False:  # `typing.TYPE_CHECKING` was introduced in 3.5.2
-    from flake8.plugins.manager import Plugin
-
 
 class Flake8Exception(Exception):
     """Plain Flake8 exception."""
@@ -23,18 +19,17 @@ class FailedToLoadPlugin(Flake8Exception):
 
     FORMAT = 'Flake8 failed to load plugin "%(name)s" due to %(exc)s.'
 
-    def __init__(self, plugin, exception):
-        # type: (Plugin, Exception) -> None
+    def __init__(self, plugin_name, exception):
+        # type: (str, Exception) -> None
         """Initialize our FailedToLoadPlugin exception."""
-        self.plugin = plugin
-        self.ep_name = self.plugin.name
+        self.plugin_name = plugin_name
         self.original_exception = exception
-        super(FailedToLoadPlugin, self).__init__(plugin, exception)
+        super(FailedToLoadPlugin, self).__init__(plugin_name, exception)
 
     def __str__(self):  # type: () -> str
         """Format our exception message."""
         return self.FORMAT % {
-            "name": self.ep_name,
+            "name": self.plugin_name,
             "exc": self.original_exception,
         }
 
diff --git a/src/flake8/main/application.py b/src/flake8/main/application.py
index 42e365f..a20c1d4 100644
--- a/src/flake8/main/application.py
+++ b/src/flake8/main/application.py
@@ -168,9 +168,7 @@ class Application(object):
 
         sys.path.extend(local_plugins.paths)
 
-        self.check_plugins = plugin_manager.Checkers(
-            local_plugins.extension
-        )
+        self.check_plugins = plugin_manager.Checkers(local_plugins.extension)
 
         self.formatting_plugins = plugin_manager.ReportFormatters(
             local_plugins.report
diff --git a/src/flake8/main/debug.py b/src/flake8/main/debug.py
index 1d56189..83a5a11 100644
--- a/src/flake8/main/debug.py
+++ b/src/flake8/main/debug.py
@@ -4,8 +4,7 @@ from __future__ import print_function
 import argparse
 import json
 import platform
-
-import entrypoints
+from typing import Dict, List
 
 
 class DebugAction(argparse.Action):
@@ -61,6 +60,6 @@ def plugins_from(option_manager):
     ]
 
 
-def dependencies():
+def dependencies():  # type: () -> List[Dict[str, str]]
     """Generate the list of dependencies we care about."""
-    return [{"dependency": "entrypoints", "version": entrypoints.__version__}]
+    return []
diff --git a/src/flake8/plugins/manager.py b/src/flake8/plugins/manager.py
index 75cc1ab..903a130 100644
--- a/src/flake8/plugins/manager.py
+++ b/src/flake8/plugins/manager.py
@@ -2,10 +2,9 @@
 import logging
 from typing import Any, Dict, List, Optional, Set
 
-import entrypoints
-
 from flake8 import exceptions
 from flake8 import utils
+from flake8._compat import importlib_metadata
 
 LOG = logging.getLogger(__name__)
 
@@ -159,7 +158,7 @@ class Plugin(object):
             except Exception as load_exception:
                 LOG.exception(load_exception)
                 failed_to_load = exceptions.FailedToLoadPlugin(
-                    plugin=self, exception=load_exception
+                    plugin_name=self.name, exception=load_exception
                 )
                 LOG.critical(str(failed_to_load))
                 raise failed_to_load
@@ -224,6 +223,7 @@ class PluginManager(object):  # pylint: disable=too-few-public-methods
     """Find and manage plugins consistently."""
 
     def __init__(self, namespace, local_plugins=None):
+        # type: (str, Optional[List[str]]) -> None
         """Initialize the manager.
 
         :param str namespace:
@@ -246,12 +246,16 @@ class PluginManager(object):  # pylint: disable=too-few-public-methods
         for plugin_str in local_plugins:
             name, _, entry_str = plugin_str.partition("=")
             name, entry_str = name.strip(), entry_str.strip()
-            entry_point = entrypoints.EntryPoint.from_string(entry_str, name)
+            entry_point = importlib_metadata.EntryPoint(name, entry_str, None)
             self._load_plugin_from_entrypoint(entry_point, local=True)
 
     def _load_entrypoint_plugins(self):
         LOG.info('Loading entry-points for "%s".', self.namespace)
-        for entry_point in entrypoints.get_group_all(self.namespace):
+        eps = importlib_metadata.entry_points().get(self.namespace, ())
+        # python2.7 occasionally gives duplicate results due to redundant
+        # `local/lib` -> `../lib` symlink on linux in virtualenvs so we
+        # eliminate duplicates here
+        for entry_point in sorted(frozenset(eps)):
             if entry_point.name == "per-file-ignores":
                 LOG.warning(
                     "flake8-per-file-ignores plugin is incompatible with "
diff --git a/src/flake8/style_guide.py b/src/flake8/style_guide.py
index ef9c6e9..9be0fe8 100644
--- a/src/flake8/style_guide.py
+++ b/src/flake8/style_guide.py
@@ -7,13 +7,13 @@ import enum
 import itertools
 import linecache
 import logging
-import sys
 from typing import Dict, Generator, List, Match, Optional, Sequence, Set
 from typing import Tuple, Union
 
 from flake8 import defaults
 from flake8 import statistics
 from flake8 import utils
+from flake8._compat import lru_cache
 from flake8.formatting import base as base_formatter
 
 __all__ = ("StyleGuide",)
@@ -21,12 +21,6 @@ __all__ = ("StyleGuide",)
 LOG = logging.getLogger(__name__)
 
 
-if sys.version_info < (3, 2):
-    from functools32 import lru_cache
-else:
-    from functools import lru_cache
-
-
 class Selected(enum.Enum):
     """Enum representing an explicitly or implicitly selected code."""