Fix two multiprocessing issues

doc/whatsnew/fragments/10037.bugfix

@@ -0,0 +1,3 @@
+Fix enabling checks from extensions which are disabled by default if multiple jobs are used.
+
+Closes #10037

doc/whatsnew/fragments/10642.bugfix

@@ -0,0 +1,3 @@
+Fix duplicate messages for extension checks if multiple jobs are used.
+
+Refs #10642

pylint/config/config_initialization.py

@@ -6,6 +6,7 @@
 
 import sys
 import warnings
+from copy import copy
 from glob import glob
 from itertools import chain
 from pathlib import Path
@@ -58,8 +59,12 @@ def _config_initialization(  # pylint: disable=too-many-statements
         exec(utils._unquote(config_data["init-hook"]))  # pylint: disable=exec-used
 
     # Load plugins if specified in the config file
+    default_checkers = copy(linter._registered_checkers)
     if "load-plugins" in config_data:
         linter.load_plugin_modules(utils._splitstrip(config_data["load-plugins"]))
+    linter._registered_dynamic_plugin_checkers = linter._registered_checkers.difference(
+        default_checkers
+    )
 
     unrecognized_options_message = None
     # First we parse any options from a configuration file

pylint/lint/parallel.py

@@ -54,6 +54,12 @@ def _worker_initialize(
 
     # Re-register dynamic plugins, since the pool does not have access to the
     # astroid module that existed when the linter was pickled.
+    # Freeze register new messages to prevent overwriting enabled and disabled messaged
+    # during dynamic plugin re-load.
+    _worker_linter._freeze_register_msgs = True
+    _worker_linter._deregister_checkers(
+        _worker_linter._registered_dynamic_plugin_checkers
+    )
     _worker_linter.load_plugin_modules(_worker_linter._dynamic_plugins, force=True)
     _worker_linter.load_plugin_configuration()
 

pylint/lint/pylinter.py

@@ -14,7 +14,7 @@
 import traceback
 import warnings
 from collections import defaultdict
-from collections.abc import Callable, Iterable, Iterator, Sequence
+from collections.abc import Callable, Collection, Iterable, Iterator, Sequence
 from io import TextIOWrapper
 from pathlib import Path
 from re import Pattern
@@ -323,6 +323,16 @@ def __init__(
         """Dictionary of registered and initialized checkers."""
         self._dynamic_plugins: dict[str, ModuleType | ModuleNotFoundError | bool] = {}
         """Set of loaded plugin names."""
+        self._registered_checkers: set[tuple[str, checkers.BaseChecker, int]] = set()
+        """Set of tuples with loaded checker name, reference to checker
+        and checker object id.
+        """
+        self._registered_dynamic_plugin_checkers: set[
+            tuple[str, checkers.BaseChecker, int]
+        ] = set()
+        """Set of tuples with loaded dynamic plugin checker name, reference to
+        checker and checker object id.
+        """
 
         # Attributes related to stats
         self.stats = LinterStats()
@@ -356,6 +366,7 @@ def __init__(
         self.msgs_store = MessageDefinitionStore(self.config.py_version)
         self.msg_status = 0
         self._by_id_managed_msgs: list[ManagedMessage] = []
+        self._freeze_register_msgs = False
 
         # Attributes related to visiting files
         self.file_state = FileState("", self.msgs_store, is_base_filestate=True)
@@ -495,17 +506,30 @@ def report_order(self) -> list[BaseChecker]:
     def register_checker(self, checker: checkers.BaseChecker) -> None:
         """This method auto registers the checker."""
         self._checkers[checker.name].append(checker)
+        self._registered_checkers.add((checker.name, checker, id(checker)))
         for r_id, r_title, r_cb in checker.reports:
             self.register_report(r_id, r_title, r_cb, checker)
-        if hasattr(checker, "msgs"):
+        if not self._freeze_register_msgs and hasattr(checker, "msgs"):
             self.msgs_store.register_messages_from_checker(checker)
             for message in checker.messages:
                 if not message.default_enabled:
                     self.disable(message.msgid)
         # Register the checker, but disable all of its messages.
-        if not getattr(checker, "enabled", True):
+        if not (self._freeze_register_msgs or getattr(checker, "enabled", True)):
             self.disable(checker.name)
 
+    def _deregister_checkers(
+        self, checker_collection: Collection[tuple[str, checkers.BaseChecker, int]]
+    ) -> None:
+        """De-registered a collection of checkers with its reports.
+
+        Leave messages in place as re-registering them is a no-op.
+        """
+        for checker_name, checker, _ in checker_collection:
+            self._checkers[checker_name].remove(checker)
+            if checker.reports:
+                self.deregister_reports(checker)
+
     def enable_fail_on_messages(self) -> None:
         """Enable 'fail on' msgs.
 

pylint/reporters/reports_handler_mix_in.py

@@ -48,6 +48,11 @@ def register_report(
         reportid = reportid.upper()
         self._reports[checker].append((reportid, r_title, r_cb))
 
+    def deregister_reports(self, checker: BaseChecker) -> None:
+        """De-register all reports for a checker."""
+        for r_id, r_title, r_cb in checker.reports:
+            self._reports[checker].remove((r_id, r_title, r_cb))
+
     def enable_report(self, reportid: str) -> None:
         """Enable the report of the given id."""
         reportid = reportid.upper()

tests/test_check_parallel.py

@@ -24,6 +24,7 @@
 import pylint.lint.parallel
 from pylint.checkers import BaseRawFileChecker
 from pylint.checkers.imports import ImportsChecker
+from pylint.config.config_initialization import _config_initialization
 from pylint.lint import PyLinter, augmented_sys_path
 from pylint.lint.parallel import _worker_check_single_file as worker_check_single_file
 from pylint.lint.parallel import _worker_initialize as worker_initialize
@@ -217,6 +218,59 @@ def test_worker_initialize_pickling(self) -> None:
         ) as executor:
             executor.map(print, [1, 2])
 
+    def test_worker_initialize_custom_plugins(self) -> None:
+        """Test plugins are initialized (only once) and messages are set to
+        enabled and disabled correctly, after the worker linter is initialized.
+        """
+        linter = PyLinter(reporter=Reporter())
+        linter.load_default_plugins()
+        config_data = {
+            "load-plugins": (
+                "pylint.extensions.code_style,"
+                "pylint.extensions.typing,"
+                "pylint.checkers.raw_metrics,"  # Custom report
+            ),
+        }
+        config_args = [
+            "--enable=consider-using-augmented-assign",
+            "--disable=consider-alternative-union-syntax",
+        ]
+        with patch(
+            "pylint.config.config_file_parser._ConfigurationFileParser.parse_config_file",
+            return_value=(config_data, config_args),
+        ):
+            _config_initialization(linter, [])
+        assert len(linter._checkers["code_style"]) == 1
+        assert len(linter._checkers["typing"]) == 1
+        assert len(linter._checkers["metrics"]) == 2
+        old_metrics_checker = linter._checkers["metrics"][-1]
+        assert len(linter._reports[old_metrics_checker]) == 2
+        assert linter.is_message_enabled("consider-using-augmented-assign") is True
+        assert (  # default disabled
+            linter.is_message_enabled("prefer-typing-namedtuple") is False
+        )
+        assert linter.is_message_enabled("consider-alternative-union-syntax") is False
+
+        worker_initialize(linter=dill.dumps(linter))
+        worker_linter = pylint.lint.parallel._worker_linter
+        assert isinstance(worker_linter, PyLinter)
+        assert len(worker_linter._registered_dynamic_plugin_checkers) == 3
+        assert len(worker_linter._checkers["code_style"]) == 1
+        assert len(worker_linter._checkers["typing"]) == 1
+        assert len(worker_linter._checkers["metrics"]) == 2
+        # The base checker overwrite __eq__ and __hash__ to only compare name and msgs.
+        # Thus, while the ids for the metrics checker are different, they have the same
+        # hash. That is used as key for the '_reports' dict.
+        new_metrics_checker = worker_linter._checkers["metrics"][-1]
+        assert id(old_metrics_checker) != id(new_metrics_checker)
+        assert old_metrics_checker == new_metrics_checker
+        assert len(worker_linter._reports[new_metrics_checker]) == 2
+        assert linter.is_message_enabled("consider-using-augmented-assign") is True
+        assert (  # default disabled
+            linter.is_message_enabled("prefer-typing-namedtuple") is False
+        )
+        assert linter.is_message_enabled("consider-alternative-union-syntax") is False
+
     def test_worker_check_single_file_uninitialised(self) -> None:
         pylint.lint.parallel._worker_linter = None
         with pytest.raises(  # Objects that do not match the linter interface will fail