Deprecate MapReduceMixin and implements its methods in BaseChecker

pylint/checkers/base_checker.py

@@ -11,6 +11,7 @@
 
 from astroid import nodes
 
+from pylint.checkers.mapreduce_checker import MapReduceMixin
 from pylint.config.arguments_provider import _ArgumentsProvider
 from pylint.constants import _MSG_ORDER, MAIN_CHECKER_NAME, WarningScope
 from pylint.exceptions import InvalidMessageError
@@ -24,7 +25,7 @@
 
 
 @functools.total_ordering
-class BaseChecker(_ArgumentsProvider):
+class BaseChecker(_ArgumentsProvider, MapReduceMixin):
 
     # checker name (you may reuse an existing one)
     name: str = ""
@@ -206,6 +207,12 @@ def open(self):
     def close(self):
         """Called after visiting project (i.e set of modules)."""
 
+    def get_map_data(self) -> Any:
+        return None
+
+    def reduce_map_data(self, linter: PyLinter, data: list[Any]) -> None:
+        return None
+
 
 class BaseTokenChecker(BaseChecker):
     """Base class for checkers that want to have access to the token stream."""

pylint/checkers/mapreduce_checker.py

@@ -2,16 +2,22 @@
 # For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
 # Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
 
+from __future__ import annotations
+
 import abc
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from pylint.lint import PyLinter
 
 
 class MapReduceMixin(metaclass=abc.ABCMeta):
     """A mixin design to allow multiprocess/threaded runs of a Checker."""
 
     @abc.abstractmethod
-    def get_map_data(self):
+    def get_map_data(self) -> Any:
         """Returns mergeable/reducible data that will be examined."""
 
     @abc.abstractmethod
-    def reduce_map_data(self, linter, data):
+    def reduce_map_data(self, linter: PyLinter, data: list[Any]) -> None:
         """For a given Checker, receives data for all mapped runs."""

pylint/checkers/similar.py

@@ -47,7 +47,7 @@
 import astroid
 from astroid import nodes
 
-from pylint.checkers import BaseChecker, MapReduceMixin, table_lines_from_stats
+from pylint.checkers import BaseChecker, table_lines_from_stats
 from pylint.interfaces import IRawChecker
 from pylint.reporters.ureports.nodes import Table
 from pylint.typing import Options
@@ -727,7 +727,7 @@ def report_similarities(
 
 
 # wrapper to get a pylint checker from the similar class
-class SimilarChecker(BaseChecker, Similar, MapReduceMixin):
+class SimilarChecker(BaseChecker, Similar):
     """Checks for similarities and duplicated code.
 
     This computation may be memory / CPU intensive, so you

pylint/lint/parallel.py

@@ -71,11 +71,9 @@ def _worker_check_single_file(
     _worker_linter.check_single_file_item(file_item)
     mapreduce_data = defaultdict(list)
     for checker in _worker_linter.get_checkers():
-        try:
-            data = checker.get_map_data()
-        except AttributeError:
-            continue
-        mapreduce_data[checker.name].append(data)
+        data = checker.get_map_data()
+        if data is not None:
+            mapreduce_data[checker.name].append(data)
     msgs = _worker_linter.reporter.messages
     assert isinstance(_worker_linter.reporter, reporters.CollectingReporter)
     _worker_linter.reporter.reset()
@@ -108,7 +106,7 @@ def _merge_mapreduce_data(
     # validation. The intent here is to collect all the mapreduce data for all checker-
     # runs across processes - that will then be passed to a static method on the
     # checkers to be reduced and further processed.
-    collated_map_reduce_data = defaultdict(list)
+    collated_map_reduce_data: defaultdict[str, list[Any]] = defaultdict(list)
     for linter_data in all_mapreduce_data.values():
         for run_data in linter_data:
             for checker_name, data in run_data.items():
@@ -132,8 +130,7 @@ def check_parallel(
     """Use the given linter to lint the files with given amount of workers (jobs).
 
     This splits the work filestream-by-filestream. If you need to do work across
-    multiple files, as in the similarity-checker, then inherit from MapReduceMixin and
-    implement the map/reduce mixin functionality.
+    multiple files, as in the similarity-checker, then implement the map/reduce mixin functionality.
     """
     # The linter is inherited by all the pool's workers, i.e. the linter
     # is identical to the linter object here. This is required so that

tests/test_check_parallel.py

@@ -19,7 +19,6 @@
 import pylint.interfaces
 import pylint.lint.parallel
 from pylint.checkers.base_checker import BaseChecker
-from pylint.checkers.mapreduce_checker import MapReduceMixin
 from pylint.lint import PyLinter
 from pylint.lint.parallel import _worker_check_single_file as worker_check_single_file
 from pylint.lint.parallel import _worker_initialize as worker_initialize
@@ -73,7 +72,7 @@ def process_module(self, _node: nodes.Module) -> None:
         self.data.append(record)
 
 
-class ParallelTestChecker(BaseChecker, MapReduceMixin):
+class ParallelTestChecker(BaseChecker):
     """A checker that does need to consolidate data.
 
     To simulate the need to consolidate data, this checker only