Move ``merge_stats`` to ``checkerstats.py``

3 files changed, 36 insertions, 25 deletions

diff --git a/pylint/lint/parallel.py b/pylint/lint/parallel.py
index 1896fc95f..b770b7bce 100644
--- a/pylint/lint/parallel.py
+++ b/pylint/lint/parallel.py
@@ -3,15 +3,13 @@
 
 import collections
 import functools
-from typing import TYPE_CHECKING, Any, DefaultDict, Dict, Iterable, List, Tuple, Union
+from typing import Any, DefaultDict, Iterable, List, Tuple
 
 from pylint import reporters
 from pylint.lint.utils import _patch_sys_path
 from pylint.message import Message
-from pylint.typing import CheckerStats, FileItem
-
-if TYPE_CHECKING:
-    from typing import Counter  # typing.Counter added in Python 3.6.1
+from pylint.typing import FileItem
+from pylint.utils import merge_stats
 
 try:
     import multiprocessing
@@ -35,25 +33,6 @@ def _get_new_args(message):
     return (message.msg_id, message.symbol, location, message.msg, message.confidence)
 
 
-def _merge_stats(stats: List[CheckerStats]):
-    merged: CheckerStats = {}
-    by_msg: "Counter[str]" = collections.Counter()
-    for stat in stats:
-        message_stats: Union["Counter[str]", Dict] = stat.pop("by_msg", {})  # type: ignore
-        by_msg.update(message_stats)
-
-        for key, item in stat.items():
-            if key not in merged:
-                merged[key] = item
-            elif isinstance(item, dict):
-                merged[key].update(item)  # type: ignore
-            else:
-                merged[key] = merged[key] + item  # type: ignore
-
-    merged["by_msg"] = by_msg
-    return merged
-
-
 def _worker_initialize(linter, arguments=None):
     global _worker_linter  # pylint: disable=global-statement
     _worker_linter = linter
@@ -167,7 +146,7 @@ def check_parallel(linter, jobs, files: Iterable[FileItem], arguments=None):
         pool.join()
 
     _merge_mapreduce_data(linter, all_mapreduce_data)
-    linter.stats = _merge_stats([linter.stats] + all_stats)
+    linter.stats = merge_stats([linter.stats] + all_stats)
 
     # Insert stats data to local checkers.
     for checker in linter.get_checkers():
diff --git a/pylint/utils/__init__.py b/pylint/utils/__init__.py
index 77cb08b76..a0658bf99 100644
--- a/pylint/utils/__init__.py
+++ b/pylint/utils/__init__.py
@@ -44,6 +44,7 @@ main pylint class
 """
 
 from pylint.utils.ast_walker import ASTWalker
+from pylint.utils.checkerstats import merge_stats
 from pylint.utils.file_state import FileState
 from pylint.utils.utils import (
     HAS_ISORT_5,
@@ -83,4 +84,5 @@ __all__ = [
     "normalize_text",
     "register_plugins",
     "tokenize_module",
+    "merge_stats",
 ]
diff --git a/pylint/utils/checkerstats.py b/pylint/utils/checkerstats.py
new file mode 100644
index 000000000..42af08167
--- /dev/null
+++ b/pylint/utils/checkerstats.py
@@ -0,0 +1,30 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+
+import collections
+from typing import TYPE_CHECKING, Dict, List, Union
+
+from pylint.typing import CheckerStats
+
+if TYPE_CHECKING:
+    from typing import Counter  # typing.Counter added in Python 3.6.1
+
+
+def merge_stats(stats: List[CheckerStats]):
+    """Used to merge two stats objects into a new one when pylint is run in parallel mode"""
+    merged: CheckerStats = {}
+    by_msg: "Counter[str]" = collections.Counter()
+    for stat in stats:
+        message_stats: Union["Counter[str]", Dict] = stat.pop("by_msg", {})  # type: ignore
+        by_msg.update(message_stats)
+
+        for key, item in stat.items():
+            if key not in merged:
+                merged[key] = item
+            elif isinstance(item, dict):
+                merged[key].update(item)  # type: ignore
+            else:
+                merged[key] = merged[key] + item  # type: ignore
+
+    merged["by_msg"] = by_msg
+    return merged