[lint package refactor] Create a file for check_parallel

2 files changed, 115 insertions, 104 deletions

diff --git a/pylint/lint/__init__.py b/pylint/lint/__init__.py
index e7001cdc6..009b1ae54 100644
--- a/pylint/lint/__init__.py
+++ b/pylint/lint/__init__.py
@@ -84,6 +84,7 @@ from pylint import (
 )
 from pylint.__pkginfo__ import version
 from pylint.constants import MAIN_CHECKER_NAME, MSG_TYPES
+from pylint.lint.check_parallel import check_parallel
 from pylint.lint.report_functions import (
     report_messages_by_module_stats,
     report_messages_stats,
@@ -95,7 +96,7 @@ from pylint.lint.utils import (
     fix_import_path,
     preprocess_options,
 )
-from pylint.message import Message, MessageDefinitionStore, MessagesHandlerMixIn
+from pylint.message import MessageDefinitionStore, MessagesHandlerMixIn
 from pylint.reporters.ureports import nodes as report_nodes
 from pylint.utils import ASTWalker, FileState, utils
 from pylint.utils.pragma_parser import (
@@ -120,37 +121,6 @@ def _read_stdin():
     return sys.stdin.read()
 
 
-def _get_new_args(message):
-    location = (
-        message.abspath,
-        message.path,
-        message.module,
-        message.obj,
-        message.line,
-        message.column,
-    )
-    return (message.msg_id, message.symbol, location, message.msg, message.confidence)
-
-
-def _merge_stats(stats):
-    merged = {}
-    by_msg = collections.Counter()
-    for stat in stats:
-        message_stats = stat.pop("by_msg", {})
-        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)
-            else:
-                merged[key] = merged[key] + item
-
-    merged["by_msg"] = by_msg
-    return merged
-
-
 # Python Linter class #########################################################
 
 MSGS = {
@@ -1290,78 +1260,6 @@ class PyLinter(
         return note
 
 
-def check_parallel(linter, jobs, files, arguments=None):
-    """Use the given linter to lint the files with given amount of workers (jobs)"""
-    # The reporter does not need to be passed to worker processess, i.e. the reporter does
-    # not need to be pickleable
-    original_reporter = linter.reporter
-    linter.reporter = None
-
-    # The linter is inherited by all the pool's workers, i.e. the linter
-    # is identical to the linter object here. This is requred so that
-    # a custom PyLinter object can be used.
-    initializer = functools.partial(_worker_initialize, arguments=arguments)
-    with multiprocessing.Pool(jobs, initializer=initializer, initargs=[linter]) as pool:
-        # ..and now when the workers have inherited the linter, the actual reporter
-        # can be set back here on the parent process so that results get stored into
-        # correct reporter
-        linter.set_reporter(original_reporter)
-        linter.open()
-
-        all_stats = []
-
-        for module, messages, stats, msg_status in pool.imap_unordered(
-            _worker_check_single_file, files
-        ):
-            linter.set_current_module(module)
-            for msg in messages:
-                msg = Message(*msg)
-                linter.reporter.handle_message(msg)
-
-            all_stats.append(stats)
-            linter.msg_status |= msg_status
-
-    linter.stats = _merge_stats(all_stats)
-
-    # Insert stats data to local checkers.
-    for checker in linter.get_checkers():
-        if checker is not linter:
-            checker.stats = linter.stats
-
-
-# PyLinter object used by worker processes when checking files using multiprocessing
-# should only be used by the worker processes
-_worker_linter = None
-
-
-def _worker_initialize(linter, arguments=None):
-    global _worker_linter  # pylint: disable=global-statement
-    _worker_linter = linter
-
-    # On the worker process side the messages are just collected and passed back to
-    # parent process as _worker_check_file function's return value
-    _worker_linter.set_reporter(reporters.CollectingReporter())
-    _worker_linter.open()
-
-    # Patch sys.path so that each argument is importable just like in single job mode
-    _patch_sys_path(arguments or ())
-
-
-def _worker_check_single_file(file_item):
-    name, filepath, modname = file_item
-
-    _worker_linter.open()
-    _worker_linter.check_single_file(name, filepath, modname)
-
-    msgs = [_get_new_args(m) for m in _worker_linter.reporter.messages]
-    return (
-        _worker_linter.current_name,
-        msgs,
-        _worker_linter.stats,
-        _worker_linter.msg_status,
-    )
-
-
 class Run:
     """helper class to use as main for pylint :
 
diff --git a/pylint/lint/check_parallel.py b/pylint/lint/check_parallel.py
new file mode 100644
index 000000000..6ac84c49f
--- /dev/null
+++ b/pylint/lint/check_parallel.py
@@ -0,0 +1,113 @@
+import collections
+import functools
+
+from pylint import reporters
+from pylint.lint.utils import _patch_sys_path
+from pylint.message import Message
+
+try:
+    import multiprocessing
+except ImportError:
+    multiprocessing = None  # type: ignore
+
+# PyLinter object used by worker processes when checking files using multiprocessing
+# should only be used by the worker processes
+_worker_linter = None
+
+
+def _get_new_args(message):
+    location = (
+        message.abspath,
+        message.path,
+        message.module,
+        message.obj,
+        message.line,
+        message.column,
+    )
+    return (message.msg_id, message.symbol, location, message.msg, message.confidence)
+
+
+def _merge_stats(stats):
+    merged = {}
+    by_msg = collections.Counter()
+    for stat in stats:
+        message_stats = stat.pop("by_msg", {})
+        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)
+            else:
+                merged[key] = merged[key] + item
+
+    merged["by_msg"] = by_msg
+    return merged
+
+
+def _worker_initialize(linter, arguments=None):
+    global _worker_linter  # pylint: disable=global-statement
+    _worker_linter = linter
+
+    # On the worker process side the messages are just collected and passed back to
+    # parent process as _worker_check_file function's return value
+    _worker_linter.set_reporter(reporters.CollectingReporter())
+    _worker_linter.open()
+
+    # Patch sys.path so that each argument is importable just like in single job mode
+    _patch_sys_path(arguments or ())
+
+
+def _worker_check_single_file(file_item):
+    name, filepath, modname = file_item
+
+    _worker_linter.open()
+    _worker_linter.check_single_file(name, filepath, modname)
+
+    msgs = [_get_new_args(m) for m in _worker_linter.reporter.messages]
+    return (
+        _worker_linter.current_name,
+        msgs,
+        _worker_linter.stats,
+        _worker_linter.msg_status,
+    )
+
+
+def check_parallel(linter, jobs, files, arguments=None):
+    """Use the given linter to lint the files with given amount of workers (jobs)"""
+    # The reporter does not need to be passed to worker processess, i.e. the reporter does
+    # not need to be pickleable
+    original_reporter = linter.reporter
+    linter.reporter = None
+
+    # The linter is inherited by all the pool's workers, i.e. the linter
+    # is identical to the linter object here. This is requred so that
+    # a custom PyLinter object can be used.
+    initializer = functools.partial(_worker_initialize, arguments=arguments)
+    with multiprocessing.Pool(jobs, initializer=initializer, initargs=[linter]) as pool:
+        # ..and now when the workers have inherited the linter, the actual reporter
+        # can be set back here on the parent process so that results get stored into
+        # correct reporter
+        linter.set_reporter(original_reporter)
+        linter.open()
+
+        all_stats = []
+
+        for module, messages, stats, msg_status in pool.imap_unordered(
+            _worker_check_single_file, files
+        ):
+            linter.set_current_module(module)
+            for msg in messages:
+                msg = Message(*msg)
+                linter.reporter.handle_message(msg)
+
+            all_stats.append(stats)
+            linter.msg_status |= msg_status
+
+    linter.stats = _merge_stats(all_stats)
+
+    # Insert stats data to local checkers.
+    for checker in linter.get_checkers():
+        if checker is not linter:
+            checker.stats = linter.stats