Refactor file checking to allow parallel linting in Prospector

CONTRIBUTORS.txt

@@ -339,3 +339,4 @@ contributors:
 
 * laike9m: contributor
 
+* Janne Rönkkö: contributor

ChangeLog

@@ -31,11 +31,21 @@ Release date: TBA
 
   Closes #2729
 
+* Allow parallel linting when run under Prospector
+
 
 What's New in Pylint 2.4.3?
 ===========================
 
-Release date: TBA
+  Pass the actual PyLinter object to sub processes to allow using custom
+  PyLinter classes.
+
+  PyLinter object (and all its members except reporter) needs to support
+  pickling so the PyLinter object can be passed to worker processes.
+
+* Refactor file checking
+
+  Remove code duplication from file checking.
 
 * Fix an issue with ``unnecessary-comprehension`` in comprehensions with additional repacking of elements.
 

pylint/checkers/classes.py

@@ -634,11 +634,15 @@ def _has_same_layout_slots(slots, assigned_value):
 }
 
 
+def _scope_default():
+    return collections.defaultdict(list)
+
+
 class ScopeAccessMap:
     """Store the accessed variables per scope."""
 
     def __init__(self):
-        self._scopes = collections.defaultdict(lambda: collections.defaultdict(list))
+        self._scopes = collections.defaultdict(_scope_default)
 
     def set_accessed(self, node):
         """Set the given node as accessed."""

pylint/config.py

@@ -37,6 +37,7 @@
 import configparser
 import contextlib
 import copy
+import functools
 import io
 import optparse
 import os
@@ -719,10 +720,8 @@ def read_config_file(self, config_file=None, verbose=None):
             opt = "-".join(["long"] * helplevel) + "-help"
             if opt in self._all_options:
                 break  # already processed
-            # pylint: disable=unused-argument
-            def helpfunc(option, opt, val, p, level=helplevel):
-                print(self.help(level))
-                sys.exit(0)
+
+            helpfunc = functools.partial(self.helpfunc, level=helplevel)
 
             helpmsg = "%s verbose help." % " ".join(["more"] * helplevel)
             optdict = {"action": "callback", "callback": helpfunc, "help": helpmsg}
@@ -830,6 +829,10 @@ def help(self, level=0):
         with _patch_optparse():
             return self.cmdline_parser.format_help()
 
+    def helpfunc(self, option, opt, val, p, level):  # pylint: disable=unused-argument
+        print(self.help(level))
+        sys.exit(0)
+
 
 class OptionsProviderMixIn:
     """Mixin to provide options to an OptionsManager"""