Add new consider-using-generator checker Issue #3165

CONTRIBUTORS.txt

@@ -446,4 +446,7 @@ contributors:
 
 * David Gilman: contributor
 
+* Ikraduya Edian: contributor
+    - Added new checks 'consider-using-generator' and 'use-a-generator'.
+
 * Tiago Honorato: contributor

ChangeLog

@@ -168,8 +168,17 @@ What's New in Pylint 2.7.0?
 
   Close #3555
 
+* New check: ``consider-using-generator``
+
+  This check warns when a comprehension is used inside an `any` or `all` function,
+  since it is unnecessary and should be replaced by a generator instead.
+  Using a generator would be less code and way faster.
+
+  Close #3165
+
 * Add Github Actions to replace Travis and AppVeyor in the future
 
+
 What's New in Pylint 2.6.1?
 ===========================
 

doc/whatsnew/2.7.rst

@@ -26,6 +26,8 @@ New checkers
 
 * Add `condition-evals-to-constant` check for conditionals using and/or that evaluate to a constant.
 
+* Add `consider-using-generator` check for the use of list comprehension inside ``any`` or ``all`` function.
+
 Other Changes
 =============
 

pylint/checkers/refactoring/refactoring_checker.py

@@ -1,4 +1,22 @@
 # -*- coding: utf-8 -*-
+# Copyright (c) 2016-2018 Claudiu Popa <[email protected]>
+# Copyright (c) 2016-2017 Łukasz Rogalski <[email protected]>
+# Copyright (c) 2016 Moises Lopez <[email protected]>
+# Copyright (c) 2016 Alexander Todorov <[email protected]>
+# Copyright (c) 2017-2018 hippo91 <[email protected]>
+# Copyright (c) 2017 Ville Skyttä <[email protected]>
+# Copyright (c) 2017-2018 Bryce Guinta <[email protected]>
+# Copyright (c) 2017 Hugo <[email protected]>
+# Copyright (c) 2017 Łukasz Sznuk <[email protected]>
+# Copyright (c) 2017 Alex Hearn <[email protected]>
+# Copyright (c) 2017 Antonio Ossa <[email protected]>
+# Copyright (c) 2018 Konstantin Manna <[email protected]>
+# Copyright (c) 2018 Konstantin <[email protected]>
+# Copyright (c) 2018 Sushobhit <[email protected]>
+# Copyright (c) 2018 Matej Marušák <[email protected]>
+# Copyright (c) 2018 Ville Skyttä <[email protected]>
+# Copyright (c) 2018 Mr. Senko <[email protected]>
+# Copyright (c) 2019 Ikraduya Edian <[email protected]>
 
 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 # For details: https://github.com/PyCQA/pylint/blob/master/COPYING
@@ -282,6 +300,18 @@ class RefactoringChecker(checkers.BaseTokenChecker):
             "Emitted when calling the super() builtin with the current class "
             "and instance. On Python 3 these arguments are the default and they can be omitted.",
         ),
+        "R1728": (
+            "Consider using a generator instead '%s(%s)'",
+            "consider-using-generator",
+            "If your container can be large using "
+            "a generator will bring better performance.",
+        ),
+        "R1729": (
+            "Use a generator instead '%s(%s)'",
+            "use-a-generator",
+            "Comprehension inside of 'any' or 'all' is unnecessary. "
+            "A generator would be sufficient and faster.",
+        ),
     }
     options = (
         (
@@ -684,18 +714,49 @@ def _check_consider_using_comprehension_constructor(self, node):
                 message_name = "consider-using-set-comprehension"
                 self.add_message(message_name, node=node)
 
+    def _check_consider_using_generator(self, node):
+        # 'any' and 'all' definitely should use generator, while 'list' and 'tuple' need to be considered first
+        # See https://github.com/PyCQA/pylint/pull/3309#discussion_r576683109
+        checked_call = ["any", "all", "list", "tuple"]
+        if (
+            isinstance(node, astroid.Call)
+            and node.func
+            and isinstance(node.func, astroid.Name)
+            and node.func.name in checked_call
+        ):
+            # functions in checked_calls take exactly one argument
+            # check whether the argument is list comprehension
+            if len(node.args) == 1 and isinstance(node.args[0], astroid.ListComp):
+                # remove square brackets '[]'
+                inside_comp = node.args[0].as_string()[1:-1]
+                call_name = node.func.name
+                if call_name in ["any", "all"]:
+                    self.add_message(
+                        "use-a-generator",
+                        node=node,
+                        args=(call_name, inside_comp),
+                    )
+                else:
+                    self.add_message(
+                        "consider-using-generator",
+                        node=node,
+                        args=(call_name, inside_comp),
+                    )
+
     @utils.check_messages(
         "stop-iteration-return",
         "consider-using-dict-comprehension",
         "consider-using-set-comprehension",
         "consider-using-sys-exit",
         "super-with-arguments",
+        "consider-using-generator",
     )
     def visit_call(self, node):
         self._check_raising_stopiteration_in_generator_next_call(node)
         self._check_consider_using_comprehension_constructor(node)
         self._check_quit_exit_call(node)
         self._check_super_with_arguments(node)
+        self._check_consider_using_generator(node)
 
     @staticmethod
     def _has_exit_in_scope(scope):

tests/functional/c/consider_using_generator.py

@@ -0,0 +1,11 @@
+# pylint: disable=missing-docstring, invalid-name
+# https://github.com/PyCQA/pylint/issues/3165
+
+list([])
+tuple([])
+
+list([0 for y in list(range(10))]) # [consider-using-generator]
+tuple([0 for y in list(range(10))]) # [consider-using-generator]
+
+list(0 for y in list(range(10)))
+tuple(0 for y in list(range(10)))

tests/functional/c/consider_using_generator.txt

@@ -0,0 +1,2 @@
+consider-using-generator:7:0::Consider using a generator instead 'list(0 for y in list(range(10)))'
+consider-using-generator:8:0::Consider using a generator instead 'tuple(0 for y in list(range(10)))'

tests/functional/u/use_a_generator.py

@@ -0,0 +1,11 @@
+# pylint: disable=missing-docstring, invalid-name
+# https://github.com/PyCQA/pylint/issues/3165
+
+any([])
+all([])
+
+any([0 for x in list(range(10))]) # [use-a-generator]
+all([0 for y in list(range(10))]) # [use-a-generator]
+
+any(0 for x in list(range(10)))
+all(0 for y in list(range(10)))

tests/functional/u/use_a_generator.txt

@@ -0,0 +1,2 @@
+use-a-generator:7:0::Use a generator instead 'any(0 for x in list(range(10)))'
+use-a-generator:8:0::Use a generator instead 'all(0 for y in list(range(10)))'