Merge the compare-to-zero extensions to 'implicit_booleaness_checker'

20 files changed, 147 insertions, 184 deletions

diff --git a/doc/data/messages/c/compare-to-zero/bad.py b/doc/data/messages/c/compare-to-zero/bad.py
deleted file mode 100644
index c987403a4..000000000
--- a/doc/data/messages/c/compare-to-zero/bad.py
+++ /dev/null
@@ -1,8 +0,0 @@
-x = 0
-y = 1
-
-if x == 0:  # [compare-to-zero]
-    print("x is equal to zero")
-
-if y != 0:  # [compare-to-zero]
-    print("y is not equal to zero")
diff --git a/doc/data/messages/c/compare-to-zero/good.py b/doc/data/messages/c/compare-to-zero/good.py
deleted file mode 100644
index bea3733e2..000000000
--- a/doc/data/messages/c/compare-to-zero/good.py
+++ /dev/null
@@ -1,8 +0,0 @@
-x = 0
-y = 1
-
-if not x:
-    print("x is equal to zero")
-
-if y:
-    print("y is not equal to zero")
diff --git a/doc/data/messages/c/compare-to-zero/pylintrc b/doc/data/messages/c/compare-to-zero/pylintrc
deleted file mode 100644
index 895291f84..000000000
--- a/doc/data/messages/c/compare-to-zero/pylintrc
+++ /dev/null
@@ -1,2 +0,0 @@
-[main]
-load-plugins=pylint.extensions.comparetozero
diff --git a/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/bad.py b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/bad.py
new file mode 100644
index 000000000..2f93afd31
--- /dev/null
+++ b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/bad.py
@@ -0,0 +1,6 @@
+def important_math(x: int, y: int) -> None:
+    if x == 0:  # [use-implicit-booleaness-not-comparison-to-zero]
+        print("x is equal to zero")
+
+    if y != 0:  # [use-implicit-booleaness-not-comparison-to-zero]
+        print("y is not equal to zero")
diff --git a/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/details.rst b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/details.rst
new file mode 100644
index 000000000..670633b2a
--- /dev/null
+++ b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/details.rst
@@ -0,0 +1,3 @@
+Following this check blindly in weakly typed code base can create hard to debug issues. If the value
+can be something else that is falsey but not an ``int`` (for example ``None``, or an empty string),
+the code will not be equivalent.
diff --git a/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/good.py b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/good.py
new file mode 100644
index 000000000..feae7fe30
--- /dev/null
+++ b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/good.py
@@ -0,0 +1,6 @@
+def important_math(x: int, y: int) -> None:
+    if not x:
+        print("x is equal to zero")
+
+    if y:
+        print("y is not equal to zero")
diff --git a/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/pylintrc b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/pylintrc
new file mode 100644
index 000000000..43d8bd751
--- /dev/null
+++ b/doc/data/messages/u/use-implicit-booleaness-not-comparison-to-zero/pylintrc
@@ -0,0 +1,2 @@
+[main]
+enable=use-implicit-booleaness-not-comparison-to-zero
diff --git a/doc/user_guide/checkers/extensions.rst b/doc/user_guide/checkers/extensions.rst
index 793b3889b..f3823d715 100644
--- a/doc/user_guide/checkers/extensions.rst
+++ b/doc/user_guide/checkers/extensions.rst
@@ -10,7 +10,6 @@ Pylint provides the following optional plugins:
 - :ref:`pylint.extensions.broad_try_clause`
 - :ref:`pylint.extensions.check_elif`
 - :ref:`pylint.extensions.code_style`
-- :ref:`pylint.extensions.comparetozero`
 - :ref:`pylint.extensions.comparison_placement`
 - :ref:`pylint.extensions.confusing_elif`
 - :ref:`pylint.extensions.consider_refactoring_into_while_condition`
@@ -102,20 +101,6 @@ Compare-To-Empty-String checker Messages
   Used when Pylint detects comparison to an empty string constant.
 
 
-.. _pylint.extensions.comparetozero:
-
-Compare-To-Zero checker
-~~~~~~~~~~~~~~~~~~~~~~~
-
-This checker is provided by ``pylint.extensions.comparetozero``.
-Verbatim name of the checker is ``compare-to-zero``.
-
-Compare-To-Zero checker Messages
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-:compare-to-zero (C2001): *"%s" can be simplified to "%s" as 0 is falsey*
-  Used when Pylint detects comparison to a 0 constant.
-
-
 .. _pylint.extensions.comparison_placement:
 
 Comparison-Placement checker
diff --git a/doc/user_guide/checkers/features.rst b/doc/user_guide/checkers/features.rst
index a6b08381a..e30aff544 100644
--- a/doc/user_guide/checkers/features.rst
+++ b/doc/user_guide/checkers/features.rst
@@ -893,6 +893,8 @@ Refactoring checker Messages
   Emitted when a single "return" or "return None" statement is found at the end
   of function or method definition. This statement can safely be removed
   because Python will implicitly return None
+:use-implicit-booleaness-not-comparison-to-zero (C1804): *"%s" can be simplified to "%s" as 0 is falsey*
+  Used when Pylint detects comparison to a 0 constant.
 :use-implicit-booleaness-not-comparison (C1803): *'%s' can be simplified to '%s' as an empty %s is falsey*
   Used when Pylint detects that collection literal comparison is being used to
   check for emptiness; Use implicit booleaness instead of a collection classes;
diff --git a/doc/user_guide/configuration/all-options.rst b/doc/user_guide/configuration/all-options.rst
index ecdfc9ef5..8ddafa104 100644
--- a/doc/user_guide/configuration/all-options.rst
+++ b/doc/user_guide/configuration/all-options.rst
@@ -233,7 +233,7 @@ Standard Checkers
 
    confidence = ["HIGH", "CONTROL_FLOW", "INFERENCE", "INFERENCE_FAILURE", "UNDEFINED"]
 
-   disable = ["raw-checker-failed", "bad-inline-option", "locally-disabled", "file-ignored", "suppressed-message", "useless-suppression", "deprecated-pragma", "use-symbolic-message-instead", "consider-using-augmented-assign"]
+   disable = ["raw-checker-failed", "bad-inline-option", "locally-disabled", "file-ignored", "suppressed-message", "useless-suppression", "deprecated-pragma", "use-implicit-booleaness-not-comparison-to-zero", "use-symbolic-message-instead", "consider-using-augmented-assign"]
 
    enable = []
 
diff --git a/doc/user_guide/messages/messages_overview.rst b/doc/user_guide/messages/messages_overview.rst
index 167802ae2..50f77d35e 100644
--- a/doc/user_guide/messages/messages_overview.rst
+++ b/doc/user_guide/messages/messages_overview.rst
@@ -391,7 +391,6 @@ All messages in the convention category:
    convention/bad-mcs-classmethod-argument
    convention/bad-mcs-method-argument
    convention/compare-to-empty-string
-   convention/compare-to-zero
    convention/consider-iterating-dictionary
    convention/consider-using-any-or-all
    convention/consider-using-dict-items
@@ -433,6 +432,7 @@ All messages in the convention category:
    convention/unnecessary-lambda-assignment
    convention/unneeded-not
    convention/use-implicit-booleaness-not-comparison
+   convention/use-implicit-booleaness-not-comparison-to-zero
    convention/use-implicit-booleaness-not-len
    convention/use-maxsplit-arg
    convention/use-sequence-for-iteration
@@ -449,6 +449,7 @@ All renamed messages in the convention category:
    :titlesonly:
 
    convention/blacklisted-name
+   convention/compare-to-zero
    convention/len-as-condition
    convention/missing-docstring
    convention/old-misplaced-comparison-constant
diff --git a/doc/whatsnew/fragments/6871.user_action b/doc/whatsnew/fragments/6871.user_action
new file mode 100644
index 000000000..9aceab4c1
--- /dev/null
+++ b/doc/whatsnew/fragments/6871.user_action
@@ -0,0 +1,12 @@
+* The compare to empty string checker (``pylint.extensions.emptystring``) has been removed and its checks are
+  now part of the implicit booleaness checker:
+
+  - ``compare-to-zero`` was renamed ``use-implicit-booleaness-not-comparison-to-zero``
+    and it now need to be enabled explicitly.
+  - The ``pylint.extensions.compare-to-zero`` extension no longer exists and
+    needs to be removed from the ``load-plugins`` option.
+
+This permits to make the likeness explicit and will provide better performance as they share most of their
+conditions to be raised.
+
+Refs #6871
diff --git a/pylint/checkers/refactoring/implicit_booleaness_checker.py b/pylint/checkers/refactoring/implicit_booleaness_checker.py
index 3215d7ecd..ff1a36205 100644
--- a/pylint/checkers/refactoring/implicit_booleaness_checker.py
+++ b/pylint/checkers/refactoring/implicit_booleaness_checker.py
@@ -4,6 +4,8 @@
 
 from __future__ import annotations
 
+import itertools
+
 import astroid
 from astroid import bases, nodes, util
 
@@ -12,6 +14,14 @@ from pylint.checkers import utils
 from pylint.interfaces import HIGH, INFERENCE
 
 
+def _is_constant_zero(node: str | nodes.NodeNG) -> bool:
+    # We have to check that node.value is not False because node.value == 0 is True
+    # when node.value is False
+    return (
+        isinstance(node, astroid.Const) and node.value == 0 and node.value is not False
+    )
+
+
 class ImplicitBooleanessChecker(checkers.BaseChecker):
     """Checks for incorrect usage of comparisons or len() inside conditions.
 
@@ -70,6 +80,12 @@ class ImplicitBooleanessChecker(checkers.BaseChecker):
             "used to check for emptiness; Use implicit booleaness instead "
             "of a collection classes; empty collections are considered as false",
         ),
+        "C1804": (
+            '"%s" can be simplified to "%s" as 0 is falsey',
+            "use-implicit-booleaness-not-comparison-to-zero",
+            "Used when Pylint detects comparison to a 0 constant.",
+            {"default_enabled": False, "old_names": [("C2001", "compare-to-zero")]},
+        ),
     }
 
     options = ()
@@ -149,6 +165,49 @@ class ImplicitBooleanessChecker(checkers.BaseChecker):
     @utils.only_required_for_messages("use-implicit-booleaness-not-comparison")
     def visit_compare(self, node: nodes.Compare) -> None:
         self._check_use_implicit_booleaness_not_comparison(node)
+        self._check_compare_to_zero(node)
+
+    @utils.only_required_for_messages("compare-to-zero")
+    def _check_compare_to_zero(self, node: nodes.Compare) -> None:
+        # pylint: disable=duplicate-code
+        _operators = ["!=", "==", "is not", "is"]
+        # note: astroid.Compare has the left most operand in node.left
+        # while the rest are a list of tuples in node.ops
+        # the format of the tuple is ('compare operator sign', node)
+        # here we squash everything into `ops` to make it easier for processing later
+        ops: list[tuple[str, nodes.NodeNG]] = [("", node.left)]
+        ops.extend(node.ops)
+        iter_ops = iter(ops)
+        all_ops = list(itertools.chain(*iter_ops))
+
+        for ops_idx in range(len(all_ops) - 2):
+            op_1 = all_ops[ops_idx]
+            op_2 = all_ops[ops_idx + 1]
+            op_3 = all_ops[ops_idx + 2]
+            error_detected = False
+
+            # 0 ?? X
+            if _is_constant_zero(op_1) and op_2 in _operators:
+                error_detected = True
+                op = op_3
+            # X ?? 0
+            elif op_2 in _operators and _is_constant_zero(op_3):
+                error_detected = True
+                op = op_1
+
+            if error_detected:
+                original = f"{op_1.as_string()} {op_2} {op_3.as_string()}"
+                suggestion = (
+                    op.as_string()
+                    if op_2 in {"!=", "is not"}
+                    else f"not {op.as_string()}"
+                )
+                self.add_message(
+                    "compare-to-zero",
+                    args=(original, suggestion),
+                    node=node,
+                    confidence=HIGH,
+                )
 
     def _check_use_implicit_booleaness_not_comparison(
         self, node: nodes.Compare
diff --git a/pylint/extensions/comparetozero.py b/pylint/extensions/comparetozero.py
deleted file mode 100644
index 0be821be3..000000000
--- a/pylint/extensions/comparetozero.py
+++ /dev/null
@@ -1,95 +0,0 @@
-# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
-# For details: https://github.com/pylint-dev/pylint/blob/main/LICENSE
-# Copyright (c) https://github.com/pylint-dev/pylint/blob/main/CONTRIBUTORS.txt
-
-"""Looks for comparisons to zero."""
-
-from __future__ import annotations
-
-import itertools
-from typing import TYPE_CHECKING
-
-import astroid
-from astroid import nodes
-
-from pylint import checkers
-from pylint.checkers import utils
-from pylint.interfaces import HIGH
-
-if TYPE_CHECKING:
-    from pylint.lint import PyLinter
-
-
-def _is_constant_zero(node: str | nodes.NodeNG) -> bool:
-    # We have to check that node.value is not False because node.value == 0 is True
-    # when node.value is False
-    return (
-        isinstance(node, astroid.Const) and node.value == 0 and node.value is not False
-    )
-
-
-class CompareToZeroChecker(checkers.BaseChecker):
-    """Checks for comparisons to zero.
-
-    Most of the time you should use the fact that integers with a value of 0 are false.
-    An exception to this rule is when 0 is allowed in the program and has a
-    different meaning than None!
-    """
-
-    # configuration section name
-    name = "compare-to-zero"
-    msgs = {
-        "C2001": (
-            '"%s" can be simplified to "%s" as 0 is falsey',
-            "compare-to-zero",
-            "Used when Pylint detects comparison to a 0 constant.",
-        )
-    }
-
-    options = ()
-
-    @utils.only_required_for_messages("compare-to-zero")
-    def visit_compare(self, node: nodes.Compare) -> None:
-        # pylint: disable=duplicate-code
-        _operators = ["!=", "==", "is not", "is"]
-        # note: astroid.Compare has the left most operand in node.left
-        # while the rest are a list of tuples in node.ops
-        # the format of the tuple is ('compare operator sign', node)
-        # here we squash everything into `ops` to make it easier for processing later
-        ops: list[tuple[str, nodes.NodeNG]] = [("", node.left)]
-        ops.extend(node.ops)
-        iter_ops = iter(ops)
-        all_ops = list(itertools.chain(*iter_ops))
-
-        for ops_idx in range(len(all_ops) - 2):
-            op_1 = all_ops[ops_idx]
-            op_2 = all_ops[ops_idx + 1]
-            op_3 = all_ops[ops_idx + 2]
-            error_detected = False
-
-            # 0 ?? X
-            if _is_constant_zero(op_1) and op_2 in _operators:
-                error_detected = True
-                op = op_3
-            # X ?? 0
-            elif op_2 in _operators and _is_constant_zero(op_3):
-                error_detected = True
-                op = op_1
-
-            if error_detected:
-                original = f"{op_1.as_string()} {op_2} {op_3.as_string()}"
-                suggestion = (
-                    op.as_string()
-                    if op_2 in {"!=", "is not"}
-                    else f"not {op.as_string()}"
-                )
-                self.add_message(
-                    "compare-to-zero",
-                    args=(original, suggestion),
-                    node=node,
-                    confidence=HIGH,
-                )
-
-
-def register(linter: PyLinter) -> None:
-    linter.register_checker(CompareToZeroChecker(linter))
diff --git a/tests/functional/ext/comparetozero/compare_to_zero.py b/tests/functional/ext/comparetozero/compare_to_zero.py
deleted file mode 100644
index 6a14b8bc9..000000000
--- a/tests/functional/ext/comparetozero/compare_to_zero.py
+++ /dev/null
@@ -1,46 +0,0 @@
-# pylint: disable=literal-comparison,missing-docstring, singleton-comparison
-
-X = 123
-Y = len('test')
-
-if X is 0:  # [compare-to-zero]
-    pass
-
-if X is False:
-    pass
-
-if Y is not 0:  # [compare-to-zero]
-    pass
-
-if Y is not False:
-    pass
-
-if X == 0:  # [compare-to-zero]
-    pass
-
-if X == False:
-    pass
-
-if 0 == Y:  # [compare-to-zero]
-    pass
-
-if Y != 0:  # [compare-to-zero]
-    pass
-
-if 0 != X:  # [compare-to-zero]
-    pass
-
-if Y != False:
-    pass
-
-if X > 0:
-    pass
-
-if X < 0:
-    pass
-
-if 0 < X:
-    pass
-
-if 0 > X:
-    pass
diff --git a/tests/functional/ext/comparetozero/compare_to_zero.rc b/tests/functional/ext/comparetozero/compare_to_zero.rc
deleted file mode 100644
index 70c6171b5..000000000
--- a/tests/functional/ext/comparetozero/compare_to_zero.rc
+++ /dev/null
@@ -1,2 +0,0 @@
-[MAIN]
-load-plugins=pylint.extensions.comparetozero,
diff --git a/tests/functional/ext/comparetozero/compare_to_zero.txt b/tests/functional/ext/comparetozero/compare_to_zero.txt
deleted file mode 100644
index a413a3268..000000000
--- a/tests/functional/ext/comparetozero/compare_to_zero.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-compare-to-zero:6:3:6:9::"""X is 0"" can be simplified to ""not X"" as 0 is falsey":HIGH
-compare-to-zero:12:3:12:13::"""Y is not 0"" can be simplified to ""Y"" as 0 is falsey":HIGH
-compare-to-zero:18:3:18:9::"""X == 0"" can be simplified to ""not X"" as 0 is falsey":HIGH
-compare-to-zero:24:3:24:9::"""0 == Y"" can be simplified to ""not Y"" as 0 is falsey":HIGH
-compare-to-zero:27:3:27:9::"""Y != 0"" can be simplified to ""Y"" as 0 is falsey":HIGH
-compare-to-zero:30:3:30:9::"""0 != X"" can be simplified to ""X"" as 0 is falsey":HIGH
diff --git a/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.py b/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.py
new file mode 100644
index 000000000..766b1f547
--- /dev/null
+++ b/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.py
@@ -0,0 +1,46 @@
+# pylint: disable=literal-comparison,missing-docstring, singleton-comparison
+
+X = 123
+Y = len('test')
+
+if X is 0:  # [use-implicit-booleaness-not-comparison-to-zero]
+    pass
+
+if X is False:
+    pass
+
+if Y is not 0:  # [use-implicit-booleaness-not-comparison-to-zero]
+    pass
+
+if Y is not False:
+    pass
+
+if X == 0:  # [use-implicit-booleaness-not-comparison-to-zero]
+    pass
+
+if X == False:
+    pass
+
+if 0 == Y:  # [use-implicit-booleaness-not-comparison-to-zero]
+    pass
+
+if Y != 0:  # [use-implicit-booleaness-not-comparison-to-zero]
+    pass
+
+if 0 != X:  # [use-implicit-booleaness-not-comparison-to-zero]
+    pass
+
+if Y != False:
+    pass
+
+if X > 0:
+    pass
+
+if X < 0:
+    pass
+
+if 0 < X:
+    pass
+
+if 0 > X:
+    pass
diff --git a/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.rc b/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.rc
new file mode 100644
index 000000000..be01705b1
--- /dev/null
+++ b/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.rc
@@ -0,0 +1,2 @@
+[MAIN]
+enable=compare-to-zero,
diff --git a/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.txt b/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.txt
new file mode 100644
index 000000000..25702682a
--- /dev/null
+++ b/tests/functional/u/use/use_implicit_booleaness_not_comparison_to_zero.txt
@@ -0,0 +1,6 @@
+use-implicit-booleaness-not-comparison-to-zero:6:3:6:9::"""X is 0"" can be simplified to ""not X"" as 0 is falsey":HIGH
+use-implicit-booleaness-not-comparison-to-zero:12:3:12:13::"""Y is not 0"" can be simplified to ""Y"" as 0 is falsey":HIGH
+use-implicit-booleaness-not-comparison-to-zero:18:3:18:9::"""X == 0"" can be simplified to ""not X"" as 0 is falsey":HIGH
+use-implicit-booleaness-not-comparison-to-zero:24:3:24:9::"""0 == Y"" can be simplified to ""not Y"" as 0 is falsey":HIGH
+use-implicit-booleaness-not-comparison-to-zero:27:3:27:9::"""Y != 0"" can be simplified to ""Y"" as 0 is falsey":HIGH
+use-implicit-booleaness-not-comparison-to-zero:30:3:30:9::"""0 != X"" can be simplified to ""X"" as 0 is falsey":HIGH