Add `consider-refactoring-into-while-condition` checker (#8021)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>
Co-authored-by: Mark Byrne <31762852+mbyrnepr2@users.noreply.github.com>
Co-authored-by: Jacob Walls <jacobtylerwalls@gmail.com>

1 files changed, 93 insertions, 0 deletions

diff --git a/pylint/extensions/consider_refactoring_into_while_condition.py b/pylint/extensions/consider_refactoring_into_while_condition.py
new file mode 100644
index 000000000..b4b53d8fa
--- /dev/null
+++ b/pylint/extensions/consider_refactoring_into_while_condition.py
@@ -0,0 +1,93 @@
+# 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
+# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
+
+"""Looks for try/except statements with too much code in the try clause."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+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
+
+
+class ConsiderRefactorIntoWhileConditionChecker(checkers.BaseChecker):
+    """Checks for instances where while loops are implemented with a constant condition
+    which.
+
+    always evaluates to truthy and the first statement(s) is/are if statements which, when
+    evaluated.
+
+    to True, breaks out of the loop.
+
+    The if statement(s) can be refactored into the while loop.
+    """
+
+    name = "consider_refactoring_into_while"
+    msgs = {
+        "R3501": (
+            "Consider using 'while %s' instead of 'while %s:' an 'if', and a 'break'",
+            "consider-refactoring-into-while-condition",
+            "Emitted when `while True:` loop is used and the first statement is a break condition. "
+            "The ``if / break`` construct can be removed if the check is inverted and moved to "
+            "the ``while`` statement.",
+        ),
+    }
+
+    @utils.only_required_for_messages("consider-refactoring-into-while-condition")
+    def visit_while(self, node: nodes.While) -> None:
+        self._check_breaking_after_while_true(node)
+
+    def _check_breaking_after_while_true(self, node: nodes.While) -> None:
+        """Check that any loop with an ``if`` clause has a break statement."""
+        if not isinstance(node.test, nodes.Const) or not node.test.bool_value():
+            return
+        pri_candidates: list[nodes.If] = []
+        for n in node.body:
+            if not isinstance(n, nodes.If):
+                break
+            pri_candidates.append(n)
+        candidates = []
+        tainted = False
+        for c in pri_candidates:
+            if tainted or not isinstance(c.body[0], nodes.Break):
+                break
+            candidates.append(c)
+            orelse = c.orelse
+            while orelse:
+                orelse_node = orelse[0]
+                if not isinstance(orelse_node, nodes.If):
+                    tainted = True
+                else:
+                    candidates.append(orelse_node)
+                if not isinstance(orelse_node, nodes.If):
+                    break
+                orelse = orelse_node.orelse
+
+        candidates = [n for n in candidates if isinstance(n.body[0], nodes.Break)]
+        msg = " and ".join(
+            [f"({utils.not_condition_as_string(c.test)})" for c in candidates]
+        )
+        if len(candidates) == 1:
+            msg = utils.not_condition_as_string(candidates[0].test)
+        if not msg:
+            return
+
+        self.add_message(
+            "consider-refactoring-into-while-condition",
+            node=node,
+            line=node.lineno,
+            args=(msg, node.test.as_string()),
+            confidence=HIGH,
+        )
+
+
+def register(linter: PyLinter) -> None:
+    linter.register_checker(ConsiderRefactorIntoWhileConditionChecker(linter))