Initial commit

venv/lib/python3.8/site-packages/pylint/extensions/comparetozero.py

@@ -0,0 +1,75 @@
+# Copyright (c) 2016 Alexander Todorov <atodorov@otb.bg>
+# Copyright (c) 2017-2018 Claudiu Popa <pcmanticore@gmail.com>
+# Copyright (c) 2019 Pierre Sassoulas <pierre.sassoulas@gmail.com>
+# Copyright (c) 2020 Anthony Sottile <asottile@umich.edu>
+
+# 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
+
+"""Looks for  comparisons to empty string."""
+
+import itertools
+
+import astroid
+
+from pylint import checkers, interfaces
+from pylint.checkers import utils
+
+
+def _is_constant_zero(node):
+    return isinstance(node, astroid.Const) and node.value == 0
+
+
+class CompareToZeroChecker(checkers.BaseChecker):
+    """Checks for comparisons to zero.
+    Most of the times 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!
+    """
+
+    __implements__ = (interfaces.IAstroidChecker,)
+
+    # configuration section name
+    name = "compare-to-zero"
+    msgs = {
+        "C2001": (
+            "Avoid comparisons to zero",
+            "compare-to-zero",
+            "Used when Pylint detects comparison to a 0 constant.",
+        )
+    }
+
+    priority = -2
+    options = ()
+
+    @utils.check_messages("compare-to-zero")
+    def visit_compare(self, node):
+        _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 = [("", node.left)]
+        ops.extend(node.ops)
+        ops = list(itertools.chain(*ops))
+
+        for ops_idx in range(len(ops) - 2):
+            op_1 = ops[ops_idx]
+            op_2 = ops[ops_idx + 1]
+            op_3 = ops[ops_idx + 2]
+            error_detected = False
+
+            # 0 ?? X
+            if _is_constant_zero(op_1) and op_2 in _operators:
+                error_detected = True
+            # X ?? 0
+            elif op_2 in _operators and _is_constant_zero(op_3):
+                error_detected = True
+
+            if error_detected:
+                self.add_message("compare-to-zero", node=node)
+
+
+def register(linter):
+    """Required method to auto register this checker."""
+    linter.register_checker(CompareToZeroChecker(linter))