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node_modules/eslint/lib/rules/no-unsafe-optional-chaining.js

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+/**
+ * @fileoverview Rule to disallow unsafe optional chaining
+ * @author Yeon JuAn
+ */
+
+"use strict";
+
+const UNSAFE_ARITHMETIC_OPERATORS = new Set(["+", "-", "/", "*", "%", "**"]);
+const UNSAFE_ASSIGNMENT_OPERATORS = new Set(["+=", "-=", "/=", "*=", "%=", "**="]);
+const UNSAFE_RELATIONAL_OPERATORS = new Set(["in", "instanceof"]);
+
+/**
+ * Checks whether a node is a destructuring pattern or not
+ * @param {ASTNode} node node to check
+ * @returns {boolean} `true` if a node is a destructuring pattern, otherwise `false`
+ */
+function isDestructuringPattern(node) {
+    return node.type === "ObjectPattern" || node.type === "ArrayPattern";
+}
+
+module.exports = {
+    meta: {
+        type: "problem",
+
+        docs: {
+            description: "disallow use of optional chaining in contexts where the `undefined` value is not allowed",
+            category: "Possible Errors",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/no-unsafe-optional-chaining"
+        },
+        schema: [{
+            type: "object",
+            properties: {
+                disallowArithmeticOperators: {
+                    type: "boolean",
+                    default: false
+                }
+            },
+            additionalProperties: false
+        }],
+        fixable: null,
+        messages: {
+            unsafeOptionalChain: "Unsafe usage of optional chaining. If it short-circuits with 'undefined' the evaluation will throw TypeError.",
+            unsafeArithmetic: "Unsafe arithmetic operation on optional chaining. It can result in NaN."
+        }
+    },
+
+    create(context) {
+        const options = context.options[0] || {};
+        const disallowArithmeticOperators = (options.disallowArithmeticOperators) || false;
+
+        /**
+         * Reports unsafe usage of optional chaining
+         * @param {ASTNode} node node to report
+         * @returns {void}
+         */
+        function reportUnsafeUsage(node) {
+            context.report({
+                messageId: "unsafeOptionalChain",
+                node
+            });
+        }
+
+        /**
+         * Reports unsafe arithmetic operation on optional chaining
+         * @param {ASTNode} node node to report
+         * @returns {void}
+         */
+        function reportUnsafeArithmetic(node) {
+            context.report({
+                messageId: "unsafeArithmetic",
+                node
+            });
+        }
+
+        /**
+         * Checks and reports if a node can short-circuit with `undefined` by optional chaining.
+         * @param {ASTNode} [node] node to check
+         * @param {Function} reportFunc report function
+         * @returns {void}
+         */
+        function checkUndefinedShortCircuit(node, reportFunc) {
+            if (!node) {
+                return;
+            }
+            switch (node.type) {
+                case "LogicalExpression":
+                    if (node.operator === "||" || node.operator === "??") {
+                        checkUndefinedShortCircuit(node.right, reportFunc);
+                    } else if (node.operator === "&&") {
+                        checkUndefinedShortCircuit(node.left, reportFunc);
+                        checkUndefinedShortCircuit(node.right, reportFunc);
+                    }
+                    break;
+                case "SequenceExpression":
+                    checkUndefinedShortCircuit(
+                        node.expressions[node.expressions.length - 1],
+                        reportFunc
+                    );
+                    break;
+                case "ConditionalExpression":
+                    checkUndefinedShortCircuit(node.consequent, reportFunc);
+                    checkUndefinedShortCircuit(node.alternate, reportFunc);
+                    break;
+                case "AwaitExpression":
+                    checkUndefinedShortCircuit(node.argument, reportFunc);
+                    break;
+                case "ChainExpression":
+                    reportFunc(node);
+                    break;
+                default:
+                    break;
+            }
+        }
+
+        /**
+         * Checks unsafe usage of optional chaining
+         * @param {ASTNode} node node to check
+         * @returns {void}
+         */
+        function checkUnsafeUsage(node) {
+            checkUndefinedShortCircuit(node, reportUnsafeUsage);
+        }
+
+        /**
+         * Checks unsafe arithmetic operations on optional chaining
+         * @param {ASTNode} node node to check
+         * @returns {void}
+         */
+        function checkUnsafeArithmetic(node) {
+            checkUndefinedShortCircuit(node, reportUnsafeArithmetic);
+        }
+
+        return {
+            "AssignmentExpression, AssignmentPattern"(node) {
+                if (isDestructuringPattern(node.left)) {
+                    checkUnsafeUsage(node.right);
+                }
+            },
+            "ClassDeclaration, ClassExpression"(node) {
+                checkUnsafeUsage(node.superClass);
+            },
+            CallExpression(node) {
+                if (!node.optional) {
+                    checkUnsafeUsage(node.callee);
+                }
+            },
+            NewExpression(node) {
+                checkUnsafeUsage(node.callee);
+            },
+            VariableDeclarator(node) {
+                if (isDestructuringPattern(node.id)) {
+                    checkUnsafeUsage(node.init);
+                }
+            },
+            MemberExpression(node) {
+                if (!node.optional) {
+                    checkUnsafeUsage(node.object);
+                }
+            },
+            TaggedTemplateExpression(node) {
+                checkUnsafeUsage(node.tag);
+            },
+            ForOfStatement(node) {
+                checkUnsafeUsage(node.right);
+            },
+            SpreadElement(node) {
+                if (node.parent && node.parent.type !== "ObjectExpression") {
+                    checkUnsafeUsage(node.argument);
+                }
+            },
+            BinaryExpression(node) {
+                if (UNSAFE_RELATIONAL_OPERATORS.has(node.operator)) {
+                    checkUnsafeUsage(node.right);
+                }
+                if (
+                    disallowArithmeticOperators &&
+                    UNSAFE_ARITHMETIC_OPERATORS.has(node.operator)
+                ) {
+                    checkUnsafeArithmetic(node.right);
+                    checkUnsafeArithmetic(node.left);
+                }
+            },
+            WithStatement(node) {
+                checkUnsafeUsage(node.object);
+            },
+            UnaryExpression(node) {
+                if (
+                    disallowArithmeticOperators &&
+                    UNSAFE_ARITHMETIC_OPERATORS.has(node.operator)
+                ) {
+                    checkUnsafeArithmetic(node.argument);
+                }
+            },
+            AssignmentExpression(node) {
+                if (
+                    disallowArithmeticOperators &&
+                    UNSAFE_ASSIGNMENT_OPERATORS.has(node.operator)
+                ) {
+                    checkUnsafeArithmetic(node.right);
+                }
+            }
+        };
+    }
+};