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qwen/nodejs/node_modules/eslint/lib/rules/no-sequences.js

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+/**
+ * @fileoverview Rule to flag use of comma operator
+ * @author Brandon Mills
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const DEFAULT_OPTIONS = {
+    allowInParentheses: true
+};
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Disallow comma operators",
+            recommended: false,
+            url: "https://eslint.org/docs/latest/rules/no-sequences"
+        },
+
+        schema: [{
+            properties: {
+                allowInParentheses: {
+                    type: "boolean",
+                    default: true
+                }
+            },
+            additionalProperties: false
+        }],
+
+        messages: {
+            unexpectedCommaExpression: "Unexpected use of comma operator."
+        }
+    },
+
+    create(context) {
+        const options = Object.assign({}, DEFAULT_OPTIONS, context.options[0]);
+        const sourceCode = context.sourceCode;
+
+        /**
+         * Parts of the grammar that are required to have parens.
+         */
+        const parenthesized = {
+            DoWhileStatement: "test",
+            IfStatement: "test",
+            SwitchStatement: "discriminant",
+            WhileStatement: "test",
+            WithStatement: "object",
+            ArrowFunctionExpression: "body"
+
+            /*
+             * Omitting CallExpression - commas are parsed as argument separators
+             * Omitting NewExpression - commas are parsed as argument separators
+             * Omitting ForInStatement - parts aren't individually parenthesised
+             * Omitting ForStatement - parts aren't individually parenthesised
+             */
+        };
+
+        /**
+         * Determines whether a node is required by the grammar to be wrapped in
+         * parens, e.g. the test of an if statement.
+         * @param {ASTNode} node The AST node
+         * @returns {boolean} True if parens around node belong to parent node.
+         */
+        function requiresExtraParens(node) {
+            return node.parent && parenthesized[node.parent.type] &&
+                    node === node.parent[parenthesized[node.parent.type]];
+        }
+
+        /**
+         * Check if a node is wrapped in parens.
+         * @param {ASTNode} node The AST node
+         * @returns {boolean} True if the node has a paren on each side.
+         */
+        function isParenthesised(node) {
+            return astUtils.isParenthesised(sourceCode, node);
+        }
+
+        /**
+         * Check if a node is wrapped in two levels of parens.
+         * @param {ASTNode} node The AST node
+         * @returns {boolean} True if two parens surround the node on each side.
+         */
+        function isParenthesisedTwice(node) {
+            const previousToken = sourceCode.getTokenBefore(node, 1),
+                nextToken = sourceCode.getTokenAfter(node, 1);
+
+            return isParenthesised(node) && previousToken && nextToken &&
+                astUtils.isOpeningParenToken(previousToken) && previousToken.range[1] <= node.range[0] &&
+                astUtils.isClosingParenToken(nextToken) && nextToken.range[0] >= node.range[1];
+        }
+
+        return {
+            SequenceExpression(node) {
+
+                // Always allow sequences in for statement update
+                if (node.parent.type === "ForStatement" &&
+                        (node === node.parent.init || node === node.parent.update)) {
+                    return;
+                }
+
+                // Wrapping a sequence in extra parens indicates intent
+                if (options.allowInParentheses) {
+                    if (requiresExtraParens(node)) {
+                        if (isParenthesisedTwice(node)) {
+                            return;
+                        }
+                    } else {
+                        if (isParenthesised(node)) {
+                            return;
+                        }
+                    }
+                }
+
+                const firstCommaToken = sourceCode.getTokenAfter(node.expressions[0], astUtils.isCommaToken);
+
+                context.report({ node, loc: firstCommaToken.loc, messageId: "unexpectedCommaExpression" });
+            }
+        };
+
+    }
+};