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159 lines
5.5 KiB
159 lines
5.5 KiB
/**
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* @fileoverview Rule to flag assignment in a conditional statement's test expression
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* @author Stephen Murray <spmurrayzzz>
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("./utils/ast-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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const TEST_CONDITION_PARENT_TYPES = new Set(["IfStatement", "WhileStatement", "DoWhileStatement", "ForStatement", "ConditionalExpression"]);
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const NODE_DESCRIPTIONS = {
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DoWhileStatement: "a 'do...while' statement",
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ForStatement: "a 'for' statement",
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IfStatement: "an 'if' statement",
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WhileStatement: "a 'while' statement"
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};
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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/** @type {import('../shared/types').Rule} */
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module.exports = {
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meta: {
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type: "problem",
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docs: {
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description: "Disallow assignment operators in conditional expressions",
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recommended: true,
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url: "https://eslint.org/docs/latest/rules/no-cond-assign"
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},
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schema: [
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{
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enum: ["except-parens", "always"]
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}
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],
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messages: {
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unexpected: "Unexpected assignment within {{type}}.",
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// must match JSHint's error message
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missing: "Expected a conditional expression and instead saw an assignment."
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}
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},
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create(context) {
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const prohibitAssign = (context.options[0] || "except-parens");
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const sourceCode = context.sourceCode;
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/**
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* Check whether an AST node is the test expression for a conditional statement.
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* @param {!Object} node The node to test.
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* @returns {boolean} `true` if the node is the text expression for a conditional statement; otherwise, `false`.
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*/
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function isConditionalTestExpression(node) {
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return node.parent &&
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TEST_CONDITION_PARENT_TYPES.has(node.parent.type) &&
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node === node.parent.test;
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}
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/**
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* Given an AST node, perform a bottom-up search for the first ancestor that represents a conditional statement.
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* @param {!Object} node The node to use at the start of the search.
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* @returns {?Object} The closest ancestor node that represents a conditional statement.
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*/
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function findConditionalAncestor(node) {
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let currentAncestor = node;
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do {
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if (isConditionalTestExpression(currentAncestor)) {
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return currentAncestor.parent;
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}
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} while ((currentAncestor = currentAncestor.parent) && !astUtils.isFunction(currentAncestor));
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return null;
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}
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/**
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* Check whether the code represented by an AST node is enclosed in two sets of parentheses.
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* @param {!Object} node The node to test.
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* @returns {boolean} `true` if the code is enclosed in two sets of parentheses; otherwise, `false`.
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*/
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function isParenthesisedTwice(node) {
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const previousToken = sourceCode.getTokenBefore(node, 1),
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nextToken = sourceCode.getTokenAfter(node, 1);
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return astUtils.isParenthesised(sourceCode, node) &&
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previousToken && astUtils.isOpeningParenToken(previousToken) && previousToken.range[1] <= node.range[0] &&
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astUtils.isClosingParenToken(nextToken) && nextToken.range[0] >= node.range[1];
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}
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/**
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* Check a conditional statement's test expression for top-level assignments that are not enclosed in parentheses.
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* @param {!Object} node The node for the conditional statement.
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* @returns {void}
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*/
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function testForAssign(node) {
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if (node.test &&
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(node.test.type === "AssignmentExpression") &&
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(node.type === "ForStatement"
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? !astUtils.isParenthesised(sourceCode, node.test)
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: !isParenthesisedTwice(node.test)
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)
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) {
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context.report({
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node: node.test,
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messageId: "missing"
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});
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}
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}
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/**
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* Check whether an assignment expression is descended from a conditional statement's test expression.
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* @param {!Object} node The node for the assignment expression.
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* @returns {void}
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*/
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function testForConditionalAncestor(node) {
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const ancestor = findConditionalAncestor(node);
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if (ancestor) {
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context.report({
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node,
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messageId: "unexpected",
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data: {
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type: NODE_DESCRIPTIONS[ancestor.type] || ancestor.type
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}
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});
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}
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}
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if (prohibitAssign === "always") {
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return {
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AssignmentExpression: testForConditionalAncestor
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};
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}
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return {
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DoWhileStatement: testForAssign,
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ForStatement: testForAssign,
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IfStatement: testForAssign,
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WhileStatement: testForAssign,
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ConditionalExpression: testForAssign
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};
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}
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};
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