/** * @fileoverview Rule to flag use constant conditions * @author Christian Schulz */ "use strict"; const { isConstant } = require("./utils/ast-utils"); //------------------------------------------------------------------------------ // Helpers //------------------------------------------------------------------------------ //------------------------------------------------------------------------------ // Rule Definition //------------------------------------------------------------------------------ /** @type {import('../types').Rule.RuleModule} */ module.exports = { meta: { type: "problem", defaultOptions: [{ checkLoops: "allExceptWhileTrue" }], docs: { description: "Disallow constant expressions in conditions", recommended: true, url: "https://eslint.org/docs/latest/rules/no-constant-condition", }, schema: [ { type: "object", properties: { checkLoops: { enum: [ "all", "allExceptWhileTrue", "none", true, false, ], }, }, additionalProperties: false, }, ], messages: { unexpected: "Unexpected constant condition.", }, }, create(context) { const loopSetStack = []; const sourceCode = context.sourceCode; let [{ checkLoops }] = context.options; if (checkLoops === true) { checkLoops = "all"; } else if (checkLoops === false) { checkLoops = "none"; } let loopsInCurrentScope = new Set(); //-------------------------------------------------------------------------- // Helpers //-------------------------------------------------------------------------- /** * Tracks when the given node contains a constant condition. * @param {ASTNode} node The AST node to check. * @returns {void} * @private */ function trackConstantConditionLoop(node) { if ( node.test && isConstant(sourceCode.getScope(node), node.test, true) ) { loopsInCurrentScope.add(node); } } /** * Reports when the set contains the given constant condition node * @param {ASTNode} node The AST node to check. * @returns {void} * @private */ function checkConstantConditionLoopInSet(node) { if (loopsInCurrentScope.has(node)) { loopsInCurrentScope.delete(node); context.report({ node: node.test, messageId: "unexpected" }); } } /** * Reports when the given node contains a constant condition. * @param {ASTNode} node The AST node to check. * @returns {void} * @private */ function reportIfConstant(node) { if ( node.test && isConstant(sourceCode.getScope(node), node.test, true) ) { context.report({ node: node.test, messageId: "unexpected" }); } } /** * Stores current set of constant loops in loopSetStack temporarily * and uses a new set to track constant loops * @returns {void} * @private */ function enterFunction() { loopSetStack.push(loopsInCurrentScope); loopsInCurrentScope = new Set(); } /** * Reports when the set still contains stored constant conditions * @returns {void} * @private */ function exitFunction() { loopsInCurrentScope = loopSetStack.pop(); } /** * Checks node when checkLoops option is enabled * @param {ASTNode} node The AST node to check. * @returns {void} * @private */ function checkLoop(node) { if (checkLoops === "all" || checkLoops === "allExceptWhileTrue") { trackConstantConditionLoop(node); } } //-------------------------------------------------------------------------- // Public //-------------------------------------------------------------------------- return { ConditionalExpression: reportIfConstant, IfStatement: reportIfConstant, WhileStatement(node) { if ( node.test.type === "Literal" && node.test.value === true && checkLoops === "allExceptWhileTrue" ) { return; } checkLoop(node); }, "WhileStatement:exit": checkConstantConditionLoopInSet, DoWhileStatement: checkLoop, "DoWhileStatement:exit": checkConstantConditionLoopInSet, ForStatement: checkLoop, "ForStatement > .test": node => checkLoop(node.parent), "ForStatement:exit": checkConstantConditionLoopInSet, FunctionDeclaration: enterFunction, "FunctionDeclaration:exit": exitFunction, FunctionExpression: enterFunction, "FunctionExpression:exit": exitFunction, YieldExpression: () => loopsInCurrentScope.clear(), }; }, };