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/**
* @fileoverview Rule to flag use constant conditions
* @author Christian Schulz <http://rndm.de>
*/
"use strict";
const { isConstant } = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "problem",
docs: {
description: "disallow constant expressions in conditions",
recommended: true,
url: "https://eslint.org/docs/rules/no-constant-condition"
},
schema: [
{
type: "object",
properties: {
checkLoops: {
type: "boolean",
default: true
}
},
additionalProperties: false
}
],
messages: {
unexpected: "Unexpected constant condition."
}
},
create(context) {
const options = context.options[0] || {},
checkLoops = options.checkLoops !== false,
loopSetStack = [];
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(context.getScope(), 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(context.getScope(), 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) {
trackConstantConditionLoop(node);
}
}
//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------
return {
ConditionalExpression: reportIfConstant,
IfStatement: reportIfConstant,
WhileStatement: checkLoop,
"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()
};
}
};
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