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/**
* @fileoverview Rule to flag the generator functions that does not have yield.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../types').Rule.RuleModule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "Require generator functions to contain `yield`",
recommended: true,
url: "https://eslint.org/docs/latest/rules/require-yield",
},
schema: [],
messages: {
missingYield: "This generator function does not have 'yield'.",
},
},
create(context) {
const stack = [];
/**
* If the node is a generator function, start counting `yield` keywords.
* @param {Node} node A function node to check.
* @returns {void}
*/
function beginChecking(node) {
if (node.generator) {
stack.push(0);
}
}
/**
* If the node is a generator function, end counting `yield` keywords, then
* reports result.
* @param {Node} node A function node to check.
* @returns {void}
*/
function endChecking(node) {
if (!node.generator) {
return;
}
const countYield = stack.pop();
if (countYield === 0 && node.body.body.length > 0) {
context.report({ node, messageId: "missingYield" });
}
}
return {
FunctionDeclaration: beginChecking,
"FunctionDeclaration:exit": endChecking,
FunctionExpression: beginChecking,
"FunctionExpression:exit": endChecking,
// Increases the count of `yield` keyword.
YieldExpression() {
if (stack.length > 0) {
stack[stack.length - 1] += 1;
}
},
};
},
};
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