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/**
* @fileoverview A rule to disallow `this` keywords outside of classes or class-like objects.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow `this` keywords outside of classes or class-like objects",
category: "Best Practices",
recommended: false,
url: "https://eslint.org/docs/rules/no-invalid-this"
},
schema: []
},
create(context) {
const stack = [],
sourceCode = context.getSourceCode();
/**
* Gets the current checking context.
*
* The return value has a flag that whether or not `this` keyword is valid.
* The flag is initialized when got at the first time.
* @returns {{valid: boolean}}
* an object which has a flag that whether or not `this` keyword is valid.
*/
stack.getCurrent = function() {
const current = this[this.length - 1];
if (!current.init) {
current.init = true;
current.valid = !astUtils.isDefaultThisBinding(
current.node,
sourceCode
);
}
return current;
};
/**
* Pushs new checking context into the stack.
*
* The checking context is not initialized yet.
* Because most functions don't have `this` keyword.
* When `this` keyword was found, the checking context is initialized.
* @param {ASTNode} node A function node that was entered.
* @returns {void}
*/
function enterFunction(node) {
// `this` can be invalid only under strict mode.
stack.push({
init: !context.getScope().isStrict,
node,
valid: true
});
}
/**
* Pops the current checking context from the stack.
* @returns {void}
*/
function exitFunction() {
stack.pop();
}
return {
/*
* `this` is invalid only under strict mode.
* Modules is always strict mode.
*/
Program(node) {
const scope = context.getScope(),
features = context.parserOptions.ecmaFeatures || {};
stack.push({
init: true,
node,
valid: !(
scope.isStrict ||
node.sourceType === "module" ||
(features.globalReturn && scope.childScopes[0].isStrict)
)
});
},
"Program:exit"() {
stack.pop();
},
FunctionDeclaration: enterFunction,
"FunctionDeclaration:exit": exitFunction,
FunctionExpression: enterFunction,
"FunctionExpression:exit": exitFunction,
// Reports if `this` of the current context is invalid.
ThisExpression(node) {
const current = stack.getCurrent();
if (current && !current.valid) {
context.report({ node, message: "Unexpected 'this'." });
}
}
};
}
};
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