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150 lines
5.0 KiB
150 lines
5.0 KiB
/**
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* @fileoverview A rule to disallow `this` keywords in contexts where the value of `this` is `undefined`.
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* @author Toru Nagashima
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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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/**
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* Determines if the given code path is a code path with lexical `this` binding.
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* That is, if `this` within the code path refers to `this` of surrounding code path.
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* @param {CodePath} codePath Code path.
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* @param {ASTNode} node Node that started the code path.
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* @returns {boolean} `true` if it is a code path with lexical `this` binding.
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*/
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function isCodePathWithLexicalThis(codePath, node) {
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return codePath.origin === "function" && node.type === "ArrowFunctionExpression";
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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: "suggestion",
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docs: {
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description: "Disallow use of `this` in contexts where the value of `this` is `undefined`",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/no-invalid-this"
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},
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schema: [
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{
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type: "object",
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properties: {
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capIsConstructor: {
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type: "boolean",
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default: true
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}
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},
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additionalProperties: false
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}
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],
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messages: {
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unexpectedThis: "Unexpected 'this'."
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}
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},
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create(context) {
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const options = context.options[0] || {};
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const capIsConstructor = options.capIsConstructor !== false;
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const stack = [],
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sourceCode = context.sourceCode;
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/**
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* Gets the current checking context.
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*
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* The return value has a flag that whether or not `this` keyword is valid.
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* The flag is initialized when got at the first time.
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* @returns {{valid: boolean}}
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* an object which has a flag that whether or not `this` keyword is valid.
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*/
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stack.getCurrent = function() {
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const current = this[this.length - 1];
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if (!current.init) {
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current.init = true;
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current.valid = !astUtils.isDefaultThisBinding(
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current.node,
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sourceCode,
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{ capIsConstructor }
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);
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}
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return current;
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};
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return {
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onCodePathStart(codePath, node) {
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if (isCodePathWithLexicalThis(codePath, node)) {
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return;
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}
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if (codePath.origin === "program") {
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const scope = sourceCode.getScope(node);
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const features = context.languageOptions.parserOptions.ecmaFeatures || {};
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// `this` at the top level of scripts always refers to the global object
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stack.push({
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init: true,
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node,
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valid: !(
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node.sourceType === "module" ||
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(features.globalReturn && scope.childScopes[0].isStrict)
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)
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});
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return;
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}
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/*
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* `init: false` means that `valid` isn't determined yet.
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* Most functions don't use `this`, and the calculation for `valid`
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* is relatively costly, so we'll calculate it lazily when the first
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* `this` within the function is traversed. A special case are non-strict
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* functions, because `this` refers to the global object and therefore is
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* always valid, so we can set `init: true` right away.
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*/
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stack.push({
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init: !sourceCode.getScope(node).isStrict,
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node,
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valid: true
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});
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},
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onCodePathEnd(codePath, node) {
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if (isCodePathWithLexicalThis(codePath, node)) {
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return;
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}
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stack.pop();
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},
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// Reports if `this` of the current context is invalid.
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ThisExpression(node) {
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const current = stack.getCurrent();
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if (current && !current.valid) {
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context.report({
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node,
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messageId: "unexpectedThis"
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});
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}
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}
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};
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}
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};
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