/**
* @fileoverview Rule to flag use of eval() statement
* @author Nicholas C. Zakas
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("../ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const candidatesOfGlobalObject = Object.freeze([
"global",
"window"
]);
/**
* Checks a given node is a Identifier node of the specified name.
*
* @param {ASTNode} node - A node to check.
* @param {string} name - A name to check.
* @returns {boolean} `true` if the node is a Identifier node of the name.
*/
function isIdentifier(node, name) {
return node.type === "Identifier" && node.name === name;
}
/**
* Checks a given node is a Literal node of the specified string value.
*
* @param {ASTNode} node - A node to check.
* @param {string} name - A name to check.
* @returns {boolean} `true` if the node is a Literal node of the name.
*/
function isConstant(node, name) {
switch (node.type) {
case "Literal":
return node.value === name;
case "TemplateLiteral":
return (
node.expressions.length === 0 &&
node.quasis[0].value.cooked === name
);
default:
return false;
}
}
/**
* Checks a given node is a MemberExpression node which has the specified name's
* property.
*
* @param {ASTNode} node - A node to check.
* @param {string} name - A name to check.
* @returns {boolean} `true` if the node is a MemberExpression node which has
* the specified name's property
*/
function isMember(node, name) {
return (
node.type === "MemberExpression" &&
(node.computed ? isConstant : isIdentifier)(node.property, name)
);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "disallow the use of `eval()`",
category: "Best Practices",
recommended: false,
url: "https://eslint.org/docs/rules/no-eval"
},
schema: [
{
type: "object",
properties: {
allowIndirect: { type: "boolean" }
},
additionalProperties: false
}
]
},
create(context) {
const allowIndirect = Boolean(
context.options[0] &&
context.options[0].allowIndirect
);
const sourceCode = context.getSourceCode();
let funcInfo = null;
/**
* Pushs a variable scope (Program or Function) information to the stack.
*
* This is used in order to check whether or not `this` binding is a
* reference to the global object.
*
* @param {ASTNode} node - A node of the scope. This is one of Program,
* FunctionDeclaration, FunctionExpression, and ArrowFunctionExpression.
* @returns {void}
*/
function enterVarScope(node) {
const strict = context.getScope().isStrict;
funcInfo = {
upper: funcInfo,
node,
strict,
defaultThis: false,
initialized: strict
};
}
/**
* Pops a variable scope from the stack.
*
* @returns {void}
*/
function exitVarScope() {
funcInfo = funcInfo.upper;
}
/**
* Reports a given node.
*
* `node` is `Identifier` or `MemberExpression`.
* The parent of `node` might be `CallExpression`.
*
* The location of the report is always `eval` `Identifier` (or possibly
* `Literal`). The type of the report is `CallExpression` if the parent is
* `CallExpression`. Otherwise, it's the given node type.
*
* @param {ASTNode} node - A node to report.
* @returns {void}
*/
function report(node) {
let locationNode = node;
const parent = node.parent;
if (node.type === "MemberExpression") {
locationNode = node.property;
}
if (parent.type === "CallExpression" && parent.callee === node) {
node = parent;
}
context.report({
node,
loc: locationNode.loc.start,
message: "eval can be harmful."
});
}
/**
* Reports accesses of `eval` via the global object.
*
* @param {eslint-scope.Scope} globalScope - The global scope.
* @returns {void}
*/
function reportAccessingEvalViaGlobalObject(globalScope) {
for (let i = 0; i < candidatesOfGlobalObject.length; ++i) {
const name = candidatesOfGlobalObject[i];
const variable = astUtils.getVariableByName(globalScope, name);
if (!variable) {
continue;
}
const references = variable.references;
for (let j = 0; j < references.length; ++j) {
const identifier = references[j].identifier;
let node = identifier.parent;
// To detect code like `window.window.eval`.
while (isMember(node, name)) {
node = node.parent;
}
// Reports.
if (isMember(node, "eval")) {
report(node);
}
}
}
}
/**
* Reports all accesses of `eval` (excludes direct calls to eval).
*
* @param {eslint-scope.Scope} globalScope - The global scope.
* @returns {void}
*/
function reportAccessingEval(globalScope) {
const variable = astUtils.getVariableByName(globalScope, "eval");
if (!variable) {
return;
}
const references = variable.references;
for (let i = 0; i < references.length; ++i) {
const reference = references[i];
const id = reference.identifier;
if (id.name === "eval" && !astUtils.isCallee(id)) {
// Is accessing to eval (excludes direct calls to eval)
report(id);
}
}
}
if (allowIndirect) {
// Checks only direct calls to eval. It's simple!
return {
"CallExpression:exit"(node) {
const callee = node.callee;
if (isIdentifier(callee, "eval")) {
report(callee);
}
}
};
}
return {
"CallExpression:exit"(node) {
const callee = node.callee;
if (isIdentifier(callee, "eval")) {
report(callee);
}
},
Program(node) {
const scope = context.getScope(),
features = context.parserOptions.ecmaFeatures || {},
strict =
scope.isStrict ||
node.sourceType === "module" ||
(features.globalReturn && scope.childScopes[0].isStrict);
funcInfo = {
upper: null,
node,
strict,
defaultThis: true,
initialized: true
};
},
"Program:exit"() {
const globalScope = context.getScope();
exitVarScope();
reportAccessingEval(globalScope);
reportAccessingEvalViaGlobalObject(globalScope);
},
FunctionDeclaration: enterVarScope,
"FunctionDeclaration:exit": exitVarScope,
FunctionExpression: enterVarScope,
"FunctionExpression:exit": exitVarScope,
ArrowFunctionExpression: enterVarScope,
"ArrowFunctionExpression:exit": exitVarScope,
ThisExpression(node) {
if (!isMember(node.parent, "eval")) {
return;
}
/*
* `this.eval` is found.
* Checks whether or not the value of `this` is the global object.
*/
if (!funcInfo.initialized) {
funcInfo.initialized = true;
funcInfo.defaultThis = astUtils.isDefaultThisBinding(
funcInfo.node,
sourceCode
);
}
if (!funcInfo.strict && funcInfo.defaultThis) {
// `this.eval` is possible built-in `eval`.
report(node.parent);
}
}
};
}
};