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/**
* @fileoverview Reject use of instanceof against DOM interfaces
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
"use strict";
const fs = require("fs");
const { maybeGetMemberPropertyName } = require("../helpers");
const privilegedGlobals = Object.keys(
require("../environments/privileged.js").globals
);
// -----------------------------------------------------------------------------
// Rule Definition
// -----------------------------------------------------------------------------
/**
* Whether an identifier is defined by eslint configuration.
* `env: { browser: true }` or `globals: []` for example.
* @param {import("eslint-scope").Scope} currentScope
* @param {import("estree").Identifier} id
*/
function refersToEnvironmentGlobals(currentScope, id) {
const reference = currentScope.references.find(ref => ref.identifier === id);
const { resolved } = reference || {};
if (!resolved) {
return false;
}
// No definition in script files; defined via .eslintrc
return resolved.scope.type === "global" && resolved.defs.length === 0;
}
/**
* Whether a node points to a DOM interface.
* Includes direct references to interfaces objects and also indirect references
* via property access.
* OS.File and lazy.(Foo) are explicitly excluded.
*
* @example HTMLElement
* @example win.HTMLElement
* @example iframe.contentWindow.HTMLElement
* @example foo.HTMLElement
*
* @param {import("eslint-scope").Scope} currentScope
* @param {import("estree").Node} node
*/
function pointsToDOMInterface(currentScope, node) {
if (node.type === "MemberExpression") {
const objectName = maybeGetMemberPropertyName(node.object);
if (objectName === "lazy") {
// lazy.Foo is probably a non-IDL import.
return false;
}
if (objectName === "OS" && node.property.name === "File") {
// OS.File is an exception that is not a Web IDL interface
return false;
}
// For `win.Foo`, `iframe.contentWindow.Foo`, or such.
return privilegedGlobals.includes(node.property.name);
}
if (
node.type === "Identifier" &&
refersToEnvironmentGlobals(currentScope, node)
) {
return privilegedGlobals.includes(node.name);
}
return false;
}
/**
* @param {import("eslint").Rule.RuleContext} context
*/
function isChromeContext(context) {
const filename = context.getFilename();
const isChromeFileName =
filename.endsWith(".sys.mjs") || filename.endsWith(".jsm");
if (isChromeFileName) {
return true;
}
if (filename.endsWith(".xhtml")) {
// Treat scripts in XUL files as chrome scripts
// Note: readFile is needed as getSourceCode() only gives JS blocks
return fs.readFileSync(filename).includes("there.is.only.xul");
}
// Treat scripts as chrome privileged when using:
// 1. ChromeUtils, but not SpecialPowers.ChromeUtils
// 2. BrowserTestUtils, PlacesUtils
// 3. document.createXULElement
// 4. loader.lazyRequireGetter
// 5. Services.foo, but not SpecialPowers.Services.foo
// 6. evalInSandbox
const source = context.getSourceCode().text;
return !!source.match(
/(^|\s)ChromeUtils|BrowserTestUtils|PlacesUtils|createXULElement|lazyRequireGetter|(^|\s)Services\.|evalInSandbox/
);
}
module.exports = {
meta: {
docs: {
url: "https://firefox-source-docs.mozilla.org/code-quality/lint/linters/eslint-plugin-mozilla/rules/use-isInstance.html",
},
fixable: "code",
messages: {
preferIsInstance:
"Please prefer .isInstance() in chrome scripts over the standard instanceof operator for DOM interfaces, " +
"since the latter will return false when the object is created from a different context.",
},
schema: [],
type: "problem",
},
/**
* @param {import("eslint").Rule.RuleContext} context
*/
create(context) {
if (!isChromeContext(context)) {
return {};
}
return {
BinaryExpression(node) {
const { operator, right } = node;
if (
operator === "instanceof" &&
pointsToDOMInterface(context.getScope(), right)
) {
context.report({
node,
messageId: "preferIsInstance",
fix(fixer) {
const sourceCode = context.getSourceCode();
return fixer.replaceText(
node,
`${sourceCode.getText(right)}.isInstance(${sourceCode.getText(
node.left
)})`
);
},
});
}
},
};
},
};
|
