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diff --git a/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/use-isInstance.js b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/use-isInstance.js
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+++ b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/use-isInstance.js
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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") ||
+ filename.endsWith(".jsm.js");
+ 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/use-isInstance.html",
+ },
+ fixable: "code",
+ 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,
+ message:
+ "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.",
+ fix(fixer) {
+ const sourceCode = context.getSourceCode();
+ return fixer.replaceText(
+ node,
+ `${sourceCode.getText(right)}.isInstance(${sourceCode.getText(
+ node.left
+ )})`
+ );
+ },
+ });
+ }
+ },
+ };
+ },
+};