Bug 1773740 - Part 3: Cover js files including ChromeUtils r=Standard8

Differential Revision: https://phabricator.services.mozilla.com/D148938

docs/code-quality/lint/linters/eslint-plugin-mozilla/use-isInstance.rst

@@ -5,6 +5,17 @@ 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.
 
+These files are covered:
+
+- ``*.sys.mjs``
+- ``*.jsm``
+- ``*.jsm.js``
+- ``*.js`` with a heuristic
+
+Since there is no straightforward way to detect chrome scripts, currently the
+linter assumes that any script including ``ChromeUtils`` is chrome privileged.
+This of course may not be sufficient and is open for change.
+
 Examples of incorrect code for this rule:
 -----------------------------------------
 

tools/lint/eslint/eslint-plugin-mozilla/lib/configs/recommended.js

@@ -55,10 +55,6 @@ module.exports = {
         "mozilla/reject-global-this": "error",
         "mozilla/reject-globalThis-modification": "error",
         "mozilla/reject-top-level-await": "error",
-        // Bug 1703953: We don't have a good way to check a file runs in a
-        // privilieged context. Apply this for these files as we know those are
-        // privilieged, and then include more directories elsewhere.
-        "mozilla/use-isInstance": "error",
         // TODO: Bug 1575506 turn `builtinGlobals` on here.
         // We can enable builtinGlobals for jsms due to their scopes.
         "no-redeclare": ["error", { builtinGlobals: false }],
@@ -178,6 +174,7 @@ module.exports = {
     "mozilla/use-chromeutils-import": "error",
     "mozilla/use-default-preference-values": "error",
     "mozilla/use-includes-instead-of-indexOf": "error",
+    "mozilla/use-isInstance": "error",
     "mozilla/use-ownerGlobal": "error",
     "mozilla/use-returnValue": "error",
     "mozilla/use-services": "error",

tools/lint/eslint/eslint-plugin-mozilla/lib/rules/use-isInstance.js

@@ -74,6 +74,24 @@ function pointsToDOMInterface(currentScope, node) {
   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;
+  }
+
+  // Treat scripts using ChromeUtils as chrome scripts, but not SpecialPowers.ChromeUtils
+  const source = context.getSourceCode().text;
+  return !!source.match(/(^|\s)ChromeUtils/);
+}
+
 module.exports = {
   meta: {
     docs: {
@@ -88,6 +106,10 @@ module.exports = {
    * @param {import("eslint").Rule.RuleContext} context
    */
   create(context) {
+    if (!isChromeContext(context)) {
+      return {};
+    }
+
     return {
       BinaryExpression(node) {
         const { operator, right } = node;

tools/lint/eslint/eslint-plugin-mozilla/tests/use-isInstance.js

@@ -34,6 +34,19 @@ const env = { browser: true };
 function mockChromeScript(code) {
   return {
     code,
+    filename: "foo.sys.mjs",
+    env,
+  };
+}
+
+/**
+ * A test case boilerplate simulating content script.
+ * @param {string} code
+ */
+function mockContentScript(code) {
+  return {
+    code,
+    filename: "foo.js",
     env,
   };
 }
@@ -54,6 +67,11 @@ ruleTester.run("use-isInstance", rule, {
     mockChromeScript("var File;file instanceof File;"),
     mockChromeScript("foo instanceof RandomGlobalThing;"),
     mockChromeScript("foo instanceof lazy.RandomGlobalThing;"),
+    mockContentScript("node instanceof Node;"),
+    mockContentScript("file instanceof File;"),
+    mockContentScript(
+      "SpecialPowers.ChromeUtils.import(''); file instanceof File;"
+    ),
   ],
   invalid: [
     {
@@ -61,32 +79,52 @@ ruleTester.run("use-isInstance", rule, {
       output: "Node.isInstance(node)",
       env,
       errors,
+      filename: "foo.sys.mjs",
     },
     {
       code: "text instanceof win.Text",
       output: "win.Text.isInstance(text)",
       errors,
+      filename: "foo.sys.mjs",
     },
     {
       code: "target instanceof this.contentWindow.HTMLAudioElement",
       output: "this.contentWindow.HTMLAudioElement.isInstance(target)",
       errors,
+      filename: "foo.sys.mjs",
     },
     {
       code: "target instanceof File",
       output: "File.isInstance(target)",
       env,
       errors,
+      filename: "foo.sys.mjs",
     },
     {
       code: "target instanceof win.File",
       output: "win.File.isInstance(target)",
       errors,
+      filename: "foo.sys.mjs",
     },
     {
       code: "window.arguments[0] instanceof window.XULElement",
       output: "window.XULElement.isInstance(window.arguments[0])",
       errors,
+      filename: "foo.sys.mjs",
+    },
+    {
+      code: "ChromeUtils.import(''); node instanceof Node",
+      output: "ChromeUtils.import(''); Node.isInstance(node)",
+      env,
+      errors,
+      filename: "foo.js",
+    },
+    {
+      code: "ChromeUtils.import(''); file instanceof File",
+      output: "ChromeUtils.import(''); File.isInstance(file)",
+      env,
+      errors,
+      filename: "foo.js",
     },
   ],
 });