Bug 1620542 - Turn on linting of .eslintrc.js files. r=mossop

Differential Revision: https://phabricator.services.mozilla.com/D65704

--HG--
extra : moz-landing-system : lando

.eslintignore

@@ -7,6 +7,8 @@
 # - intentionally invalid files
 # - build directories and other items that we need to ignore
 
+!.eslintrc.js
+
 # Always ignore node_modules.
 **/node_modules/
 

.eslintrc.js

@@ -59,6 +59,16 @@ module.exports = {
   extends: ["plugin:mozilla/recommended"],
   plugins: ["mozilla"],
   overrides: [
+    {
+      // All .eslintrc.js files are in the node environment, so turn that
+      // on here.
+      // https://github.com/eslint/eslint/issues/13008
+      files: [".eslintrc.js"],
+      env: {
+        node: true,
+        browser: false,
+      },
+    },
     {
       files: [
         "*.html",

browser/components/newtab/content-src/.eslintrc.js

@@ -1,3 +1,5 @@
+/* eslint-disable import/no-commonjs */
+
 module.exports = {
   rules: {
     "import/no-commonjs": 2,

browser/components/newtab/test/.eslintrc.js

@@ -1,3 +1,5 @@
+/* eslint-disable import/no-commonjs */
+
 module.exports = {
   env: {
     mocha: true,

devtools/platform/tests/xpcshell/.eslintrc.js

@@ -1,3 +1,5 @@
+"use strict";
+
 // Parent config file for all devtools xpcshell files.
 module.exports = {
   extends: ["plugin:mozilla/xpcshell-test"],