tools: enable ESLint no-sparse-arrays rule

PR-URL: #41463
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>

.eslintrc.js

@@ -275,6 +275,7 @@ module.exports = {
     'no-self-compare': 'error',
     'no-setter-return': 'error',
     'no-shadow-restricted-names': 'error',
+    'no-sparse-arrays': 'error',
     'no-tabs': 'error',
     'no-template-curly-in-string': 'error',
     'no-this-before-super': 'error',

lib/internal/modules/esm/get_format.js

@@ -45,7 +45,7 @@ const protocolHandlers = ObjectAssign(ObjectCreate(null), {
     const { 1: mime } = RegExpPrototypeExec(
       /^([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
       parsed.pathname,
-    ) || [, null];
+    ) || [, null]; // eslint-disable-line no-sparse-arrays
     const format = ({
       '__proto__': null,
       'text/javascript': 'module',

test/parallel/test-assert-deep.js

@@ -567,8 +567,10 @@ assertNotDeepOrStrict(
 
 // Handle sparse arrays.
 {
+  /* eslint-disable no-sparse-arrays */
   assertDeepAndStrictEqual([1, , , 3], [1, , , 3]);
   assertNotDeepOrStrict([1, , , 3], [1, , , 3, , , ]);
+  /* eslint-enable no-sparse-arrays */
   const a = new Array(3);
   const b = new Array(3);
   a[2] = true;

test/parallel/test-util-inspect.js

@@ -434,7 +434,7 @@ assert.strictEqual(
 
 // Array with extra properties.
 {
-  const arr = [1, 2, 3, , ];
+  const arr = [1, 2, 3, , ]; // eslint-disable-line no-sparse-arrays
   arr.foo = 'bar';
   assert.strictEqual(util.inspect(arr),
                      "[ 1, 2, 3, <1 empty item>, foo: 'bar' ]");
@@ -2142,6 +2142,7 @@ assert.strictEqual(util.inspect('"\'${a}'), "'\"\\'${a}'");
   [function() {}, '[Function (anonymous)]'],
   [() => {}, '[Function (anonymous)]'],
   [[1, 2], '[ 1, 2 ]'],
+  // eslint-disable-next-line no-sparse-arrays
   [[, , 5, , , , ], '[ <2 empty items>, 5, <3 empty items> ]'],
   [{ a: 5 }, '{ a: 5 }'],
   [new Set([1, 2]), 'Set(2) { 1, 2 }'],

test/parallel/test-util-isDeepStrictEqual.js

@@ -409,8 +409,10 @@ notUtilIsDeepStrict(
 }
 
 // Handle sparse arrays
+/* eslint-disable no-sparse-arrays */
 utilIsDeepStrict([1, , , 3], [1, , , 3]);
 notUtilIsDeepStrict([1, , , 3], [1, , , 3, , , ]);
+/* eslint-enable no-sparse-arrays */
 
 // Handle different error messages
 {