Enable unicorn/prefer-at unconditionally (PR 15014 follow-up)

Now that Node.js version 18 is required, we should be able to use `Array.prototype.at()` everywhere in the code-base.

external/.eslintrc

@@ -6,8 +6,4 @@
   "env": {
     "node": true,
   },
-
-  "rules": {
-    "unicorn/prefer-at": "off",
-  },
 }

external/builder/builder.js

@@ -72,7 +72,7 @@ function preprocess(inFilename, outFilename, defines) {
       ? outFilename
       : function (line) {
           if (!line || AllWhitespaceRegexp.test(line)) {
-            const prevLine = out[out.length - 1];
+            const prevLine = out.at(-1);
             if (!prevLine || AllWhitespaceRegexp.test(prevLine)) {
               return; // Avoid adding consecutive blank lines.
             }

external/builder/preprocessor2.js

@@ -244,8 +244,8 @@ function postprocessNode(ctx, node) {
       const block = node.body;
       if (
         block.body.length > 0 &&
-        block.body[block.body.length - 1].type === "ReturnStatement" &&
-        !block.body[block.body.length - 1].argument
+        block.body.at(-1).type === "ReturnStatement" &&
+        !block.body.at(-1).argument
       ) {
         // Function body ends with return without arg -- removing it.
         block.body.pop();

external/cmapscompress/compress.js

@@ -215,7 +215,7 @@ function parseCMap(binaryData) {
     },
     readHexSigned(size) {
       const num = this.readHexNumber(size);
-      const sign = fromHexDigit(num[num.length - 1]) & 1 ? 15 : 0;
+      const sign = fromHexDigit(num.at(-1)) & 1 ? 15 : 0;
       let c = 0;
       let result = "";
       for (const digit of num) {

external/cmapscompress/optimize.js

@@ -151,10 +151,7 @@ exports.optimizeCMap = function (data) {
       const maxDistance = 100,
         minItems = 10,
         itemsPerBucket = 50;
-      if (
-        subitems.length > minItems &&
-        codes[codes.length - 1] - codes[0] > maxDistance
-      ) {
+      if (subitems.length > minItems && codes.at(-1) - codes[0] > maxDistance) {
         const gapsCount = Math.max(2, (subitems.length / itemsPerBucket) | 0);
         const gaps = [];
         for (let q = 0; q < gapsCount; q++) {

test/test.js

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable no-var, unicorn/prefer-at */
+/* eslint-disable no-var */
 
 "use strict";
 
@@ -750,9 +750,7 @@ function refTestPostHandler(req, res) {
       });
     }
 
-    var isDone =
-      taskResults[taskResults.length - 1] &&
-      taskResults[taskResults.length - 1][lastPageNum - 1];
+    var isDone = taskResults.at(-1) && taskResults.at(-1)[lastPageNum - 1];
     if (isDone) {
       checkRefTestResults(browser, id, taskResults);
       session.remaining--;