From ceffff389336db34cf293700159cba0ddad360df Mon Sep 17 00:00:00 2001
From: Stephen Wade <stephen@stephenwade.me>
Date: Sat, 22 May 2021 16:04:40 -0400
Subject: [PATCH] Chore: Replace old syntax for Array flat/flatMap

---
 lib/linter/apply-disable-directives.js | 16 +---------------
 lib/linter/linter.js                   |  3 +--
 lib/linter/node-event-generator.js     |  4 +---
 lib/rules/max-lines.js                 | 16 +---------------
 4 files changed, 4 insertions(+), 35 deletions(-)

diff --git a/lib/linter/apply-disable-directives.js b/lib/linter/apply-disable-directives.js
index 0ba69ca9cc44..ad250a9e52c4 100644
--- a/lib/linter/apply-disable-directives.js
+++ b/lib/linter/apply-disable-directives.js
@@ -122,21 +122,7 @@ module.exports = ({ directives, problems, reportUnusedDisableDirectives = "off"
         .map(directive => Object.assign({}, directive, { unprocessedDirective: directive }))
         .sort(compareLocations);
 
-    /**
-     * Returns a new array formed by applying a given callback function to each element of the array, and then flattening the result by one level.
-     * TODO(stephenwade): Replace this with array.flatMap when we drop support for Node v10
-     * @param {any[]} array The array to process
-     * @param {Function} fn The function to use
-     * @returns {any[]} The result array
-     */
-    function flatMap(array, fn) {
-        const mapped = array.map(fn);
-        const flattened = [].concat(...mapped);
-
-        return flattened;
-    }
-
-    const lineDirectives = flatMap(directives, directive => {
+    const lineDirectives = directives.flatMap(directive => {
         switch (directive.type) {
             case "disable":
             case "enable":
diff --git a/lib/linter/linter.js b/lib/linter/linter.js
index bdc6c1b1d016..86829787197b 100644
--- a/lib/linter/linter.js
+++ b/lib/linter/linter.js
@@ -1287,8 +1287,7 @@ class Linter {
         const text = ensureText(textOrSourceCode);
         const preprocess = options.preprocess || (rawText => [rawText]);
 
-        // TODO(stephenwade): Replace this with array.flat() when we drop support for Node v10
-        const postprocess = options.postprocess || (array => [].concat(...array));
+        const postprocess = options.postprocess || Array.prototype.flat.call;
         const filterCodeBlock =
             options.filterCodeBlock ||
             (blockFilename => blockFilename.endsWith(".js"));
diff --git a/lib/linter/node-event-generator.js b/lib/linter/node-event-generator.js
index 8b619fdff83e..9b058247b3e6 100644
--- a/lib/linter/node-event-generator.js
+++ b/lib/linter/node-event-generator.js
@@ -37,9 +37,7 @@ const esquery = require("esquery");
  * @returns {any[]} The union of the input arrays
  */
 function union(...arrays) {
-
-    // TODO(stephenwade): Replace this with arrays.flat() when we drop support for Node v10
-    return [...new Set([].concat(...arrays))];
+    return [...new Set(arrays.flat())];
 }
 
 /**
diff --git a/lib/rules/max-lines.js b/lib/rules/max-lines.js
index 8bd5a1c95f40..0837dd1f0fde 100644
--- a/lib/rules/max-lines.js
+++ b/lib/rules/max-lines.js
@@ -137,20 +137,6 @@ module.exports = {
             return [];
         }
 
-        /**
-         * Returns a new array formed by applying a given callback function to each element of the array, and then flattening the result by one level.
-         * TODO(stephenwade): Replace this with array.flatMap when we drop support for Node v10
-         * @param {any[]} array The array to process
-         * @param {Function} fn The function to use
-         * @returns {any[]} The result array
-         */
-        function flatMap(array, fn) {
-            const mapped = array.map(fn);
-            const flattened = [].concat(...mapped);
-
-            return flattened;
-        }
-
         return {
             "Program:exit"() {
                 let lines = sourceCode.lines.map((text, i) => ({
@@ -173,7 +159,7 @@ module.exports = {
                 if (skipComments) {
                     const comments = sourceCode.getAllComments();
 
-                    const commentLines = flatMap(comments, comment => getLinesWithoutCode(comment));
+                    const commentLines = comments.flatMap(getLinesWithoutCode);
 
                     lines = lines.filter(
                         l => !commentLines.includes(l.lineNumber)