VIA-579 AJ Add supported browsers list to warn when using old apis

Author: ankur-jain-nhs

.prettierignore

@@ -4,7 +4,6 @@
 /public/*
 /scripts/*
 /**/*.md
-/**/*.mjs
 project.code-workspace
 /**/.terraform/*
 /package-lock.json

esbuild.config.mjs

@@ -14,10 +14,14 @@ const copyExtraFiles = async () => {
   // there is an issue with esbuild putting a warning for xhr-sync-worker.js file being external
   // at runtime, lambda complains that the file is not present
   // DOMPurify apparently depends on this file
-  fs.copyFile("./node_modules/jsdom/lib/jsdom/living/xhr/xhr-sync-worker.js", `${OUTPUT_DIR}/xhr-sync-worker.js`, (err) => {
-    if (err) throw err;
-    console.log("Copied xhr-sync-worker.js (workaround)");
-  });
+  fs.copyFile(
+    "./node_modules/jsdom/lib/jsdom/living/xhr/xhr-sync-worker.js",
+    `${OUTPUT_DIR}/xhr-sync-worker.js`,
+    (err) => {
+      if (err) throw err;
+      console.log("Copied xhr-sync-worker.js (workaround)");
+    },
+  );
 };
 
 const buildLambda = async () => {
@@ -29,7 +33,7 @@ const buildLambda = async () => {
     jsx: "automatic",
     target: "node22",
     external: ["./xhr-sync-worker.js"],
-    outfile: `${OUTPUT_DIR}/lambda.js`
+    outfile: `${OUTPUT_DIR}/lambda.js`,
   });
 };
 

eslint.config.mjs

@@ -1,6 +1,7 @@
+import { FlatCompat } from "@eslint/eslintrc";
+import compat_plugin from "eslint-plugin-compat";
 import { dirname } from "path";
 import { fileURLToPath } from "url";
-import { FlatCompat } from "@eslint/eslintrc";
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = dirname(__filename);
@@ -9,32 +10,45 @@ const compat = new FlatCompat({
   baseDirectory: __dirname,
 });
 
-const eslintConfig = [{
-  ignores: [
-    "node_modules/**",
-    ".next/**",
-    "out/**",
-    "build/**",
-    "next-env.d.ts",
-    "public/**",
-    "dist/**",
-    "docs/**",
-    "coverage/**",
-    "**/.terraform/**",
-    ".open-next/**",
-    "playwright-report/**",
-    "pact/**",
-    "performance/report",
-  ]
-}, ...compat.extends(
-  "next/core-web-vitals",
-  "next/typescript",
-  "prettier",
-  "next",
-), {
-  "rules": {
-    "@typescript-eslint/no-unused-vars": "error",
-  }
-}];
+const eslintConfig = [
+  {
+    ignores: [
+      "node_modules/**",
+      ".next/**",
+      "out/**",
+      "build/**",
+      "next-env.d.ts",
+      "public/**",
+      "dist/**",
+      "docs/**",
+      "coverage/**",
+      "**/.terraform/**",
+      ".open-next/**",
+      "playwright-report/**",
+      "pact/**",
+      "performance/report",
+    ],
+  },
+  ...compat.extends("next/core-web-vitals", "next/typescript", "prettier", "next"),
+  compat_plugin.configs["flat/recommended"],
+  {
+    rules: {
+      "@typescript-eslint/no-unused-vars": "error",
+
+      // nhsuk-frontend: https://github.com/nhsuk/nhsuk-frontend/blob/main/docs/contributing/browser-support.md
+      // Ref: https://github.com/nhsuk/nhsuk-frontend/blob/main/packages/nhsuk-frontend/.browserslistrc
+      // supported browsers are listed in package.json
+      "compat/compat": "warn",
+    },
+  },
+
+  // Override for test files: turn off compat
+  {
+    files: ["**/*.test.{js,jsx,ts,tsx}", "**/*.spec.{js,jsx,ts,tsx}", "test-data/**"],
+    rules: {
+      "compat/compat": "off",
+    },
+  },
+];
 
 export default eslintConfig;

package-lock.json

@@ -8,6 +8,17 @@
     "doc": "docs",
     "test": "tests"
   },
+  "browserslist": [
+    "> 0.1% in GB and not dead",
+    "last 6 Chrome versions",
+    "last 6 Firefox versions",
+    "last 6 Edge versions",
+    "last 2 Samsung versions",
+    "Firefox ESR",
+    "Safari >= 11",
+    "iOS >= 11",
+    "IE 11"
+  ],
   "scripts": {
     "dev": "next dev --turbopack --experimental-https",
     "app": "npm run build && npm run start",
@@ -56,10 +67,12 @@
     "@types/node": "^24.10.1",
     "@types/react": "^19.2.7",
     "@types/react-dom": "^19.2.3",
+    "es-check": "^9.5.2",
     "esbuild": "0.27.1",
     "eslint": "^9.39.1",
     "eslint-config-next": "15.5.7",
     "eslint-config-prettier": "^10.1.8",
+    "eslint-plugin-compat": "^6.0.2",
     "jest": "^30.2.0",
     "jest-environment-jsdom": "^30.2.0",
     "jest-pact": "^0.13.0",