maint: Upgrade to eslint v9.

Author: thet

.eslintrc.js

@@ -173,7 +173,8 @@ serve: install
 
 upgrade:\
 	.git/hooks/commit-msg\
-	upgrade-remove-husky
+	upgrade-remove-husky\
+	upgrade-eslint
 	@# Upgrade target, depends on other upgrades
 
 
@@ -184,3 +185,17 @@ upgrade-remove-husky:
 		&& git commit -m"maint: @patternslib/dev upgrade - remove .husky directory in favor of git hooks."\
 		|| :
 	-git config --unset core.hooksPath
+
+
+eslint.config.js upgrade-eslint:
+	test -f "eslint.config.js"\
+		|| (\
+			echo 'module.exports = require("@patternslib/dev/eslint.config.js");' > eslint.config.js\
+			&& git add eslint.config.js\
+			&& git commit -m"maint: @patternslib/dev upgrade - create eslint.config.js."\
+		)
+	test -f ".eslintrc.js"\
+		&& rm .eslintrc.js\
+		&& git add .eslintrc.js\
+		&& git commit -m"maint: @patternslib/dev upgrade - remove old .eslintrc.js."\
+		|| :

Makefile

@@ -0,0 +1,37 @@
+const js = require("@eslint/js");
+const config_prettier = require("eslint-config-prettier");
+const globals = require("globals");
+const babel_parser = require("@babel/eslint-parser");
+
+module.exports = [
+    js.configs.recommended,
+    config_prettier,
+    {
+        languageOptions: {
+            ecmaVersion: 2022,
+            globals: {
+                ...globals.browser,
+                ...globals.node,
+                ...globals.jest,
+            },
+            parser: babel_parser,
+        },
+        ignores: [
+            "cache/",
+            "coverage/",
+            "dist/",
+            "node_modules/",
+            "stats.json",
+            "style/",
+        ],
+        rules: {
+            "no-debugger": 1,
+            "no-duplicate-imports": 1,
+            // Do keep due avoid unintendet consequences.
+            "no-alert": 0,
+            "no-control-regex": 0,
+            "no-self-assign": 0,
+            "no-useless-escape": 0,
+        },
+    }
+];

eslint.config.js

@@ -12,8 +12,9 @@
         "@release-it/conventional-changelog": "^10.0.0",
         "babel-loader": "^9.2.1",
         "css-loader": "^7.1.2",
-        "eslint": "^8.57.0",
-        "eslint-config-prettier": "^9.1.0",
+        "eslint": "^9.20.1",
+        "eslint-config-prettier": "^10.0.1",
+        "globals": "^15.15.0",
         "identity-obj-proxy": "^3.0.0",
         "jest": "^29.7.0",
         "jest-environment-jsdom": "^29.7.0",