feat: use ESLint Flat Config

.vscode/settings.json

@@ -14,5 +14,6 @@
 		"yaml"
 	],
 	"eslint.rules.customizations": [{ "rule": "*", "severity": "warn" }],
+	"eslint.useFlatConfig": true,
 	"typescript.tsdk": "node_modules/typescript/lib"
 }

cspell.json

@@ -27,6 +27,7 @@
 		"precommit",
 		"quickstart",
 		"tada",
+		"tseslint",
 		"tsup",
 		"vitest"
 	]

eslint.config.js

@@ -0,0 +1,168 @@
+/*
+👋 Hi! This ESLint configuration contains a lot more stuff than many repos'!
+You can read from it to see all sorts of linting goodness, but don't worry -
+it's not something you need to exhaustively understand immediately. 💙
+
+If you're interested in learning more, see the 'getting started' docs on:
+- ESLint: https://eslint.org
+- typescript-eslint: https://typescript-eslint.io
+*/
+
+import eslint from "@eslint/js";
+import comments from "@eslint-community/eslint-plugin-eslint-comments/configs";
+import deprecation from "eslint-plugin-deprecation";
+import jsdoc from "eslint-plugin-jsdoc";
+import jsonc from "eslint-plugin-jsonc";
+import markdown from "eslint-plugin-markdown";
+import n from "eslint-plugin-n";
+import packageJson from "eslint-plugin-package-json/configs/recommended";
+import perfectionistNatural from "eslint-plugin-perfectionist/configs/recommended-natural";
+import * as regexp from "eslint-plugin-regexp";
+import vitest from "eslint-plugin-vitest";
+import yml from "eslint-plugin-yml";
+import tseslint from "typescript-eslint";
+
+export default tseslint.config(
+	{
+		ignores: [
+			"coverage*",
+			"lib",
+			"node_modules",
+			"pnpm-lock.yaml",
+			"**/*.snap",
+		],
+	},
+	{
+		linterOptions: {
+			reportUnusedDisableDirectives: "error",
+		},
+	},
+	eslint.configs.recommended,
+	...jsonc.configs["flat/recommended-with-json"],
+	...markdown.configs.recommended,
+	...yml.configs["flat/recommended"],
+	...yml.configs["flat/prettier"],
+	comments.recommended,
+	jsdoc.configs["flat/recommended-typescript-error"],
+	n.configs["flat/recommended"],
+	packageJson,
+	perfectionistNatural,
+	regexp.configs["flat/recommended"],
+	...tseslint.config({
+		extends: [
+			...tseslint.configs.strictTypeChecked,
+			...tseslint.configs.stylisticTypeChecked,
+		],
+		files: ["**/*.js", "**/*.ts"],
+		languageOptions: {
+			parserOptions: {
+				EXPERIMENTAL_useProjectService: {
+					allowDefaultProjectForFiles: ["./*.*s", "eslint.config.js"],
+					defaultProject: "./tsconfig.json",
+				},
+			},
+		},
+		plugins: { deprecation },
+		rules: {
+			// These off-by-default rules work well for this repo and we like them on.
+			"deprecation/deprecation": "error",
+			"jsdoc/informative-docs": "error",
+			"logical-assignment-operators": [
+				"error",
+				"always",
+				{ enforceForIfStatements: true },
+			],
+			"operator-assignment": "error",
+
+			// These on-by-default rules don't work well for this repo and we like them off.
+			"jsdoc/require-jsdoc": "off",
+			"jsdoc/require-param": "off",
+			"jsdoc/require-property": "off",
+			"jsdoc/require-returns": "off",
+			"no-constant-condition": "off",
+
+			// These on-by-default rules work well for this repo if configured
+			"@typescript-eslint/no-unnecessary-condition": [
+				"error",
+				{
+					allowConstantLoopConditions: true,
+				},
+			],
+			"@typescript-eslint/no-unused-vars": ["error", { caughtErrors: "all" }],
+			"@typescript-eslint/prefer-nullish-coalescing": [
+				"error",
+				{ ignorePrimitives: true },
+			],
+			"@typescript-eslint/restrict-template-expressions": [
+				"error",
+				{ allowBoolean: true, allowNullish: true, allowNumber: true },
+			],
+			"perfectionist/sort-objects": [
+				"error",
+				{
+					order: "asc",
+					"partition-by-comment": true,
+					type: "natural",
+				},
+			],
+
+			// Stylistic concerns that don't interfere with Prettier
+			"no-useless-rename": "error",
+			"object-shorthand": "error",
+		},
+	}),
+	{
+		files: ["*.jsonc"],
+		rules: {
+			"jsonc/comma-dangle": "off",
+			"jsonc/no-comments": "off",
+			"jsonc/sort-keys": "error",
+		},
+	},
+	{
+		files: ["**/*.md/*.ts"],
+		rules: {
+			// https://github.com/gund/eslint-plugin-deprecation/pull/86
+			"deprecation/deprecation": "off",
+
+			"n/no-missing-import": [
+				"error",
+				{ allowModules: ["create-typescript-app"] },
+			],
+		},
+	},
+	{
+		files: ["**/*.test.*"],
+		languageOptions: {
+			globals: vitest.environments.env.globals,
+		},
+		plugins: { vitest },
+		rules: {
+			...vitest.configs.recommended.rules,
+
+			// These on-by-default rules aren't useful in test files.
+			"@typescript-eslint/no-unsafe-assignment": "off",
+			"@typescript-eslint/no-unsafe-call": "off",
+		},
+	},
+	{
+		files: ["**/*.{yml,yaml}"],
+		rules: {
+			"yml/file-extension": ["error", { extension: "yml" }],
+			"yml/sort-keys": [
+				"error",
+				{
+					order: { type: "asc" },
+					pathPattern: "^.*$",
+				},
+			],
+			"yml/sort-sequence-values": [
+				"error",
+				{
+					order: { type: "asc" },
+					pathPattern: "^.*$",
+				},
+			],
+		},
+	},
+);