feat: streamlined eslint.config.js with better tseslint.config usage (#…

…1697)

## PR Checklist

- [x] Addresses an existing open issue: fixes #1690
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Applies the changes in the issue. This brings the file line count
-including comments- from 166 to 140.

Removes the `files: ["**/*.md/*.ts"],` from this repo's
`eslint.config.js` because there's no `ts` codeblock in the README.md.

Updates the `typescript-eslint` package by necessity for the
`defaultProject` default.

💖

eslint.config.js

@@ -49,7 +49,7 @@ export default tseslint.config(
 	packageJson,
 	perfectionist.configs["recommended-natural"],
 	regexp.configs["flat/recommended"],
-	...tseslint.config({
+	{
 		extends: [
 			...tseslint.configs.strictTypeChecked,
 			...tseslint.configs.stylisticTypeChecked,
@@ -59,23 +59,13 @@ export default tseslint.config(
 			parserOptions: {
 				projectService: {
 					allowDefaultProject: ["*.config.*s", "bin/*.js", "script/*.ts"],
-					defaultProject: "./tsconfig.json",
 				},
 				tsconfigRootDir: import.meta.dirname,
 			},
 		},
 		rules: {
-			// These off-by-default rules work well for this repo and we like them on.
-			"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/lines-before-block": "off",
-			"no-constant-condition": "off",
 
 			// These on-by-default rules work well for this repo if configured
 			"@typescript-eslint/no-unnecessary-condition": [
@@ -84,7 +74,6 @@ export default tseslint.config(
 					allowConstantLoopConditions: true,
 				},
 			],
-			"@typescript-eslint/no-unused-vars": ["error", { caughtErrors: "all" }],
 			"@typescript-eslint/prefer-nullish-coalescing": [
 				"error",
 				{ ignorePrimitives: true },
@@ -97,47 +86,32 @@ export default tseslint.config(
 				"error",
 				{ allowExperimental: true },
 			],
-			"perfectionist/sort-objects": [
-				"error",
-				{
-					order: "asc",
-					partitionByComment: true,
-					type: "natural",
-				},
-			],
 
 			// Stylistic concerns that don't interfere with Prettier
+			"logical-assignment-operators": [
+				"error",
+				"always",
+				{ enforceForIfStatements: true },
+			],
 			"no-useless-rename": "error",
 			"object-shorthand": "error",
+			"operator-assignment": "error",
 		},
-	}),
-	{
-		files: ["*.jsonc"],
-		rules: {
-			"jsonc/comma-dangle": "off",
-			"jsonc/no-comments": "off",
-			"jsonc/sort-keys": "error",
+		settings: {
+			perfectionist: {
+				partitionByComment: true,
+				type: "natural",
+			},
 		},
 	},
 	{
 		extends: [tseslint.configs.disableTypeChecked],
 		files: ["**/*.md/*.ts"],
-		rules: {
-			"n/no-missing-import": [
-				"error",
-				{ allowModules: ["create-typescript-app"] },
-			],
-		},
 	},
 	{
+		extends: [vitest.configs.recommended],
 		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",

package.json

@@ -100,7 +100,7 @@
 		"tsup": "^8.3.0",
 		"tsx": "^4.17.0",
 		"typescript": "^5.6.2",
-		"typescript-eslint": "^8.1.0",
+		"typescript-eslint": "^8.15.0",
 		"vitest": "^2.1.0"
 	},
 	"engines": {