chore: enable typescript-eslint's recommended and stylistic configs i…

…nternally (#52948)

Spinning out from #37151 and my draft PR #52845, this enables the two
basic recommended rulesets from
[typescript-eslint](https://typescript-eslint.io) for the Next.js
monorepo source code:

*
[`plugin:@typescript-eslint/recommended`](https://typescript-eslint.io/linting/configs#recommended):
Our base recommended rules that detect common bugs or _(non-stylistic)_
TypeScript bad practices
*
[`plugin:@typescript-eslint/stylistic`](https://typescript-eslint.io/linting/configs#stylistic):
Our base starting stylistic recommended for keeping codebases visually
consistent and avoiding out-of-practice visual constructs

The process I used is pretty standard (see
typescript-eslint/typescript-eslint#6760 for
other repos it was done on):

1. Enable those base recommended presets
2. Remove any rule settings that are now redundant
3. Reconfigure any rule whose default settings didn't seem to make sense
for this codebase
4. Add a `// Todo: ...` comment, and under it, add a disable for any
rule that immediately reported a lot of complaints

Note that this only enables the presets internally. It doesn't impact
what end-users of published packages such as Next.js or
`create-next-app` experience. That's a separate task in #52845.

I also didn't fix any existing warning from the `canary` branch. Would
you like me to do that? My preference would be a separate PR to get it
in more quickly.

Any code changes are commented inline.

---------

Co-authored-by: Steven <steven@ceriously.com>

.eslintrc.json

@@ -43,36 +43,51 @@
     },
     { "files": ["**/__tests__/**"], "env": { "jest": true } },
     {
+      "extends": [
+        "plugin:@typescript-eslint/recommended",
+        "plugin:@typescript-eslint/stylistic"
+      ],
       "files": ["**/*.ts", "**/*.tsx"],
       "parser": "@typescript-eslint/parser",
       "parserOptions": {
-        "ecmaVersion": 2018,
         "sourceType": "module",
-        "ecmaFeatures": {
-          "jsx": true
-        },
         "warnOnUnsupportedTypeScriptVersion": false
       },
       "plugins": ["@typescript-eslint"],
       "rules": {
-        // Already handled by TS
-        "no-dupe-class-members": "off",
-        "no-undef": "off",
-
-        // Add TypeScript specific rules (and turn off ESLint equivalents)
-        "@typescript-eslint/consistent-type-assertions": "warn",
-        "no-array-constructor": "off",
-        "@typescript-eslint/no-array-constructor": "warn",
+        // Todo: investigate, for each of these rules, whether we want them.
+        "@typescript-eslint/array-type": "off",
+        "@typescript-eslint/ban-ts-comment": "off",
+        "@typescript-eslint/ban-tslint-comment": "off",
+        "@typescript-eslint/ban-types": "off",
+        "@typescript-eslint/class-literal-property-style": "off",
+        "@typescript-eslint/consistent-generic-constructors": "off",
+        "@typescript-eslint/consistent-indexed-object-style": "off",
+        "@typescript-eslint/consistent-type-definitions": "off",
+        "@typescript-eslint/no-empty-function": "off",
         "@typescript-eslint/no-namespace": "off",
-        "no-use-before-define": "off",
-        "@typescript-eslint/no-use-before-define": [
-          "warn",
+        "@typescript-eslint/no-shadow": "off",
+        "@typescript-eslint/no-empty-interface": "off",
+        "@typescript-eslint/no-explicit-any": "off",
+        "@typescript-eslint/no-inferrable-types": "off",
+        "@typescript-eslint/no-var-requires": "off",
+        "@typescript-eslint/prefer-for-of": "off",
+        "@typescript-eslint/prefer-function-type": "off",
+        "@typescript-eslint/no-this-alias": "off",
+        "@typescript-eslint/triple-slash-reference": "off",
+        "no-var": "off",
+        "prefer-const": "off",
+        "prefer-rest-params": "off",
+        "prefer-spread": "off",
+
+        // These off- or differently-configured rules work well for us.
+        "no-unused-expressions": "off",
+        "@typescript-eslint/no-unused-expressions": [
+          "error",
           {
-            "functions": true,
-            "classes": true,
-            "variables": true,
-            "enums": true,
-            "typedefs": true
+            "allowShortCircuit": true,
+            "allowTernary": true,
+            "allowTaggedTemplates": true
           }
         ],
         "no-unused-vars": "off",
@@ -83,19 +98,20 @@
             "ignoreRestSiblings": true
           }
         ],
-        "no-unused-expressions": "off",
-        "@typescript-eslint/no-unused-expressions": [
-          "error",
+        "no-use-before-define": "off",
+        "@typescript-eslint/no-use-before-define": [
+          "warn",
           {
-            "allowShortCircuit": true,
-            "allowTernary": true,
-            "allowTaggedTemplates": true
+            "functions": true,
+            "classes": true,
+            "variables": true,
+            "enums": true,
+            "typedefs": true
           }
         ],
         "no-useless-constructor": "off",
         "@typescript-eslint/no-useless-constructor": "warn",
-        "@typescript-eslint/prefer-literal-enum-member": "error",
-        "@typescript-eslint/prefer-namespace-keyword": "error"
+        "@typescript-eslint/prefer-literal-enum-member": "error"
       },
       "overrides": [
         {

package.json

@@ -102,8 +102,8 @@
     "@types/sharp": "0.29.3",
     "@types/string-hash": "1.1.1",
     "@types/trusted-types": "2.0.3",
-    "@typescript-eslint/eslint-plugin": "4.29.1",
-    "@typescript-eslint/parser": "4.29.1",
+    "@typescript-eslint/eslint-plugin": "6.1.0",
+    "@typescript-eslint/parser": "6.1.0",
     "@vercel/fetch": "6.1.1",
     "@vercel/og": "0.5.9",
     "@zeit/next-typescript": "1.1.2-canary.0",

packages/eslint-plugin-next/src/utils/url.ts

@@ -77,7 +77,7 @@ export function getUrlFromPagesDirectories(
   })
 }
 
-export function execOnce<TArgs extends any[], TResult extends unknown>(
+export function execOnce<TArgs extends any[], TResult>(
   fn: (...args: TArgs) => TResult
 ): (...args: TArgs) => TResult {
   let used = false

packages/next-env/index.ts

@@ -80,6 +80,8 @@ export function processEnv(
           typeof parsed[key] === 'undefined' &&
           typeof origEnv[key] === 'undefined'
         ) {
+          // We're being imprecise in the type system - assume parsed[key] can be undefined
+          // eslint-disable-next-line @typescript-eslint/no-non-null-asserted-optional-chain
           parsed[key] = result.parsed?.[key]!
         }
       }

packages/next/src/build/webpack/plugins/middleware-plugin.ts

@@ -465,7 +465,7 @@ function getCodeAnalyzer(params: {
           buildInfo.importLocByPath = new Map()
         }
 
-        const importedModule = node.source.value?.toString()!
+        const importedModule = node.source.value?.toString()
         buildInfo.importLocByPath.set(importedModule, {
           sourcePosition: {
             ...node.loc.start,

packages/next/src/client/webpack.ts

@@ -1,4 +1,6 @@
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
 declare const __webpack_require__: any
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
 declare let __webpack_public_path__: string
 
 const addChunkSuffix =

packages/next/src/lib/metadata/types/metadata-interface.ts

@@ -562,6 +562,7 @@ type SitemapFile = Array<{
 
 type ResolvingMetadata = Promise<ResolvedMetadata>
 declare namespace MetadataRoute {
+  // eslint-disable-next-line @typescript-eslint/no-shadow
   export type Robots = RobotsFile
   export type Sitemap = SitemapFile
   export type Manifest = ManifestFile

packages/next/src/shared/lib/fnv1a.ts

@@ -1,6 +1,7 @@
 // source: https://github.com/sindresorhus/fnv1a
 // FNV_PRIMES and FNV_OFFSETS from
 // http://www.isthe.com/chongo/tech/comp/fnv/index.html#FNV-param
+/* eslint-disable @typescript-eslint/no-loss-of-precision */
 
 const FNV_PRIMES = {
   32: BigInt(16_777_619),