chore: validate promise handling (#11842)

* chore: don't swallow rejected promise errors

* ignore rules rather than adding catch blocks. add async to functions returning promises

* remove redundant asyncs

* remove extremely pointless rule

* remove another daft rule

* this is what typescript is for

* again, typescript already has this covered, we don't need it

* simplify

* this rule is harmless

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

eslint.config.js

@@ -5,10 +5,18 @@ import lube from 'eslint-plugin-lube';
 export default [
 	...svelte_config,
 	{
+		languageOptions: {
+			parserOptions: {
+				project: true
+			}
+		},
 		plugins: {
 			lube
 		},
 		rules: {
+			'@typescript-eslint/await-thenable': 'error',
+			'@typescript-eslint/prefer-promise-reject-errors': 'error',
+			'@typescript-eslint/require-await': 'error',
 			'no-console': 'error',
 			'lube/svelte-naming-convention': ['error', { fixSameNames: true }],
 			// eslint isn't that well-versed with JSDoc to know that `foo: /** @type{..} */ (foo)` isn't a violation of this rule, so turn it off
@@ -43,7 +51,6 @@ export default [
 			'documentation',
 			// contains a fork of the REPL which doesn't adhere to eslint rules
 			'sites/svelte-5-preview/**',
-			'playgrounds/demo/src/**',
 			'tmp/**',
 			// wasn't checked previously, reenable at some point
 			'sites/svelte.dev/**'

playgrounds/demo/.prettierignore

@@ -1 +0,0 @@
-src

playgrounds/demo/package.json

@@ -9,9 +9,7 @@
     "ssr": "node ./server.js",
     "build": "vite build --outDir dist/client && vite build --outDir dist/server --ssr src/entry-server.ts",
     "prod": "npm run build && node dist",
-    "preview": "vite preview",
-    "format": "prettier --check --write .",
-    "lint": "prettier --check . && eslint"
+    "preview": "vite preview"
   },
   "devDependencies": {
     "@sveltejs/vite-plugin-svelte": "^3.1.0",

playgrounds/sandbox/run.js

@@ -29,7 +29,7 @@ function mkdirp(dir) {
 const svelte_modules = glob('**/*.svelte', { cwd: `${cwd}/input` });
 const js_modules = glob('**/*.js', { cwd: `${cwd}/input` });
 
-for (const generate of ['client', 'server']) {
+for (const generate of /** @type {const} */ (['client', 'server'])) {
 	console.error(`\n--- generating ${generate} ---\n`);
 	for (const file of svelte_modules) {
 		const input = `${cwd}/input/${file}`;

playgrounds/sandbox/tsconfig.json

@@ -13,5 +13,5 @@
 		"allowJs": true,
 		"checkJs": true
 	},
-	"include": ["./input"]
+	"include": ["./run.js", "./input"]
 }