fix: Support experimental.async compiler option (#1438)

Author: baseballyama

.changeset/wild-steaks-invent.md

@@ -0,0 +1,5 @@
+---
+'eslint-plugin-svelte': patch
+---
+
+fix: Support `experimental.async` compiler option

packages/eslint-plugin-svelte/src/shared/svelte-compile-warns/index.ts

@@ -15,6 +15,7 @@ import type { IgnoreItem } from './ignore-comment.js';
 import { getSvelteIgnoreItems } from './ignore-comment.js';
 import { extractLeadingComments } from './extract-leading-comments.js';
 import { findAttribute, getLangValue } from '../../utils/ast-utils.js';
+import { getSvelteVersion } from '../../utils/svelte-context.js';
 import path from 'path';
 import fs from 'fs';
 
@@ -395,6 +396,8 @@ function isCustomElement(program: AST.SvelteProgram) {
 	});
 }
 
+const svelteVersion = getSvelteVersion();
+
 /**
  * Get compile warnings
  */
@@ -406,7 +409,16 @@ function getWarningsFromCode(
 	kind: 'warn' | 'error';
 } {
 	try {
+		const svelteConfig = context.sourceCode.parserServices.svelteParseContext?.svelteConfig;
+		const compilerOptions = svelteConfig?.compilerOptions ?? {};
 		const result = compiler.compile(code, {
+			...(svelteVersion === '5'
+				? {
+						experimental: {
+							async: compilerOptions.experimental?.async
+						}
+					}
+				: {}),
 			generate: false,
 			...(isCustomElement(context.sourceCode.ast) ? { customElement: true } : {})
 		});

packages/eslint-plugin-svelte/tests/fixtures/rules/valid-compile/invalid/experimental-async-disabled/top-level-await-errors.yaml

@@ -0,0 +1,6 @@
+- message: |-
+    Cannot use `await` in deriveds and template expressions, or at the top level of a component, unless the `experimental.async` compiler option is `true`
+    https://svelte.dev/e/experimental_async(experimental_async)
+  line: 2
+  column: 2
+  suggestions: null

packages/eslint-plugin-svelte/tests/fixtures/rules/valid-compile/invalid/experimental-async-disabled/top-level-await-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	await new Promise(() => {});
+</script>

packages/eslint-plugin-svelte/tests/fixtures/rules/valid-compile/invalid/experimental-async-disabled/top-level-await-requirements.json

@@ -0,0 +1,3 @@
+{
+	"svelte": ">=5.0.0-0"
+}

packages/eslint-plugin-svelte/tests/fixtures/rules/valid-compile/valid/svelte-config-experimental-async/_config.cjs

@@ -0,0 +1,13 @@
+module.exports = {
+	languageOptions: {
+		parserOptions: {
+			svelteConfig: {
+				compilerOptions: {
+					experimental: {
+						async: true
+					}
+				}
+			}
+		}
+	}
+};

packages/eslint-plugin-svelte/tests/fixtures/rules/valid-compile/valid/svelte-config-experimental-async/top-level-await-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	await new Promise(() => {});
+</script>

packages/eslint-plugin-svelte/tests/fixtures/rules/valid-compile/valid/svelte-config-experimental-async/top-level-await-requirements.json

@@ -0,0 +1,3 @@
+{
+	"svelte": ">=5.0.0-0"
+}