chore: tweak test config for hmr test run (#12423)

* conflict

* conflict

* lint

* add comments

* Update packages/svelte/tests/runtime-runes/samples/spread-props/_config.js

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

---------

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

packages/svelte/tests/runtime-legacy/samples/component-not-constructor2/_config.js

@@ -1,6 +1,11 @@
 import { test } from '../../test';
 
 export default test({
+	compileOptions: {
+		// override process.env.HMR — this test only passes in prod mode because in dev mode we generate a helpful error
+		dev: false
+	},
+
 	get props() {
 		return { componentName: 'Sub' };
 	},

packages/svelte/tests/runtime-legacy/shared.ts

@@ -138,11 +138,13 @@ export function runtime_suite(runes: boolean) {
 }
 
 async function common_setup(cwd: string, runes: boolean | undefined, config: RuntimeTest) {
+	const force_hmr = process.env.HMR && config.compileOptions?.dev !== false && !config.error;
+
 	const compileOptions: CompileOptions = {
 		generate: 'client',
 		rootDir: cwd,
-		dev: process.env.HMR ? true : undefined,
-		hmr: process.env.HMR ? true : undefined,
+		dev: force_hmr ? true : undefined,
+		hmr: force_hmr ? true : undefined,
 		...config.compileOptions,
 		immutable: config.immutable,
 		accessors: 'accessors' in config ? config.accessors : true,

packages/svelte/tests/runtime-runes/samples/bind-this-proxy/_config.js

@@ -2,6 +2,11 @@ import { flushSync } from 'svelte';
 import { test } from '../../test';
 
 export default test({
+	compileOptions: {
+		// override process.env.HMR — this test only passes in prod mode, because in dev we add `$destroy` methods etc
+		dev: false
+	},
+
 	html: `<button>Toggle</button><div>Hello\nworld</div>`,
 
 	async test({ assert, target, logs }) {