fix: handle ts expressions when dealing with runes (#9681)

* fix: handle ts expressions when dealing with runes

related to #9639

* docs, more tests

* simplify

---------

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

Author: dummdidumm

.changeset/twelve-onions-juggle.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: handle ts expressions when dealing with runes

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -7,7 +7,8 @@ import {
 	extract_paths,
 	is_event_attribute,
 	is_text_attribute,
-	object
+	object,
+	unwrap_ts_expression
 } from '../../utils/ast.js';
 import * as b from '../../utils/builders.js';
 import { ReservedKeywords, Runes, SVGElements } from '../constants.js';
@@ -660,10 +661,11 @@ const runes_scope_js_tweaker = {
 /** @type {import('./types').Visitors} */
 const runes_scope_tweaker = {
 	VariableDeclarator(node, { state }) {
-		if (node.init?.type !== 'CallExpression') return;
-		if (get_rune(node.init, state.scope) === null) return;
+		const init = unwrap_ts_expression(node.init);
+		if (!init || init.type !== 'CallExpression') return;
+		if (get_rune(init, state.scope) === null) return;
 
-		const callee = node.init.callee;
+		const callee = init.callee;
 		if (callee.type !== 'Identifier') return;
 
 		const name = callee.name;

packages/svelte/src/compiler/phases/2-analyze/validation.js

@@ -1,5 +1,10 @@
 import { error } from '../../errors.js';
-import { extract_identifiers, is_text_attribute } from '../../utils/ast.js';
+import {
+	extract_identifiers,
+	get_parent,
+	is_text_attribute,
+	unwrap_ts_expression
+} from '../../utils/ast.js';
 import { warn } from '../../warnings.js';
 import fuzzymatch from '../1-parse/utils/fuzzymatch.js';
 import { binding_properties } from '../bindings.js';
@@ -491,7 +496,7 @@ function validate_call_expression(node, scope, path) {
 	const rune = get_rune(node, scope);
 	if (rune === null) return;
 
-	const parent = /** @type {import('#compiler').SvelteNode} */ (path.at(-1));
+	const parent = /** @type {import('#compiler').SvelteNode} */ (get_parent(path, -1));
 
 	if (rune === '$props') {
 		if (parent.type === 'VariableDeclarator') return;
@@ -703,7 +708,7 @@ export const validation_runes = merge(validation, a11y_validators, {
 		next({ ...state });
 	},
 	VariableDeclarator(node, { state }) {
-		const init = node.init;
+		const init = unwrap_ts_expression(node.init);
 		const rune = get_rune(init, state.scope);
 
 		if (rune === null) return;

packages/svelte/src/compiler/phases/3-transform/client/visitors/javascript-runes.js

@@ -3,6 +3,7 @@ import { is_hoistable_function } from '../../utils.js';
 import * as b from '../../../../utils/builders.js';
 import * as assert from '../../../../utils/assert.js';
 import { create_state_declarators, get_props_method } from '../utils.js';
+import { unwrap_ts_expression } from '../../../../utils/ast.js';
 
 /** @type {import('../types.js').ComponentVisitors} */
 export const javascript_visitors_runes = {
@@ -133,7 +134,7 @@ export const javascript_visitors_runes = {
 		const declarations = [];
 
 		for (const declarator of node.declarations) {
-			const init = declarator.init;
+			const init = unwrap_ts_expression(declarator.init);
 			const rune = get_rune(init, state.scope);
 			if (!rune || rune === '$effect.active' || rune === '$effect.root') {
 				if (init != null && is_hoistable_function(init)) {
@@ -208,7 +209,8 @@ export const javascript_visitors_runes = {
 				// TODO
 				continue;
 			}
-			const args = /** @type {import('estree').CallExpression} */ (declarator.init).arguments;
+
+			const args = /** @type {import('estree').CallExpression} */ (init).arguments;
 			const value =
 				args.length === 0
 					? b.id('undefined')

packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

@@ -1,6 +1,11 @@
 import { walk } from 'zimmerframe';
 import { set_scope, get_rune } from '../../scope.js';
-import { extract_identifiers, extract_paths, is_event_attribute } from '../../../utils/ast.js';
+import {
+	extract_identifiers,
+	extract_paths,
+	is_event_attribute,
+	unwrap_ts_expression
+} from '../../../utils/ast.js';
 import * as b from '../../../utils/builders.js';
 import is_reference from 'is-reference';
 import {
@@ -568,7 +573,8 @@ const javascript_visitors_runes = {
 		const declarations = [];
 
 		for (const declarator of node.declarations) {
-			const rune = get_rune(declarator.init, state.scope);
+			const init = unwrap_ts_expression(declarator.init);
+			const rune = get_rune(init, state.scope);
 			if (!rune || rune === '$effect.active') {
 				declarations.push(/** @type {import('estree').VariableDeclarator} */ (visit(declarator)));
 				continue;
@@ -579,7 +585,7 @@ const javascript_visitors_runes = {
 				continue;
 			}
 
-			const args = /** @type {import('estree').CallExpression} */ (declarator.init).arguments;
+			const args = /** @type {import('estree').CallExpression} */ (init).arguments;
 			const value =
 				args.length === 0
 					? b.id('undefined')

packages/svelte/src/compiler/utils/ast.js

@@ -265,3 +265,42 @@ function _extract_paths(assignments = [], param, expression, update_expression)
 
 	return assignments;
 }
+
+/**
+ * The Acorn TS plugin defines `foo!` as a `TSNonNullExpression` node, and
+ * `foo as Bar` as a `TSAsExpression` node. This function unwraps those.
+ *
+ * @template {import('#compiler').SvelteNode | undefined | null} T
+ * @param {T} node
+ * @returns {T}
+ */
+export function unwrap_ts_expression(node) {
+	if (!node) {
+		return node;
+	}
+
+	// @ts-expect-error these types don't exist on the base estree types
+	if (node.type === 'TSNonNullExpression' || node.type === 'TSAsExpression') {
+		// @ts-expect-error
+		return node.expression;
+	}
+
+	return node;
+}
+
+/**
+ * Like `path.at(x)`, but skips over `TSNonNullExpression` and `TSAsExpression` nodes and eases assertions a bit
+ * by removing the `| undefined` from the resulting type.
+ *
+ * @template {import('#compiler').SvelteNode} T
+ * @param {T[]} path
+ * @param {number} at
+ */
+export function get_parent(path, at) {
+	let node = path.at(at);
+	// @ts-expect-error
+	if (node.type === 'TSNonNullExpression' || node.type === 'TSAsExpression') {
+		return /** @type {T} */ (path.at(at < 0 ? at - 1 : at + 1));
+	}
+	return /** @type {T} */ (node);
+}

packages/svelte/tests/runtime-runes/samples/typescript-as-expression/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: '1 2'
+});

packages/svelte/tests/runtime-runes/samples/typescript-as-expression/main.svelte

@@ -0,0 +1,6 @@
+<script lang="ts">
+	let count = $state(1) as number;
+	let double = $derived(count as number * 2) as number;
+</script>
+
+{count as number} {double as number}

packages/svelte/tests/runtime-runes/samples/typescript-non-null-expression/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: '1 2'
+});

packages/svelte/tests/runtime-runes/samples/typescript-non-null-expression/main.svelte

@@ -0,0 +1,6 @@
+<script lang="ts">
+	let count = $state(1)!;
+	let double = $derived(count! * 2)!;
+</script>
+
+{count!} {double!}