From 26c6d6f95d21de8cb524896b8433045ba0c7170d Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Thu, 7 Dec 2023 10:45:04 -0500
Subject: [PATCH] chore: avoid creating unnecessary thunks (#9841)

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/poor-seahorses-flash.md                    |  5 +++++
 packages/svelte/src/compiler/utils/builders.js        | 11 ++++++++++-
 .../_expected/client/main.svelte.js                   |  8 ++++----
 .../svelte-element/_expected/client/index.svelte.js   |  2 +-
 4 files changed, 20 insertions(+), 6 deletions(-)
 create mode 100644 .changeset/poor-seahorses-flash.md

diff --git a/.changeset/poor-seahorses-flash.md b/.changeset/poor-seahorses-flash.md
new file mode 100644
index 000000000000..4f6f146fe69a
--- /dev/null
+++ b/.changeset/poor-seahorses-flash.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+chore: avoid creating thunk for call expressions when appropriate
diff --git a/packages/svelte/src/compiler/utils/builders.js b/packages/svelte/src/compiler/utils/builders.js
index dd6cff6f9153..d98b840a195e 100644
--- a/packages/svelte/src/compiler/utils/builders.js
+++ b/packages/svelte/src/compiler/utils/builders.js
@@ -370,9 +370,18 @@ export function template(elements, expressions) {
 
 /**
  * @param {import('estree').Expression | import('estree').BlockStatement} expression
- * @returns {import('estree').ArrowFunctionExpression}
+ * @returns {import('estree').Expression}
  */
 export function thunk(expression) {
+	if (
+		expression.type === 'CallExpression' &&
+		expression.callee.type !== 'Super' &&
+		expression.callee.type !== 'MemberExpression' &&
+		expression.arguments.length === 0
+	) {
+		return expression.callee;
+	}
+
 	return arrow([], expression);
 }
 
diff --git a/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/client/main.svelte.js b/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/client/main.svelte.js
index 75d495c0a7fd..e233a9d51e0a 100644
--- a/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/client/main.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/client/main.svelte.js
@@ -21,9 +21,9 @@ export default function Main($$anchor, $$props) {
 	var custom_element_1 = $.sibling($.sibling(svg_1));
 
 	/* Update */
-	$.attr_effect(div, "foobar", () => y());
-	$.attr_effect(svg_1, "viewBox", () => y());
-	$.set_custom_element_data_effect(custom_element_1, "fooBar", () => y());
+	$.attr_effect(div, "foobar", y);
+	$.attr_effect(svg_1, "viewBox", y);
+	$.set_custom_element_data_effect(custom_element_1, "fooBar", y);
 
 	var node_foobar;
 	var svg_viewBox;
@@ -45,4 +45,4 @@ export default function Main($$anchor, $$props) {
 
 	$.close_frag($$anchor, fragment);
 	$.pop();
-}
\ No newline at end of file
+}
diff --git a/packages/svelte/tests/snapshot/samples/svelte-element/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/svelte-element/_expected/client/index.svelte.js
index ac61fc9e6d31..937e22410f67 100644
--- a/packages/svelte/tests/snapshot/samples/svelte-element/_expected/client/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/svelte-element/_expected/client/index.svelte.js
@@ -11,7 +11,7 @@ export default function Svelte_element($$anchor, $$props) {
 	var fragment = $.comment($$anchor);
 	var node = $.child_frag(fragment);
 
-	$.element(node, () => tag());
+	$.element(node, tag);
 	$.close_frag($$anchor, fragment);
 	$.pop();
 }