fix: cache call expressions in render tag arguments (#12418)

* fix: cache call expressions in render tag arguments

Ensure that they're called at most once per change, not once per access within the snippet
fixes #12187

* leverage state

* types

* fix

Author: dummdidumm

.changeset/tricky-avocados-play.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: cache call expressions in render tag arguments

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -600,7 +600,8 @@ function special(parser) {
 			end: parser.index,
 			expression: expression,
 			metadata: {
-				dynamic: false
+				dynamic: false,
+				args_with_call_expression: new Set()
 			}
 		});
 	}

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

@@ -8,7 +8,8 @@ import {
 	extract_paths,
 	is_event_attribute,
 	is_text_attribute,
-	object
+	object,
+	unwrap_optional
 } from '../../utils/ast.js';
 import * as b from '../../utils/builders.js';
 import { MathMLElements, ReservedKeywords, Runes, SVGElements } from '../constants.js';
@@ -441,6 +442,7 @@ export function analyze_component(root, source, options) {
 				has_props_rune: false,
 				component_slots: new Set(),
 				expression: null,
+				render_tag: null,
 				private_derived_state: [],
 				function_depth: scope.function_depth
 			};
@@ -512,6 +514,7 @@ export function analyze_component(root, source, options) {
 				reactive_statements: analysis.reactive_statements,
 				component_slots: new Set(),
 				expression: null,
+				render_tag: null,
 				private_derived_state: [],
 				function_depth: scope.function_depth
 			};
@@ -1289,14 +1292,26 @@ const common_visitors = {
 		}
 	},
 	CallExpression(node, context) {
-		const { expression } = context.state;
+		const { expression, render_tag } = context.state;
 		if (
 			(expression?.type === 'ExpressionTag' || expression?.type === 'SpreadAttribute') &&
 			!is_known_safe_call(node, context)
 		) {
 			expression.metadata.contains_call_expression = true;
 		}
 
+		if (render_tag) {
+			// Find out which of the render tag arguments contains this call expression
+			const arg_idx = unwrap_optional(render_tag.expression).arguments.findIndex(
+				(arg) => arg === node || context.path.includes(arg)
+			);
+
+			// -1 if this is the call expression of the render tag itself
+			if (arg_idx !== -1) {
+				render_tag.metadata.args_with_call_expression.add(arg_idx);
+			}
+		}
+
 		const callee = node.callee;
 		const rune = get_rune(node, context.state.scope);
 
@@ -1523,6 +1538,9 @@ const common_visitors = {
 		);
 
 		node.metadata.dynamic = binding !== null && binding.kind !== 'normal';
+	},
+	RenderTag(node, context) {
+		context.next({ ...context.state, render_tag: node });
 	}
 };
 

packages/svelte/src/compiler/phases/2-analyze/types.d.ts

@@ -3,6 +3,7 @@ import type { ComponentAnalysis, ReactiveStatement } from '../types.js';
 import type {
 	ClassDirective,
 	ExpressionTag,
+	RenderTag,
 	SpreadAttribute,
 	SvelteNode,
 	ValidatedCompileOptions
@@ -20,6 +21,8 @@ export interface AnalysisState {
 	component_slots: Set<string>;
 	/** The current {expression}, if any */
 	expression: ExpressionTag | ClassDirective | SpreadAttribute | null;
+	/** The current {@render ...} tag, if any */
+	render_tag: null | RenderTag;
 	private_derived_state: string[];
 	function_depth: number;
 }