fix(rendering): remove render instructions from slot expressions

.changeset/calm-mails-check.md

@@ -0,0 +1,5 @@
+---
+"astro": patch
+---
+
+Fixes an issue where functions could not be used as named slots.

packages/astro/src/core/render/index.ts

@@ -3,7 +3,7 @@ import type { Pipeline } from '../base-pipeline.js';
 export { Pipeline } from '../base-pipeline.js';
 export { getParams, getProps } from './params-and-props.js';
 export { loadRenderer } from './renderer.js';
-export { Slots } from './result.js';
+export { Slots } from './slots.js';
 
 export interface SSROptions {
 	/** The pipeline instance */

packages/astro/src/core/render/result.ts → packages/astro/src/core/render/slots.ts

@@ -2,13 +2,15 @@ import type { SSRResult } from '../../@types/astro.js';
 import { type ComponentSlots, renderSlotToString } from '../../runtime/server/index.js';
 import { renderJSX } from '../../runtime/server/jsx.js';
 import { chunkToString } from '../../runtime/server/render/index.js';
+import { isRenderInstruction } from '../../runtime/server/render/instruction.js';
 import { AstroError, AstroErrorData } from '../errors/index.js';
 import type { Logger } from '../logger/core.js';
 
 function getFunctionExpression(slot: any) {
 	if (!slot) return;
-	if (slot.expressions?.length !== 1) return;
-	return slot.expressions[0] as (...args: any[]) => any;
+	const expressions = slot?.expressions?.filter((e: unknown) => isRenderInstruction(e) === false);
+	if (expressions?.length !== 1) return
+	return expressions[0] as (...args: any[]) => any;
 }
 
 export class Slots {

packages/astro/src/runtime/server/render/astro/render-template.ts

@@ -11,7 +11,7 @@ const renderTemplateResultSym = Symbol.for('astro.renderTemplateResult');
 export class RenderTemplateResult {
 	public [renderTemplateResultSym] = true;
 	private htmlParts: TemplateStringsArray;
-	private expressions: any[];
+	public expressions: any[];
 	private error: Error | undefined;
 	constructor(htmlParts: TemplateStringsArray, expressions: unknown[]) {
 		this.htmlParts = htmlParts;

packages/astro/test/astro-slots.test.js

@@ -170,4 +170,15 @@ describe('Slots', () => {
 			assert.notEqual(third.children[0].data, first.children[0].data);
 		}
 	});
+
+	it("Arguments can be passed to named slots with Astro.slots.render()", async () => {
+		const html = await fixture.readFile('/slotted-named-functions/index.html');
+		const $ = cheerio.load(html);
+		const befor = $("div#before");
+		const [ beforeDiv ] = befor.children("div")
+		assert.deepEqual(beforeDiv.firstChild.data, "Test Content BEFORE")
+		const after = $("div#after");
+		const [ afterDiv ] = after.children("div");
+		assert.deepEqual(afterDiv.firstChild.data, "Test Content AFTER")
+	});
 });

packages/astro/test/fixtures/astro-slots/src/components/FunctionsToAPI.astro

@@ -0,0 +1,12 @@
+---
+const content = 'Test Content';
+const beforeConent = await Astro.slots.render("before", [{content}])
+const afterConent = await Astro.slots.render("after", [{content}])
+---
+<div id="before">
+  {beforeConent}
+</div>
+<div id="after">
+  {afterConent}
+</div>
+

packages/astro/test/fixtures/astro-slots/src/pages/slotted-named-functions.astro

@@ -0,0 +1,11 @@
+---
+import Field from '../components/FunctionsToAPI.astro'
+---
+<Field>
+  <div slot="before">
+    {({content}) => <div>{content} BEFORE</div>}
+  </div>
+  <div slot="after">
+    {({content}) => <div>{content} AFTER</div>}
+  </div>
+</Field>