Add additional scoping for head buffering

.changeset/pretty-bananas-own.md

@@ -0,0 +1,10 @@
+---
+'astro': patch
+---
+
+Fix MDX related head placement bugs
+
+This fixes a variety of head content placement bugs (such as page `<link>`) related to MDX, especially when used in content collections. Issues fixed:
+
+- Head content being placed in the body instead of the head.
+- Head content missing when rendering an MDX component from within a nested Astro component.

packages/astro/package.json

@@ -99,7 +99,7 @@
     "test:e2e:match": "playwright test -g"
   },
   "dependencies": {
-    "@astrojs/compiler": "^1.0.1",
+    "@astrojs/compiler": "^1.1.0",
     "@astrojs/language-server": "^0.28.3",
     "@astrojs/markdown-remark": "^2.0.1",
     "@astrojs/telemetry": "^2.0.0",

packages/astro/src/content/internal.ts

@@ -4,6 +4,7 @@ import { prependForwardSlash } from '../core/path.js';
 import {
 	createComponent,
 	createHeadAndContent,
+	createScopedResult,
 	renderComponent,
 	renderScriptElement,
 	renderStyleElement,
@@ -169,7 +170,7 @@ async function render({
 
 			return createHeadAndContent(
 				unescapeHTML(styles + links + scripts) as any,
-				renderTemplate`${renderComponent(result, 'Content', mod.Content, props, slots)}`
+				renderTemplate`${renderComponent(createScopedResult(result), 'Content', mod.Content, props, slots)}`
 			);
 		},
 		propagation: 'self',

packages/astro/src/core/app/common.ts

@@ -14,10 +14,12 @@ export function deserializeManifest(serializedManifest: SerializedSSRManifest):
 	}
 
 	const assets = new Set<string>(serializedManifest.assets);
+	const propagation = new Map(serializedManifest.propagation);
 
 	return {
 		...serializedManifest,
 		assets,
+		propagation,
 		routes,
 	};
 }

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

@@ -193,6 +193,7 @@ export class App {
 				request,
 				origin: url.origin,
 				pathname,
+				propagation: this.#manifest.propagation,
 				scripts,
 				links,
 				route: routeData,

packages/astro/src/core/app/types.ts

@@ -1,9 +1,11 @@
 import type { MarkdownRenderingOptions } from '@astrojs/markdown-remark';
 import type {
 	ComponentInstance,
+	PropagationHint,
 	RouteData,
 	SerializedRouteData,
 	SSRLoadedRenderer,
+	SSRResult,
 } from '../../@types/astro';
 
 export type ComponentPath = string;
@@ -34,11 +36,13 @@ export interface SSRManifest {
 	renderers: SSRLoadedRenderer[];
 	entryModules: Record<string, string>;
 	assets: Set<string>;
+	propagation: SSRResult['propagation'];
 }
 
-export type SerializedSSRManifest = Omit<SSRManifest, 'routes' | 'assets'> & {
+export type SerializedSSRManifest = Omit<SSRManifest, 'routes' | 'assets' | 'propagation'> & {
 	routes: SerializedRouteInfo[];
 	assets: string[];
+	propagation: readonly [string, PropagationHint][];
 };
 
 export type AdapterCreateExports<T = any> = (

packages/astro/src/core/build/generate.ts

@@ -376,6 +376,7 @@ async function generatePath(
 		origin,
 		pathname,
 		request: createRequest({ url, headers: new Headers(), logging, ssr }),
+		propagation: internals.propagation,
 		scripts,
 		links,
 		route: pageData.route,

packages/astro/src/core/build/internal.ts

@@ -4,6 +4,7 @@ import type { PageBuildData, ViteID } from './types';
 import { PageOptions } from '../../vite-plugin-astro/types';
 import { prependForwardSlash, removeFileExtension } from '../path.js';
 import { viteID } from '../util.js';
+import { SSRResult } from '../../@types/astro';
 
 export interface BuildInternals {
 	/**
@@ -66,6 +67,7 @@ export interface BuildInternals {
 	staticFiles: Set<string>;
 	// The SSR entry chunk. Kept in internals to share between ssr/client build steps
 	ssrEntryChunk?: OutputChunk;
+	propagation: SSRResult['propagation'];
 }
 
 /**
@@ -95,6 +97,7 @@ export function createBuildInternals(): BuildInternals {
 		discoveredClientOnlyComponents: new Set(),
 		discoveredScripts: new Set(),
 		staticFiles: new Set(),
+		propagation: new Map(),
 	};
 }
 

packages/astro/src/core/build/plugins/index.ts

@@ -8,13 +8,15 @@ import { pluginInternals } from './plugin-internals.js';
 import { pluginPages } from './plugin-pages.js';
 import { pluginPrerender } from './plugin-prerender.js';
 import { pluginSSR } from './plugin-ssr.js';
+import { astroHeadPropagationBuildPlugin } from '../../../vite-plugin-head-propagation/index.js';
 
 export function registerAllPlugins({ internals, options, register }: AstroBuildPluginContainer) {
 	register(pluginAliasResolve(internals));
 	register(pluginAnalyzer(internals));
 	register(pluginInternals(internals));
 	register(pluginPages(options, internals));
 	register(pluginCSS(options, internals));
+	register(astroHeadPropagationBuildPlugin(options, internals));
 	register(pluginPrerender(options, internals));
 	register(astroConfigBuildPlugin(options, internals));
 	register(pluginHoistedScripts(options, internals));

packages/astro/src/core/build/plugins/plugin-ssr.ts

@@ -211,6 +211,7 @@ function buildManifest(
 			contentDir: getContentPaths(settings.config).contentDir,
 		},
 		pageMap: null as any,
+		propagation: Array.from(internals.propagation),
 		renderers: [],
 		entryModules,
 		assets: staticFiles.map((s) => settings.config.base + s),

packages/astro/src/core/compile/compile.ts

@@ -42,6 +42,7 @@ export async function compile({
 			sourcemap: 'both',
 			internalURL: 'astro/server/index.js',
 			astroGlobalArgs: JSON.stringify(astroConfig.site),
+			resultScopedSlot: true,
 			preprocessStyle: createStylePreprocessor({
 				filename,
 				viteConfig,

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

@@ -9,7 +9,7 @@ import type {
 	SSRLoadedRenderer,
 	SSRResult,
 } from '../../@types/astro';
-import { renderSlot, stringifyChunk } from '../../runtime/server/index.js';
+import { renderSlot, stringifyChunk, ScopeFlags, createScopedResult, ComponentSlots } from '../../runtime/server/index.js';
 import { renderJSX } from '../../runtime/server/jsx.js';
 import { AstroCookies } from '../cookies/index.js';
 import { AstroError, AstroErrorData } from '../errors/index.js';
@@ -55,10 +55,10 @@ function getFunctionExpression(slot: any) {
 
 class Slots {
 	#result: SSRResult;
-	#slots: Record<string, any> | null;
+	#slots: ComponentSlots | null;
 	#loggingOpts: LogOptions;
 
-	constructor(result: SSRResult, slots: Record<string, any> | null, logging: LogOptions) {
+	constructor(result: SSRResult, slots: ComponentSlots | null, logging: LogOptions) {
 		this.#result = result;
 		this.#slots = slots;
 		this.#loggingOpts = logging;
@@ -89,6 +89,7 @@ class Slots {
 	public async render(name: string, args: any[] = []) {
 		if (!this.#slots || !this.has(name)) return;
 
+		const scoped = createScopedResult(this.#result, ScopeFlags.RenderSlot);
 		if (!Array.isArray(args)) {
 			warn(
 				this.#loggingOpts,
@@ -97,26 +98,26 @@ class Slots {
 			);
 		} else if (args.length > 0) {
 			const slotValue = this.#slots[name];
-			const component = typeof slotValue === 'function' ? await slotValue() : await slotValue;
+			const component = typeof slotValue === 'function' ? await slotValue(scoped) : await slotValue;
 
 			// Astro
 			const expression = getFunctionExpression(component);
 			if (expression) {
-				const slot = expression(...args);
-				return await renderSlot(this.#result, slot).then((res) =>
+				const slot = () => expression(...args);
+				return await renderSlot(scoped, slot).then((res) =>
 					res != null ? String(res) : res
 				);
 			}
 			// JSX
 			if (typeof component === 'function') {
-				return await renderJSX(this.#result, component(...args)).then((res) =>
+				return await renderJSX(scoped, (component as any)(...args)).then((res) =>
 					res != null ? String(res) : res
 				);
 			}
 		}
 
-		const content = await renderSlot(this.#result, this.#slots[name]);
-		const outHTML = stringifyChunk(this.#result, content);
+		const content = await renderSlot(scoped, this.#slots[name]);
+		const outHTML = stringifyChunk(scoped, content);
 
 		return outHTML;
 	}

packages/astro/src/runtime/server/index.ts

@@ -5,10 +5,13 @@ export { escapeHTML, HTMLBytes, HTMLString, markHTMLString, unescapeHTML } from
 export { renderJSX } from './jsx.js';
 export {
 	addAttribute,
+	addScopeFlag,
 	createHeadAndContent,
+	createScopedResult,
 	defineScriptVars,
 	Fragment,
 	maybeRenderHead,
+	removeScopeFlag,
 	renderAstroTemplateResult as renderAstroComponent,
 	renderComponent,
 	renderComponentToIterable,
@@ -23,15 +26,15 @@ export {
 	renderTemplate,
 	renderToString,
 	renderUniqueStylesheet,
+	ScopeFlags,
 	stringifyChunk,
 	voidElementNames,
 } from './render/index.js';
 export type {
 	AstroComponentFactory,
 	AstroComponentInstance,
-	AstroComponentSlots,
-	AstroComponentSlotsWithValues,
 	RenderInstruction,
+	ComponentSlots
 } from './render/index.js';
 
 import { markHTMLString } from './escape.js';

packages/astro/src/runtime/server/jsx.ts

@@ -12,7 +12,7 @@ import {
 } from './index.js';
 import { HTMLParts } from './render/common.js';
 import type { ComponentIterable } from './render/component';
-import { ScopeFlags } from './render/util.js';
+import { createScopedResult, ScopeFlags } from './render/scope.js';
 
 const ClientOnlyPlaceholder = 'astro-client-only';
 
@@ -95,8 +95,9 @@ Did you forget to import the component or is it possible there is a typo?`);
 						props[key] = value;
 					}
 				}
-				result.scope |= ScopeFlags.JSX;
-				return markHTMLString(await renderToString(result, vnode.type as any, props, slots));
+				const scoped = createScopedResult(result, ScopeFlags.JSX);
+				const html = markHTMLString(await renderToString(scoped, vnode.type as any, props, slots));
+				return html;
 			}
 			case !vnode.type && (vnode.type as any) !== 0:
 				return '';

packages/astro/src/runtime/server/render/astro/factory.ts

@@ -3,7 +3,7 @@ import type { HeadAndContent } from './head-and-content';
 import type { RenderTemplateResult } from './render-template';
 
 import { HTMLParts } from '../common.js';
-import { ScopeFlags } from '../util.js';
+import { addScopeFlag, createScopedResult, ScopeFlags } from '../scope.js';
 import { isHeadAndContent } from './head-and-content.js';
 import { renderAstroTemplateResult } from './render-template.js';
 
@@ -28,8 +28,8 @@ export async function renderToString(
 	props: any,
 	children: any
 ): Promise<string> {
-	result.scope |= ScopeFlags.Astro;
-	const factoryResult = await componentFactory(result, props, children);
+	const scoped = createScopedResult(result, ScopeFlags.Astro);
+	const factoryResult = await componentFactory(scoped, props, children);
 
 	if (factoryResult instanceof Response) {
 		const response = factoryResult;

packages/astro/src/runtime/server/render/astro/index.ts

@@ -1,7 +1,7 @@
 export type { AstroComponentFactory } from './factory';
 export { isAstroComponentFactory, renderToString } from './factory.js';
 export { createHeadAndContent, isHeadAndContent } from './head-and-content.js';
-export type { AstroComponentInstance, ComponentSlots, ComponentSlotsWithValues } from './instance';
+export type { AstroComponentInstance } from './instance';
 export { createAstroComponentInstance, isAstroComponentInstance } from './instance.js';
 export {
 	isRenderTemplateResult,

packages/astro/src/runtime/server/render/astro/instance.ts

@@ -1,17 +1,15 @@
 import type { SSRResult } from '../../../../@types/astro';
 import type { AstroComponentFactory, AstroFactoryReturnValue } from './factory.js';
-import type { renderTemplate } from './render-template.js';
+import type { ComponentSlots } from '../slot.js';
 
 import { HydrationDirectiveProps } from '../../hydration.js';
 import { isPromise } from '../../util.js';
 import { renderChild } from '../any.js';
 import { isAPropagatingComponent } from './factory.js';
 import { isHeadAndContent } from './head-and-content.js';
+import { createScopedResult, ScopeFlags } from '../scope.js';
 
 type ComponentProps = Record<string | number, any>;
-type ComponentSlotValue = () => ReturnType<typeof renderTemplate>;
-export type ComponentSlots = Record<string, ComponentSlotValue>;
-export type ComponentSlotsWithValues = Record<string, ReturnType<ComponentSlotValue>>;
 
 const astroComponentInstanceSym = Symbol.for('astro.componentInstance');
 
@@ -20,7 +18,7 @@ export class AstroComponentInstance {
 
 	private readonly result: SSRResult;
 	private readonly props: ComponentProps;
-	private readonly slotValues: ComponentSlotsWithValues;
+	private readonly slotValues: ComponentSlots;
 	private readonly factory: AstroComponentFactory;
 	private returnValue: ReturnType<AstroComponentFactory> | undefined;
 	constructor(
@@ -33,19 +31,21 @@ export class AstroComponentInstance {
 		this.props = props;
 		this.factory = factory;
 		this.slotValues = {};
+		const scoped = createScopedResult(result, ScopeFlags.Slot);
 		for (const name in slots) {
-			this.slotValues[name] = slots[name]();
+			const value = slots[name](scoped);
+			this.slotValues[name] = () => value;
 		}
 	}
 
-	async init() {
-		this.returnValue = this.factory(this.result, this.props, this.slotValues);
+	async init(result: SSRResult) {
+		this.returnValue = this.factory(result, this.props, this.slotValues);
 		return this.returnValue;
 	}
 
 	async *render() {
 		if (this.returnValue === undefined) {
-			await this.init();
+			await this.init(this.result);
 		}
 
 		let value: AstroFactoryReturnValue | undefined = this.returnValue;

packages/astro/src/runtime/server/render/common.ts

@@ -10,6 +10,7 @@ import {
 } from '../scripts.js';
 import { renderAllHeadContent } from './head.js';
 import { isSlotString, type SlotString } from './slot.js';
+import { ScopeFlags } from './scope.js';
 
 export const Fragment = Symbol.for('astro:fragment');
 export const Renderer = Symbol.for('astro:renderer');
@@ -48,6 +49,30 @@ export function stringifyChunk(result: SSRResult, chunk: string | SlotString | R
 				}
 				return renderAllHeadContent(result);
 			}
+			case 'maybe-head': {
+				if (result._metadata.hasRenderedHead) {
+					return '';
+				}
+
+				const scope = instruction.scope;
+				switch (scope) {
+					// JSX with an Astro slot
+					case ScopeFlags.JSX | ScopeFlags.Slot | ScopeFlags.Astro:
+					case ScopeFlags.JSX | ScopeFlags.Astro | ScopeFlags.HeadBuffer:
+					case ScopeFlags.JSX |  ScopeFlags.Slot | ScopeFlags.Astro | ScopeFlags.HeadBuffer: {
+						return '';
+					}
+
+					// Astro.slots.render('default') should never render head content.
+					case ScopeFlags.RenderSlot | ScopeFlags.Astro:
+					case ScopeFlags.RenderSlot | ScopeFlags.Astro | ScopeFlags.JSX:
+					case ScopeFlags.RenderSlot | ScopeFlags.Astro | ScopeFlags.JSX | ScopeFlags.HeadBuffer: {
+						return '';
+					}
+				}
+
+				return renderAllHeadContent(result);
+			}
 		}
 	} else {
 		if (isSlotString(chunk as string)) {