withastro · matthewp · Oct 26, 2023 · Oct 5, 2023 · Oct 5, 2023 · Oct 5, 2023
diff --git a/.changeset/brave-pots-drop.md b/.changeset/brave-pots-drop.md
@@ -0,0 +1,18 @@
+---
+'astro': minor
+---
+
+Partials
+
+Any page component can now be identified as a *partial*, allowing you fetch them in the client in order to replace only parts of the page. Partials are used in conjuction with a rendering library, like htmx or Stimulus or even just jQuery.
+
+Pages marked as partials do not have a `doctype` or any head content included in the rendered result. You can mark any page as a partial by setting this option:
-Pages marked as partials do not have a `doctype` or any head content included in the rendered result. You can mark any page as a partial by setting this option:
+You can mark any `.astro` page as a partial with an export statement:
-Pages marked as partials do not have a `doctype` or any head content included in the rendered result. You can mark any page as a partial by setting this option:
+You can mark any `.astro` page as a partial with an export statement:
+
+
+```astro
+---
+export const partial = true;
+---
+
+<li>This is a single list item.</li>
+```
diff --git a/packages/astro/src/@types/astro.ts b/packages/astro/src/@types/astro.ts
@@ -1520,6 +1520,7 @@ export type AsyncRendererComponentFn<U> = (
 export interface ComponentInstance {
 	default: AstroComponentFactory;
 	css?: string[];
+	partial?: boolean;
 	prerender?: boolean;
 	/**
 	 * Only used for logging if deprecated drafts feature is used
@@ -2191,6 +2192,7 @@ export interface SSRResult {
 	 */
 	clientDirectives: Map<string, string>;
 	compressHTML: boolean;
+	partial: boolean;
 	/**
 	 * Only used for logging
 	 */

diff --git a/packages/astro/src/core/render/core.ts b/packages/astro/src/core/render/core.ts
@@ -49,6 +49,7 @@ export async function renderPage({ mod, renderContext, env, cookies }: RenderPag
 		clientDirectives: env.clientDirectives,
 		compressHTML: env.compressHTML,
 		request: renderContext.request,
+		partial: !!mod.partial,
 		site: env.site,
 		scripts: renderContext.scripts,
 		ssr: env.ssr,

diff --git a/packages/astro/src/core/render/result.ts b/packages/astro/src/core/render/result.ts
@@ -31,6 +31,7 @@ export interface CreateResultArgs {
 	renderers: SSRLoadedRenderer[];
 	clientDirectives: Map<string, string>;
 	compressHTML: boolean;
+	partial: boolean;
 	resolve: (s: string) => Promise<string>;
 	/**
 	 * Used for `Astro.site`
@@ -155,6 +156,7 @@ export function createResult(args: CreateResultArgs): SSRResult {
 		renderers: args.renderers,
 		clientDirectives: args.clientDirectives,
 		compressHTML: args.compressHTML,
+		partial: args.partial,
 		pathname: args.pathname,
 		cookies,
 		/** This function returns the `Astro` faux-global */

diff --git a/packages/astro/src/runtime/server/render/astro/render.ts b/packages/astro/src/runtime/server/render/astro/render.ts
@@ -33,7 +33,7 @@ export async function renderToString(
 			// Automatic doctype insertion for pages
 			if (isPage && !renderedFirstPageChunk) {
 				renderedFirstPageChunk = true;
-				if (!/<!doctype html/i.test(String(chunk))) {
+				if (!result.partial && !/<!doctype html/i.test(String(chunk))) {
 					const doctype = result.compressHTML ? '<!DOCTYPE html>' : '<!DOCTYPE html>\n';
 					str += doctype;
 				}
@@ -84,7 +84,7 @@ export async function renderToReadableStream(
 					// Automatic doctype insertion for pages
 					if (isPage && !renderedFirstPageChunk) {
 						renderedFirstPageChunk = true;
-						if (!/<!doctype html/i.test(String(chunk))) {
+						if (!result.partial && !/<!doctype html/i.test(String(chunk))) {
 							const doctype = result.compressHTML ? '<!DOCTYPE html>' : '<!DOCTYPE html>\n';
 							controller.enqueue(encoder.encode(doctype));
 						}

diff --git a/packages/astro/src/runtime/server/render/common.ts b/packages/astro/src/runtime/server/render/common.ts
@@ -77,13 +77,13 @@ function stringifyChunk(
 				}
 			}
 			case 'head': {
-				if (result._metadata.hasRenderedHead) {
+				if (result._metadata.hasRenderedHead || result.partial) {
 					return '';
 				}
 				return renderAllHeadContent(result);
 			}
 			case 'maybe-head': {
-				if (result._metadata.hasRenderedHead || result._metadata.headInTree) {
+				if (result._metadata.hasRenderedHead || result._metadata.headInTree || result.partial) {
 					return '';
 				}
 				return renderAllHeadContent(result);

diff --git a/packages/astro/src/runtime/server/render/component.ts b/packages/astro/src/runtime/server/render/component.ts
@@ -505,7 +505,7 @@ export async function renderComponentToString(
 				// Automatic doctype and head insertion for pages
 				if (isPage && !renderedFirstPageChunk) {
 					renderedFirstPageChunk = true;
-					if (!/<!doctype html/i.test(String(chunk))) {
+					if (!result.partial && !/<!doctype html/i.test(String(chunk))) {
 						const doctype = result.compressHTML ? '<!DOCTYPE html>' : '<!DOCTYPE html>\n';
 						str += doctype + head;
 					}

diff --git a/packages/astro/test/fixtures/partials/astro.config.mjs b/packages/astro/test/fixtures/partials/astro.config.mjs
@@ -0,0 +1,9 @@
+import { defineConfig } from 'astro/config';
+import mdx from '@astrojs/mdx';
+
+// https://astro.build/config
+export default defineConfig({
+	integrations: [
+		mdx()
+	]
+});
diff --git a/packages/astro/test/fixtures/partials/package.json b/packages/astro/test/fixtures/partials/package.json
@@ -0,0 +1,9 @@
+{
+  "name": "@test/partials",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*",
+    "@astrojs/mdx": "workspace:*"
+  }
+}
diff --git a/packages/astro/test/fixtures/partials/src/pages/partials/docs.mdx b/packages/astro/test/fixtures/partials/src/pages/partials/docs.mdx
@@ -0,0 +1,5 @@
+export const partial = true;
+
+# This is heading
+
+and this is some text
diff --git a/packages/astro/test/fixtures/partials/src/pages/partials/item.astro b/packages/astro/test/fixtures/partials/src/pages/partials/item.astro
@@ -0,0 +1,4 @@
+---
+export const partial = true;
+---
+<li>This is a single line item</li>
diff --git a/packages/astro/test/partials.test.js b/packages/astro/test/partials.test.js
@@ -0,0 +1,47 @@
+import { expect } from 'chai';
+import { loadFixture } from './test-utils.js';
+
+describe('Partials', () => {
+	/** @type {import('./test-utils.js').Fixture} */
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: './fixtures/partials/',
+		});
+	});
+
+	describe('dev', () => {
+		/** @type {import('./test-utils.js').DevServer} */
+		let devServer;
+
+		before(async () => {
+			devServer = await fixture.startDevServer();
+		});
+
+		after(async () => {
+			await devServer.stop();
+		});
+
+		it('is only the written HTML', async () => {
+			const html = await fixture.fetch('/partials/item/').then((res) => res.text());
+			expect(html.startsWith('<li>')).to.equal(true);
+		});
+	});
+
+	describe('build', () => {
+		before(async () => {
+			await fixture.build();
+		});
+
+		it('is only the written HTML', async () => {
+			const html = await fixture.readFile('/partials/item/index.html');
+			expect(html.startsWith('<li>')).to.equal(true);
+		});
+
+		it('Works with mdx', async () => {
+			const html = await fixture.readFile('/partials/docs/index.html');
+			expect(html.startsWith('<h1')).to.equal(true);
+		});
+	});
+});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml