Let remark plugins injected by Starlight plugins handle Markdown text and leaf directives (#2056)

4 files changed, 97 insertions, 6 deletions

diff --git a/.changeset/giant-dryers-fetch.md b/.changeset/giant-dryers-fetch.md
new file mode 100644
index 00000000..1d630146
--- /dev/null
+++ b/.changeset/giant-dryers-fetch.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/starlight': patch
+---
+
+Fixes an issue preventing remark plugins injected by Starlight plugins to handle Markdown text and leaf directives.
diff --git a/packages/starlight/__tests__/remark-rehype/asides.test.ts b/packages/starlight/__tests__/remark-rehype/asides.test.ts
index cb145e12..a46f8e0d 100644
--- a/packages/starlight/__tests__/remark-rehype/asides.test.ts
+++ b/packages/starlight/__tests__/remark-rehype/asides.test.ts
@@ -1,6 +1,8 @@
 import { createMarkdownProcessor } from '@astrojs/markdown-remark';
+import type { Root } from 'mdast';
+import { visit } from 'unist-util-visit';
 import { describe, expect, test } from 'vitest';
-import { starlightAsides } from '../../integrations/asides';
+import { starlightAsides, remarkDirectivesRestoration } from '../../integrations/asides';
 import { createTranslationSystemFromFs } from '../../utils/translations-fs';
 import { StarlightConfigSchema, type StarlightUserConfig } from '../../utils/user-config';
 
@@ -23,6 +25,9 @@ const processor = await createMarkdownProcessor({
 			astroConfig: { root: new URL(import.meta.url), srcDir: new URL('./_src/', import.meta.url) },
 			useTranslations,
 		}),
+		// The restoration plugin is run after the asides and any other plugin that may have been
+		// injected by Starlight plugins.
+		remarkDirectivesRestoration,
 	],
 });
 
@@ -167,13 +172,14 @@ test('runs without locales config', async () => {
 				},
 				useTranslations,
 			}),
+			remarkDirectivesRestoration,
 		],
 	});
 	const res = await processor.render(':::note\nTest\n::');
 	expect(res.code.includes('aria-label=Note"'));
 });
 
-test('tranforms back unhandled text directives', async () => {
+test('transforms back unhandled text directives', async () => {
 	const res = await processor.render(
 		`This is a:test of a sentence with a text:name[content]{key=val} directive.`
 	);
@@ -184,10 +190,47 @@ test('tranforms back unhandled text directives', async () => {
 	`);
 });
 
-test('tranforms back unhandled leaf directives', async () => {
+test('transforms back unhandled leaf directives', async () => {
 	const res = await processor.render(`::video[Title]{v=xxxxxxxxxxx}`);
 	expect(res.code).toMatchInlineSnapshot(`
 		"<p>::video[Title]{v="xxxxxxxxxxx"}
 		</p>"
 	`);
 });
+
+test('lets remark plugin injected by Starlight plugins handle text and leaf directives', async () => {
+	const processor = await createMarkdownProcessor({
+		remarkPlugins: [
+			...starlightAsides({
+				starlightConfig,
+				astroConfig: {
+					root: new URL(import.meta.url),
+					srcDir: new URL('./_src/', import.meta.url),
+				},
+				useTranslations,
+			}),
+			// A custom remark plugin injected by a Starlight plugin through an Astro integration would
+			// run before the restoration plugin.
+			function customRemarkPlugin() {
+				return function transformer(tree: Root) {
+					visit(tree, (node, index, parent) => {
+						if (node.type !== 'textDirective' || typeof index !== 'number' || !parent) return;
+						if (node.name === 'abbr') {
+							parent.children.splice(index, 1, { type: 'text', value: 'TEXT FROM REMARK PLUGIN' });
+						}
+					});
+				};
+			},
+			remarkDirectivesRestoration,
+		],
+	});
+
+	const res = await processor.render(
+		`This is a:test of a sentence with a :abbr[SL]{name="Starlight"} directive handled by another remark plugin and some other text:name[content]{key=val} directives not handled by any plugin.`
+	);
+	expect(res.code).toMatchInlineSnapshot(`
+		"<p>This is a:test
+		 of a sentence with a TEXT FROM REMARK PLUGIN directive handled by another remark plugin and some other text:name[content]{key="val"}
+		 directives not handled by any plugin.</p>"
+	`);
+});
diff --git a/packages/starlight/index.ts b/packages/starlight/index.ts
index a7876ab8..c13c03bc 100644
--- a/packages/starlight/index.ts
+++ b/packages/starlight/index.ts
@@ -3,7 +3,7 @@ import type { AstroIntegration } from 'astro';
 import { spawn } from 'node:child_process';
 import { dirname, relative } from 'node:path';
 import { fileURLToPath } from 'node:url';
-import { starlightAsides } from './integrations/asides';
+import { starlightAsides, starlightDirectivesRestorationIntegration } from './integrations/asides';
 import { starlightExpressiveCode } from './integrations/expressive-code/index';
 import { starlightSitemap } from './integrations/sitemap';
 import { vitePluginStarlightUserConfig } from './integrations/virtual-user-config';
@@ -73,6 +73,10 @@ export default function StarlightIntegration({
 				if (!allIntegrations.find(({ name }) => name === '@astrojs/mdx')) {
 					integrations.push(mdx({ optimize: true }));
 				}
+				// Add Starlight directives restoration integration at the end of the list so that remark
+				// plugins injected by Starlight plugins through Astro integrations can handle text and
+				// leaf directives before they are transformed back to their original form.
+				integrations.push(starlightDirectivesRestorationIntegration());
 
 				// Add integrations immediately after Starlight in the config array.
 				// e.g. if a user has `integrations: [starlight(), tailwind()]`, then the order will be
diff --git a/packages/starlight/integrations/asides.ts b/packages/starlight/integrations/asides.ts
index 2b03b372..3218e509 100644
--- a/packages/starlight/integrations/asides.ts
+++ b/packages/starlight/integrations/asides.ts
@@ -1,6 +1,6 @@
 /// <reference types="mdast-util-directive" />
 
-import type { AstroConfig, AstroUserConfig } from 'astro';
+import type { AstroConfig, AstroIntegration, AstroUserConfig } from 'astro';
 import { h as _h, s as _s, type Properties } from 'hastscript';
 import type { Node, Paragraph as P, Parent, Root } from 'mdast';
 import {
@@ -146,7 +146,6 @@ function remarkAsides(options: AsidesOptions): Plugin<[], Root> {
 				return;
 			}
 			if (node.type === 'textDirective' || node.type === 'leafDirective') {
-				transformUnhandledDirective(node, index, parent);
 				return;
 			}
 			const variant = node.name;
@@ -210,3 +209,43 @@ type RemarkPlugins = NonNullable<NonNullable<AstroUserConfig['markdown']>['remar
 export function starlightAsides(options: AsidesOptions): RemarkPlugins {
 	return [remarkDirective, remarkAsides(options)];
 }
+
+export function remarkDirectivesRestoration() {
+	return function transformer(tree: Root) {
+		visit(tree, (node, index, parent) => {
+			if (
+				index !== undefined &&
+				parent &&
+				(node.type === 'textDirective' || node.type === 'leafDirective')
+			) {
+				transformUnhandledDirective(node, index, parent);
+				return;
+			}
+		});
+	};
+}
+
+/**
+ * Directives not handled by Starlight are transformed back to their original form to avoid
+ * breaking user content.
+ * To allow remark plugins injected by Starlight plugins through Astro integrations to handle
+ * such directives, we need to restore unhandled text and leaf directives back to their original
+ * form only after all these other plugins have run.
+ * To do so, we run a remark plugin restoring these directives back to their original form from
+ * another Astro integration that runs after all the ones that may have been injected by Starlight
+ * plugins.
+ */
+export function starlightDirectivesRestorationIntegration(): AstroIntegration {
+	return {
+		name: 'starlight-directives-restoration',
+		hooks: {
+			'astro:config:setup': ({ updateConfig }) => {
+				updateConfig({
+					markdown: {
+						remarkPlugins: [remarkDirectivesRestoration],
+					},
+				});
+			},
+		},
+	};
+}