fix: import local plugins into markdown (#2534)

* Replaced "UnifiedPluginImport" for a function

* Updated tests

* Updated docs

* Updated examples

* Added changeset

* Fixed tests

* Removed unused "UnifiedPluginImport"

* Duplicated add-classes.mjs

9 files changed, 41 insertions, 22 deletions

diff --git a/.changeset/curly-wasps-sin.md b/.changeset/curly-wasps-sin.md
new file mode 100644
index 000000000..274738d66
--- /dev/null
+++ b/.changeset/curly-wasps-sin.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/markdown-remark': patch
+---
+
+Now you can use local plugins by passing a function instead of an `import`
diff --git a/docs/src/pages/en/guides/markdown-content.md b/docs/src/pages/en/guides/markdown-content.md
index b5e33d5b2..6eb80d5e1 100644
--- a/docs/src/pages/en/guides/markdown-content.md
+++ b/docs/src/pages/en/guides/markdown-content.md
@@ -69,6 +69,8 @@ export default {
 You can provide names of the plugins as well as import them:
 
 ```js
+import autolinkHeadings from 'remark-autolink-headings'
+
 // astro.config.mjs
 export default {
   markdownOptions: {
@@ -76,7 +78,7 @@ export default {
       '@astrojs/markdown-remark',
       {
         remarkPlugins: [
-          [import('remark-autolink-headings'), { behavior: 'prepend' }],
+          [autolinkHeadings, { behavior: 'prepend' }],
         ],
       },
     ],
diff --git a/examples/with-markdown-plugins/astro.config.mjs b/examples/with-markdown-plugins/astro.config.mjs
index 0fbb40de6..908b64cb0 100644
--- a/examples/with-markdown-plugins/astro.config.mjs
+++ b/examples/with-markdown-plugins/astro.config.mjs
@@ -6,6 +6,7 @@
 // helpful tooltips, and warnings if your exported object is invalid.
 // You can disable this by removing "@ts-check" and `@type` comments below.
 import astroRemark from '@astrojs/markdown-remark';
+import addClasses from './add-classes.mjs';
 
 // @ts-check
 export default /** @type {import('astro').AstroUserConfig} */ ({
@@ -15,12 +16,7 @@ export default /** @type {import('astro').AstroUserConfig} */ ({
 			astroRemark,
 			{
 				remarkPlugins: ['remark-code-titles'],
-				rehypePlugins: [
-					['rehype-autolink-headings', { behavior: 'prepend' }],
-					['rehype-toc', { headings: ['h2', 'h3'] }],
-					[new URL('./add-classes.mjs', import.meta.url).pathname, { 'h1,h2,h3': 'title' }],
-					'rehype-slug',
-				],
+				rehypePlugins: [['rehype-autolink-headings', { behavior: 'prepend' }], ['rehype-toc', { headings: ['h2', 'h3'] }], [addClasses, { 'h1,h2,h3': 'title' }], 'rehype-slug'],
 			},
 		],
 	},
diff --git a/packages/astro/package.json b/packages/astro/package.json
index 09df48cbe..ceac177e8 100644
--- a/packages/astro/package.json
+++ b/packages/astro/package.json
@@ -125,6 +125,7 @@
     "@types/yargs-parser": "^20.2.1",
     "chai": "^4.3.4",
     "cheerio": "^1.0.0-rc.10",
+    "hast-util-select": "^5.0.1",
     "mocha": "^9.1.3",
     "vite": "~2.6.10"
   },
diff --git a/packages/astro/test/astro-markdown-plugins.test.js b/packages/astro/test/astro-markdown-plugins.test.js
index aca9fcf7b..ee780a738 100644
--- a/packages/astro/test/astro-markdown-plugins.test.js
+++ b/packages/astro/test/astro-markdown-plugins.test.js
@@ -2,6 +2,7 @@ import { expect } from 'chai';
 import cheerio from 'cheerio';
 import { loadFixture } from './test-utils.js';
 import markdownRemark from '@astrojs/markdown-remark';
+import addClasses from './fixtures/astro-markdown-plugins/add-classes.mjs';
 
 describe('Astro Markdown plugins', () => {
 	let fixture;
@@ -15,11 +16,7 @@ describe('Astro Markdown plugins', () => {
 					markdownRemark,
 					{
 						remarkPlugins: ['remark-code-titles', ['rehype-autolink-headings', { behavior: 'prepend' }]],
-						rehypePlugins: [
-							[import('rehype-toc'), { headings: ['h2', 'h3'] }],
-							[import('../../../examples/with-markdown-plugins/add-classes.mjs'), { 'h1,h2,h3': 'title' }],
-							'rehype-slug',
-						],
+						rehypePlugins: [['rehype-toc', { headings: ['h2', 'h3'] }], [addClasses, { 'h1,h2,h3': 'title' }], 'rehype-slug'],
 					},
 				],
 			},
diff --git a/packages/astro/test/fixtures/astro-markdown-plugins/add-classes.mjs b/packages/astro/test/fixtures/astro-markdown-plugins/add-classes.mjs
new file mode 100644
index 000000000..39acabd52
--- /dev/null
+++ b/packages/astro/test/fixtures/astro-markdown-plugins/add-classes.mjs
@@ -0,0 +1,18 @@
+import { selectAll } from 'hast-util-select';
+
+export default (additions) => {
+	const adders = Object.entries(additions).map(adder);
+	return (node) => adders.forEach((a) => a(node));
+};
+
+const adder = ([selector, className]) => {
+	const writer = write(className);
+	return (node) => selectAll(selector, node).forEach(writer);
+};
+
+const write =
+	(className) =>
+	({ properties }) => {
+		if (!properties.className) properties.className = className;
+		else properties.className += ` ${className}`;
+	};
diff --git a/packages/markdown/remark/src/load-plugins.ts b/packages/markdown/remark/src/load-plugins.ts
index b1e72ae36..139eeaf19 100644
--- a/packages/markdown/remark/src/load-plugins.ts
+++ b/packages/markdown/remark/src/load-plugins.ts
@@ -1,26 +1,27 @@
 import * as unified from 'unified';
-import type { Plugin, UnifiedPluginImport } from './types';
+import type { Plugin } from './types';
 
-async function importPlugin(p: string | UnifiedPluginImport): UnifiedPluginImport {
+async function importPlugin(p: string | unified.Plugin): Promise<unified.Plugin> {
 	if (typeof p === 'string') {
-		return await import(p);
+		const importResult = await import(p);
+		return importResult.default;
 	}
 
-	return await p;
+	return p;
 }
 
-export function loadPlugins(items: Plugin[]): Promise<[unified.Plugin] | [unified.Plugin, any]>[] {
+export function loadPlugins(items: Plugin[]): Promise<[unified.Plugin, any?]>[] {
 	return items.map((p) => {
 		return new Promise((resolve, reject) => {
 			if (Array.isArray(p)) {
 				const [plugin, opts] = p;
 				return importPlugin(plugin)
-					.then((m) => resolve([m.default, opts]))
+					.then((m) => resolve([m, opts]))
 					.catch((e) => reject(e));
 			}
 
 			return importPlugin(p)
-				.then((m) => resolve([m.default]))
+				.then((m) => resolve([m]))
 				.catch((e) => reject(e));
 		});
 	});
diff --git a/packages/markdown/remark/src/types.ts b/packages/markdown/remark/src/types.ts
index 043594c9c..94c3e78a3 100644
--- a/packages/markdown/remark/src/types.ts
+++ b/packages/markdown/remark/src/types.ts
@@ -1,8 +1,7 @@
 import type * as unified from 'unified';
 import type * as shiki from 'shiki';
 
-export type UnifiedPluginImport = Promise<{ default: unified.Plugin }>;
-export type Plugin = string | [string, any] | UnifiedPluginImport | [UnifiedPluginImport, any];
+export type Plugin = string | [string, any] | unified.Plugin | [unified.Plugin, any];
 
 export interface AstroMarkdownOptions {
 	mode?: 'md' | 'mdx';
diff --git a/yarn.lock b/yarn.lock
index fce23a986..57fa86926 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4978,7 +4978,7 @@ hast-util-raw@^7.2.0:
     web-namespaces "^2.0.0"
     zwitch "^2.0.0"
 
-hast-util-select@5.0.1:
+hast-util-select@5.0.1, hast-util-select@^5.0.1:
   version "5.0.1"
   resolved "https://registry.yarnpkg.com/hast-util-select/-/hast-util-select-5.0.1.tgz#ed3788ad1a8d2d7f16a6bf8153ce9378edbe9d6d"
   integrity sha512-cxnImmR/tN/ipvbwGrKtEErmy83K1xWx8Bu7nImiwTOJ7X/fW1X6L1241ux+MYUXDwx8GxrE4LVmXRlEnbQsQA==