MD/MDX collect headings refactor (#5654)

1 files changed, 91 insertions, 0 deletions

diff --git a/packages/integrations/mdx/test/mdx-get-headings.test.js b/packages/integrations/mdx/test/mdx-get-headings.test.js
index 1ac7283dd..03290abc5 100644
--- a/packages/integrations/mdx/test/mdx-get-headings.test.js
+++ b/packages/integrations/mdx/test/mdx-get-headings.test.js
@@ -1,4 +1,6 @@
+import { rehypeHeadingIds } from '@astrojs/markdown-remark';
 import mdx from '@astrojs/mdx';
+import { visit } from 'unist-util-visit';
 
 import { expect } from 'chai';
 import { parseHTML } from 'linkedom';
@@ -58,3 +60,92 @@ describe('MDX getHeadings', () => {
 		);
 	});
 });
+
+describe('MDX heading IDs can be customized by user plugins', () => {
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: new URL('./fixtures/mdx-get-headings/', import.meta.url),
+			integrations: [mdx()],
+			markdown: {
+				rehypePlugins: [
+					() => (tree) => {
+						let count = 0;
+						visit(tree, 'element', (node, index, parent) => {
+							if (!/^h\d$/.test(node.tagName)) return;
+							if (!node.properties?.id) {
+								node.properties = { ...node.properties, id: String(count++) };
+							}
+						});
+					},
+				],
+			},
+		});
+
+		await fixture.build();
+	});
+
+	it('adds user-specified IDs to HTML output', async () => {
+		const html = await fixture.readFile('/test/index.html');
+		const { document } = parseHTML(html);
+
+		const h1 = document.querySelector('h1');
+		expect(h1?.textContent).to.equal('Heading test');
+		expect(h1?.getAttribute('id')).to.equal('0');
+
+		const headingIDs = document.querySelectorAll('h1,h2,h3').map((el) => el.id);
+		expect(JSON.stringify(headingIDs)).to.equal(
+			JSON.stringify(Array.from({ length: headingIDs.length }, (_, idx) => String(idx)))
+		);
+	});
+
+	it('generates correct getHeadings() export', async () => {
+		const { headingsByPage } = JSON.parse(await fixture.readFile('/pages.json'));
+		expect(JSON.stringify(headingsByPage['./test.mdx'])).to.equal(
+			JSON.stringify([
+				{ depth: 1, slug: '0', text: 'Heading test' },
+				{ depth: 2, slug: '1', text: 'Section 1' },
+				{ depth: 3, slug: '2', text: 'Subsection 1' },
+				{ depth: 3, slug: '3', text: 'Subsection 2' },
+				{ depth: 2, slug: '4', text: 'Section 2' },
+			])
+		);
+	});
+});
+
+describe('MDX heading IDs can be injected before user plugins', () => {
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: new URL('./fixtures/mdx-get-headings/', import.meta.url),
+			integrations: [
+				mdx({
+					rehypePlugins: [
+						rehypeHeadingIds,
+						() => (tree) => {
+							visit(tree, 'element', (node, index, parent) => {
+								if (!/^h\d$/.test(node.tagName)) return;
+								if (node.properties?.id) {
+									node.children.push({ type: 'text', value: ' ' + node.properties.id });
+								}
+							});
+						},
+					],
+				}),
+			],
+		});
+
+		await fixture.build();
+	});
+
+	it('adds user-specified IDs to HTML output', async () => {
+		const html = await fixture.readFile('/test/index.html');
+		const { document } = parseHTML(html);
+
+		const h1 = document.querySelector('h1');
+		expect(h1?.textContent).to.equal('Heading test heading-test');
+		expect(h1?.id).to.equal('heading-test');
+	});
+});