feat: add stable route for all warning/error codes (#965)

* feat: add stable route for all warning/error codes

This establishes a new route `e/[code]` which serves as a stable reference for all of our warning/error codes. All links to warnings/errors from the Svelte compiler/runtime should go through this route in order to have stable references. That way we can move codes between warnings/errors/different pages or even adjust codes without breaking links.

Part of sveltejs/svelte#11305

* prerender entries

* work around Vercel's route limitation

* another workaround

Author: dummdidumm

apps/svelte.dev/src/lib/server/content.ts

@@ -60,16 +60,16 @@ export const blog_posts = index.blog.children
 		return a.date < b.date ? 1 : -1;
 	});
 
+export function remove_section(slug: string) {
+	return slug.replace(/\/[^/]+(\/[^/]+)$/g, '$1');
+}
+
 /**
  * Create docs index, which is basically the same structure as the original index
  * but with adjusted slugs (the section part is omitted for cleaner URLs), separated
  * topics/pages and next/prev adjusted so that they don't point to different topics.
  */
 function create_docs() {
-	function remove_section(slug: string) {
-		return slug.replace(/\/[^/]+(\/[^/]+)$/g, '$1');
-	}
-
 	let docs: {
 		/** The top level entries/packages: svelte/kit/etc. Key is the topic */
 		topics: Record<string, Document>;

apps/svelte.dev/src/routes/e/[code]/+page.server.ts

@@ -0,0 +1,40 @@
+import { remove_section } from '$lib/server/content';
+import { error, redirect } from '@sveltejs/kit';
+
+// All links to warnings/errors from the Svelte compiler/runtime go through this page in order to have stable references
+// (i.e. we can move codes between warnings/errors/different pages or even adjust codes without breaking links).
+
+// Right now we can't prerender this because we would hit a "too many routes" error on Vercel,
+// for which we need to implement https://github.com/sveltejs/kit/issues/9032
+// const reference = index['docs/svelte/reference'].children.filter(
+// 	(child) => child.slug.endsWith('-errors') || child.slug.endsWith('-warnings')
+// );
+//
+// export const prerender = true;
+//
+// export function entries() {
+// 	return reference.flatMap((page) =>
+// 		[...page.body.matchAll(/(^|\n)### (\w+)/g)].map(([, , code]) => ({ code }))
+// 	);
+// }
+
+export async function load({ params, fetch }) {
+	const codes: Record<string, Record<string, string[]>> = await fetch('/e/tmp/codes.json').then(
+		(r) => r.json()
+	);
+
+	for (const url of Object.keys(codes)) {
+		const page = codes[url];
+		for (const [h2, h3] of Object.entries(page)) {
+			if (h3.includes(params.code)) {
+				if (h2) {
+					redirect(307, `/${remove_section(url)}#${h2}-${params.code}`);
+				} else {
+					redirect(307, `/${remove_section(url)}#${params.code}`);
+				}
+			}
+		}
+	}
+
+	error(404, 'Not found');
+}

apps/svelte.dev/src/routes/e/tmp/codes.json/+server.ts

@@ -0,0 +1,39 @@
+import { index } from '$lib/server/content';
+import { json } from '@sveltejs/kit';
+
+// Temporary workaround for the problem described in [code]/+page.server.ts
+// In a nested folder because of https://github.com/sveltejs/kit/issues/12778
+
+const reference = index['docs/svelte/reference'].children.filter(
+	(child) => child.slug.endsWith('-errors') || child.slug.endsWith('-warnings')
+);
+
+// Since codes are not top level section we gotta jump through some hoops to get the right hash
+
+const codes: Record<string, Record<string, string[]>> = {};
+
+for (const page of reference) {
+	const grouped: Record<string, string[]> = {};
+	const sections = page.body.split(/(^|\n)## /g).slice(1);
+
+	for (const section of sections) {
+		const lines = section.slice(section.startsWith('\n') ? 1 : 0).split('\n');
+		const h2 = lines.shift()?.trim();
+
+		const h3_titles = lines
+			.filter((line) => line.startsWith('### '))
+			.map((line) => line.slice(4).trim());
+
+		if (h3_titles.length > 0) {
+			grouped[page.sections.find((s) => s.title === h2)?.slug ?? ''] = h3_titles;
+		}
+	}
+
+	codes[page.slug] = grouped;
+}
+
+export const prerender = true;
+
+export function GET() {
+	return json(codes);
+}