[docs] Simplify paths for uncategorised pages (#1619)

This PR changes the paths that we use for uncategorised pages on the
docs site.
It also redirects the old paths to the new ones.

```
// BEFORE
tldraw.dev/docs/ucg/shapes

// AFTER
tldraw.dev/docs/shapes
```

I think that this is more intuitive, and will make the links that we
share a bit clearer.
eg: As a by-product, it fixes some broken links from the introduction
page.

As a trade-off, this PR makes our pathing system a bit more complicated.
But I don't think it's tooooo bad? WDYT?

### Change Type

- [x] `documentation` — Changes to the documentation only[^2]

[^1]: publishes a `patch` release, for devDependencies use `internal`
[^2]: will not publish a new version

### Test Plan

1. Navigate to `/docs/shapes` on the docs site.
2. Make sure that it goes to the Shapes page.
3. Do the same for `/docs/ucg/shapes`


### Release Notes

- Documentation: Cleaned up some paths.

apps/docs/next.config.js

@@ -5,6 +5,15 @@ const nextConfig = {
 		scrollRestoration: true,
 	},
 	transpilePackages: ['@tldraw/utils'],
+	async redirects() {
+		return [
+			{
+				source: '/:sectionId/ucg/:articleId',
+				destination: '/:sectionId/:articleId',
+				permanent: true,
+			},
+		]
+	},
 }
 
 module.exports = nextConfig

apps/docs/pages/[sectionId]/[childId]/[articleId].tsx

@@ -18,7 +18,8 @@ import { GetStaticPaths, GetStaticProps } from 'next'
 import { MDXRemoteSerializeResult } from 'next-mdx-remote'
 import { useTheme } from 'next-themes'
 
-interface Props {
+export type ArticleProps = {
+	type: 'article'
 	sidebar: SidebarContentList
 	section: Section
 	category: Category
@@ -34,7 +35,7 @@ export default function ArticlePage({
 	article,
 	links,
 	sidebar,
-}: Props) {
+}: ArticleProps) {
 	const theme = useTheme()
 	return (
 		<>
@@ -55,12 +56,13 @@ export default function ArticlePage({
 
 export const getStaticPaths: GetStaticPaths = async () => {
 	const sections = await getSections()
-	const paths: { params: { sectionId: string; categoryId: string; articleId: string } }[] = []
+	const paths: { params: { sectionId: string; childId: string; articleId: string } }[] = []
 
 	for (const section of sections) {
 		for (const category of section.categories) {
+			if (category.id === 'ucg') continue
 			for (const articleId of category.articleIds) {
-				paths.push({ params: { sectionId: section.id, categoryId: category.id, articleId } })
+				paths.push({ params: { sectionId: section.id, childId: category.id, articleId } })
 			}
 		}
 	}
@@ -68,9 +70,9 @@ export const getStaticPaths: GetStaticPaths = async () => {
 	return { paths, fallback: false }
 }
 
-export const getStaticProps: GetStaticProps<Props> = async (ctx) => {
+export const getStaticProps: GetStaticProps<ArticleProps> = async (ctx) => {
 	const sectionId = ctx.params?.sectionId?.toString() as string
-	const categoryId = ctx.params?.categoryId?.toString() as string
+	const categoryId = ctx.params?.childId?.toString() as string
 	const articleId = ctx.params?.articleId?.toString()
 	if (!articleId) throw Error()
 
@@ -81,5 +83,15 @@ export const getStaticProps: GetStaticProps<Props> = async (ctx) => {
 	const links = await getLinks(articleId)
 	const mdxSource = await getArticleSource(articleId)
 
-	return { props: { article, section, category, sidebar, links, mdxSource } }
+	return {
+		props: {
+			type: 'article',
+			article,
+			section,
+			category,
+			sidebar,
+			links,
+			mdxSource,
+		},
+	}
 }

apps/docs/pages/[sectionId]/[childId]/index.tsx

@@ -2,11 +2,14 @@ import { Breadcrumb } from '@/components/Breadcrumb'
 import { Mdx } from '@/components/Mdx'
 import { MetaHead } from '@/components/MetaHead'
 import { Sidebar } from '@/components/Sidebar'
+import ArticlePage from '@/pages/[sectionId]/[childId]/[articleId]'
 import { Article, Category, Section, SidebarContentList } from '@/types/content-types'
 import {
+	getArticle,
 	getArticleSource,
 	getArticles,
 	getCategory,
+	getLinks,
 	getSection,
 	getSections,
 } from '@/utils/content'
@@ -15,8 +18,10 @@ import { GetStaticPaths, GetStaticProps } from 'next'
 import { MDXRemoteSerializeResult } from 'next-mdx-remote'
 import { useTheme } from 'next-themes'
 import Link from 'next/link'
+import { ArticleProps } from './[articleId]'
 
-type Props = {
+type CategoryProps = {
+	type: 'category'
 	sidebar: SidebarContentList
 	section: Section
 	category: Category
@@ -24,15 +29,17 @@ type Props = {
 	mdxSource: MDXRemoteSerializeResult | null
 }
 
-export default function CategoryListPage({
-	sidebar,
-	mdxSource,
-	articles,
-	section,
-	category,
-}: Props) {
+type ChildProps = CategoryProps | ArticleProps
+
+export default function CategoryListPage(props: ChildProps) {
 	const theme = useTheme()
 
+	if (props.type === 'article') {
+		return <ArticlePage {...props} />
+	}
+
+	const { sidebar, section, category, articles, mdxSource } = props
+
 	const ungrouped: Article[] = []
 	const groupedArticles = Object.fromEntries(
 		category.groups.map((group) => [group.id, { group, articles: [] as Article[] }])
@@ -92,12 +99,18 @@ export default function CategoryListPage({
 
 export const getStaticPaths: GetStaticPaths = async () => {
 	const sections = await getSections()
-	const paths: { params: { sectionId: string; categoryId: string } }[] = []
+	const paths: { params: { sectionId: string; childId: string } }[] = []
 
 	for (const section of sections) {
 		if (section.categories) {
 			for (const category of section.categories) {
-				paths.push({ params: { sectionId: section.id, categoryId: category.id } })
+				paths.push({ params: { sectionId: section.id, childId: category.id } })
+
+				// Add paths for uncategorized articles as well
+				if (category.id !== 'ucg') continue
+				for (const articleId of category.articleIds) {
+					paths.push({ params: { sectionId: section.id, childId: articleId } })
+				}
 			}
 		}
 	}
@@ -105,23 +118,53 @@ export const getStaticPaths: GetStaticPaths = async () => {
 	return { paths, fallback: false }
 }
 
-export const getStaticProps: GetStaticProps<Props> = async (ctx) => {
+export const getStaticProps: GetStaticProps<ChildProps> = async (ctx) => {
 	const sectionId = ctx.params?.sectionId?.toString() as string
-	const categoryId = ctx.params?.categoryId?.toString()
-	if (!categoryId || !sectionId) throw Error()
-
-	const sidebar = await getSidebarContentList({
-		sectionId,
-		categoryId,
-	})
+	const childId = ctx.params?.childId?.toString()
+	if (!childId || !sectionId) throw Error()
 
 	const articles = await getArticles()
 	const section = await getSection(sectionId)
+
+	// If the path goes to an uncategorized article, show the article page
+	if (!section.categories.some((c) => c.id === childId)) {
+		const categoryId = 'ucg'
+		const articleId = childId
+		const sidebar = await getSidebarContentList({ sectionId, categoryId, articleId })
+		const category = await getCategory(sectionId, categoryId)
+		const article = await getArticle(articleId)
+		const links = await getLinks(articleId)
+		const mdxSource = await getArticleSource(articleId)
+		return {
+			props: {
+				type: 'article',
+				sidebar,
+				section,
+				category,
+				article,
+				links,
+				mdxSource,
+			},
+		}
+	}
+
+	// Otherwise, show the category page
+	const categoryId = childId
+	const sidebar = await getSidebarContentList({ sectionId, categoryId })
 	const category = await getCategory(sectionId, categoryId)
 	const categoryArticles = category.articleIds.map((id) => articles[id])
 
 	const article = articles[categoryId + '_index'] ?? null
 	const mdxSource = article ? await getArticleSource(categoryId + '_index') : null
 
-	return { props: { sidebar, section, category, articles: categoryArticles, mdxSource } }
+	return {
+		props: {
+			type: 'category',
+			sidebar,
+			section,
+			category,
+			articles: categoryArticles,
+			mdxSource,
+		},
+	}
 }