Codify parameter matching behaviour (#1373)

* test for split params ambiguous behaviour (#1268)

* docs

Author: Rich Harris

documentation/docs/01-routing.md

@@ -41,6 +41,8 @@ A file called either `src/routes/about.svelte` or `src/routes/about/index.svelte
 
 Dynamic parameters are encoded using `[brackets]`. For example, a blog post might be defined by `src/routes/blog/[slug].svelte`. Soon, we'll see how to access that parameter in a [load function](#loading) or the [page store](#modules-$app-stores).
 
+A file or directory can have multiple dynamic parts, like `[id]-[category].svelte`. (Paramters are 'non-greedy'; in an ambiguous case like `x-y-z`, `id` would be `x` and `category` would be `y-z`.)
+
 ### Endpoints
 
 Endpoints are modules written in `.js` (or `.ts`) files that export functions corresponding to HTTP methods. For example, our hypothetical blog page, `/blog/cool-article`, might request data from `/blog/cool-article.json`, which could be represented by a `src/routes/blog/[slug].json.js` endpoint:

packages/kit/test/apps/basics/src/routes/routing/__tests__.js

@@ -190,4 +190,14 @@ export default function (test) {
 		await clicknav('[href="/routing/fallthrough/potato"]');
 		assert.equal(await page.textContent('h1'), '404');
 	});
+
+	test(
+		'last parameter in a segment wins in cases of ambiguity',
+		'/routing/split-params',
+		async ({ page, clicknav }) => {
+			await clicknav('[href="/routing/split-params/x-y-z"]');
+			assert.equal(await page.textContent('h1'), 'x');
+			assert.equal(await page.textContent('h2'), 'y-z');
+		}
+	);
 }

packages/kit/test/apps/basics/src/routes/routing/split-params/[a]-[b].svelte

@@ -0,0 +1,6 @@
+<script>
+	import { page } from '$app/stores';
+</script>
+
+<h1>{$page.params.a}</h1>
+<h2>{$page.params.b}</h2>

packages/kit/test/apps/basics/src/routes/routing/split-params/index.svelte

@@ -0,0 +1 @@
+<a href="/routing/split-params/x-y-z">/routing/split-params/x-y-z</a>