From b570d3ce943efaeebf7e8cc219e27a4815e880a6 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 16:42:11 -0500
Subject: [PATCH 01/20] add failing test for #7548

---
 .../routes/routing/optional-then-rest/+layout.svelte |  4 ++++
 .../routes/routing/optional-then-rest/+page.svelte   |  0
 .../[[x=numeric]]/[...y]/+page.svelte                |  6 ++++++
 packages/kit/test/apps/basics/test/test.js           | 12 ++++++++++++
 4 files changed, 22 insertions(+)
 create mode 100644 packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte
 create mode 100644 packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+page.svelte
 create mode 100644 packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte

diff --git a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte
new file mode 100644
index 000000000000..023662db9505
--- /dev/null
+++ b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte
@@ -0,0 +1,4 @@
+<a href="/routing/optional-then-rest/a/1">/routing/optional-then-rest/a/1</a>
+<a href="/routing/optional-then-rest/1/2">/routing/optional-then-rest/1/2</a>
+
+<slot />
diff --git a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+page.svelte b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+page.svelte
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte
new file mode 100644
index 000000000000..3ceb365c4a89
--- /dev/null
+++ b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte
@@ -0,0 +1,6 @@
+<script>
+	import { page } from '$app/stores';
+</script>
+
+<p data-testid="x">{$page.params.x}</p>
+<p data-testid="y">{$page.params.y}</p>
diff --git a/packages/kit/test/apps/basics/test/test.js b/packages/kit/test/apps/basics/test/test.js
index be47fcb68a93..2c65e444b476 100644
--- a/packages/kit/test/apps/basics/test/test.js
+++ b/packages/kit/test/apps/basics/test/test.js
@@ -1686,6 +1686,18 @@ test.describe('Routing', () => {
 		expect(await page.textContent('p')).toBe('This is your custom error page saying: "Not Found"');
 	});
 
+	test('allows optional parameter before a rest parameter', async ({ page, clicknav }) => {
+		await page.goto('/routing/optional-then-rest');
+
+		await clicknav('[href="/routing/optional-then-rest/a/1"]');
+		expect(await page.textContent('[data-testid="x"]')).toBe('undefined');
+		expect(await page.textContent('[data-testid="y"]')).toBe('a/1');
+
+		await clicknav('[href="/routing/optional-then-rest/1/2"]');
+		expect(await page.textContent('[data-testid="x"]')).toBe('1');
+		expect(await page.textContent('[data-testid="y"]')).toBe('2');
+	});
+
 	if (process.platform !== 'win32') {
 		test('Respects symlinks', async ({ page, clicknav }) => {
 			await page.goto('/routing');

From b29fd0f84d48b3d2aaf6e33cd83fa5b3d9ab304c Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 16:42:38 -0500
Subject: [PATCH 02/20] refactor

---
 .../kit/src/core/generate_manifest/index.js   |  8 +--
 .../core/sync/create_manifest_data/index.js   | 10 +---
 .../kit/src/core/sync/write_types/index.js    |  8 +--
 packages/kit/src/exports/vite/dev/index.js    |  4 +-
 packages/kit/src/runtime/client/parse.js      |  4 +-
 packages/kit/src/runtime/server/index.js      |  2 +-
 packages/kit/src/utils/routing.js             | 59 ++++++++-----------
 packages/kit/src/utils/routing.spec.js        | 53 ++++++-----------
 packages/kit/types/internal.d.ts              | 14 ++---
 9 files changed, 62 insertions(+), 100 deletions(-)

diff --git a/packages/kit/src/core/generate_manifest/index.js b/packages/kit/src/core/generate_manifest/index.js
index 429fd27cca1a..a77685b964ca 100644
--- a/packages/kit/src/core/generate_manifest/index.js
+++ b/packages/kit/src/core/generate_manifest/index.js
@@ -99,8 +99,8 @@ export function generate_manifest({ build_data, relative_path, routes, format =
 			],
 			routes: [
 				${routes.map(route => {
-					route.types.forEach(type => {
-						if (type) matchers.add(type);
+					route.params.forEach(param => {
+						if (param.matcher) matchers.add(param.matcher);
 					});
 
 					if (!route.page && !route.endpoint) return;
@@ -108,9 +108,7 @@ export function generate_manifest({ build_data, relative_path, routes, format =
 					return `{
 					id: ${s(route.id)},
 					pattern: ${route.pattern},
-					names: ${s(route.names)},
-					types: ${s(route.types)},
-					optional: ${s(route.optional)},
+					params: ${s(route.params)},
 					page: ${route.page ? `{ layouts: ${get_nodes(route.page.layouts)}, errors: ${get_nodes(route.page.errors)}, leaf: ${reindexed.get(route.page.leaf)} }` : 'null'},
 					endpoint: ${route.endpoint ? loader(join_relative(relative_path, resolve_symlinks(build_data.server.vite_manifest, route.endpoint.file).chunk.file)) : 'null'}
 				}`;
diff --git a/packages/kit/src/core/sync/create_manifest_data/index.js b/packages/kit/src/core/sync/create_manifest_data/index.js
index bd797a9aea32..96f5ff503d84 100644
--- a/packages/kit/src/core/sync/create_manifest_data/index.js
+++ b/packages/kit/src/core/sync/create_manifest_data/index.js
@@ -153,7 +153,7 @@ function create_routes_and_nodes(cwd, config, fallback) {
 				);
 			}
 
-			const { pattern, names, types, optional } = parse_route_id(id);
+			const { pattern, params } = parse_route_id(id);
 
 			/** @type {import('types').RouteData} */
 			const route = {
@@ -162,9 +162,7 @@ function create_routes_and_nodes(cwd, config, fallback) {
 
 				segment,
 				pattern,
-				names,
-				types,
-				optional,
+				params,
 
 				layout: null,
 				error: null,
@@ -273,9 +271,7 @@ function create_routes_and_nodes(cwd, config, fallback) {
 			id: '/',
 			segment: '',
 			pattern: /^$/,
-			names: [],
-			types: [],
-			optional: [],
+			params: [],
 			parent: null,
 			layout: null,
 			error: null,
diff --git a/packages/kit/src/core/sync/write_types/index.js b/packages/kit/src/core/sync/write_types/index.js
index 17cb181256ae..a10a654b5cc4 100644
--- a/packages/kit/src/core/sync/write_types/index.js
+++ b/packages/kit/src/core/sync/write_types/index.js
@@ -195,8 +195,8 @@ function update_types(config, routes, route, to_delete = new Set()) {
 	// Makes sure a type is "repackaged" and therefore more readable
 	declarations.push('type Expand<T> = T extends infer O ? { [K in keyof O]: O[K] } : never;');
 	declarations.push(
-		`type RouteParams = { ${route.names
-			.map((param, idx) => `${param}${route.optional[idx] ? '?' : ''}: string`)
+		`type RouteParams = { ${route.params
+			.map((param) => `${param.name}${param.optional ? '?' : ''}: string`)
 			.join('; ')} }`
 	);
 
@@ -270,8 +270,8 @@ function update_types(config, routes, route, to_delete = new Set()) {
 			if (leaf) {
 				if (leaf.route.page) ids.push(`"${leaf.route.id}"`);
 
-				for (const name of leaf.route.names) {
-					layout_params.add(name);
+				for (const param of leaf.route.params) {
+					layout_params.add(param.name);
 				}
 
 				ensureProxies(page, leaf.proxies);
diff --git a/packages/kit/src/exports/vite/dev/index.js b/packages/kit/src/exports/vite/dev/index.js
index 6684163a5df5..7feaa7cfec3a 100644
--- a/packages/kit/src/exports/vite/dev/index.js
+++ b/packages/kit/src/exports/vite/dev/index.js
@@ -156,9 +156,7 @@ export async function dev(vite, vite_config, svelte_config) {
 						return {
 							id: route.id,
 							pattern: route.pattern,
-							names: route.names,
-							types: route.types,
-							optional: route.optional,
+							params: route.params,
 							page: route.page,
 							endpoint: endpoint
 								? async () => {
diff --git a/packages/kit/src/runtime/client/parse.js b/packages/kit/src/runtime/client/parse.js
index 63909d0fcf8f..b452e3b87604 100644
--- a/packages/kit/src/runtime/client/parse.js
+++ b/packages/kit/src/runtime/client/parse.js
@@ -11,14 +11,14 @@ export function parse(nodes, server_loads, dictionary, matchers) {
 	const layouts_with_server_load = new Set(server_loads);
 
 	return Object.entries(dictionary).map(([id, [leaf, layouts, errors]]) => {
-		const { pattern, names, types, optional } = parse_route_id(id);
+		const { pattern, params } = parse_route_id(id);
 
 		const route = {
 			id,
 			/** @param {string} path */
 			exec: (path) => {
 				const match = pattern.exec(path);
-				if (match) return exec(match, { names, types, optional }, matchers);
+				if (match) return exec(match, params, matchers);
 			},
 			errors: [1, ...(errors || [])].map((n) => nodes[n]),
 			layouts: [0, ...(layouts || [])].map(create_layout_loader),
diff --git a/packages/kit/src/runtime/server/index.js b/packages/kit/src/runtime/server/index.js
index 18a9fe003395..f5554c4c64cf 100644
--- a/packages/kit/src/runtime/server/index.js
+++ b/packages/kit/src/runtime/server/index.js
@@ -77,7 +77,7 @@ export async function respond(request, options, state) {
 			const match = candidate.pattern.exec(decoded);
 			if (!match) continue;
 
-			const matched = exec(match, candidate, matchers);
+			const matched = exec(match, candidate.params, matchers);
 			if (matched) {
 				route = candidate;
 				params = decode_params(matched);
diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 7991499df119..eb119a97b94e 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -5,14 +5,8 @@ const param_pattern = /^(\[)?(\.\.\.)?(\w+)(?:=(\w+))?(\])?$/;
  * @param {string} id
  */
 export function parse_route_id(id) {
-	/** @type {string[]} */
-	const names = [];
-
-	/** @type {string[]} */
-	const types = [];
-
-	/** @type {boolean[]} */
-	const optional = [];
+	/** @type {Array<{ name: string, matcher: string, optional: boolean }>} */
+	const params = [];
 
 	// `/foo` should get an optional trailing slash, `/foo.json` should not
 	// const add_trailing_slash = !/\.[a-z]+$/.test(key);
@@ -27,17 +21,17 @@ export function parse_route_id(id) {
 							// special case — /[...rest]/ could contain zero segments
 							const rest_match = /^\[\.\.\.(\w+)(?:=(\w+))?\]$/.exec(segment);
 							if (rest_match) {
-								names.push(rest_match[1]);
-								types.push(rest_match[2]);
-								optional.push(false);
+								params.push({ name: rest_match[1], matcher: rest_match[2], optional: false });
 								return '(?:/(.*))?';
 							}
 							// special case — /[[optional]]/ could contain zero segments
 							const optional_match = /^\[\[(\w+)(?:=(\w+))?\]\]$/.exec(segment);
 							if (optional_match) {
-								names.push(optional_match[1]);
-								types.push(optional_match[2]);
-								optional.push(true);
+								params.push({
+									name: optional_match[1],
+									matcher: optional_match[2],
+									optional: true
+								});
 								return '(?:/([^/]+))?';
 							}
 
@@ -73,14 +67,12 @@ export function parse_route_id(id) {
 											);
 										}
 
-										const [, is_optional, is_rest, name, type] = match;
+										const [, is_optional, is_rest, name, matcher] = match;
 										// It's assumed that the following invalid route id cases are already checked
 										// - unbalanced brackets
 										// - optional param following rest param
 
-										names.push(name);
-										types.push(type);
-										optional.push(!!is_optional);
+										params.push({ name, matcher, optional: !!is_optional });
 										return is_rest ? '(.*?)' : is_optional ? '([^/]*)?' : '([^/]+?)';
 									}
 
@@ -95,7 +87,7 @@ export function parse_route_id(id) {
 						.join('')}${add_trailing_slash ? '/?' : ''}$`
 			  );
 
-	return { pattern, names, types, optional };
+	return { pattern, params };
 }
 
 /**
@@ -119,35 +111,32 @@ export function get_route_segments(route) {
 
 /**
  * @param {RegExpMatchArray} match
- * @param {{
- *   names: string[];
- *   types: string[];
- *   optional: boolean[];
- * }} candidate
+ * @param {Array<{ name: string, matcher: string, optional: boolean }>} params
  * @param {Record<string, import('types').ParamMatcher>} matchers
  */
-export function exec(match, { names, types, optional }, matchers) {
+export function exec(match, params, matchers) {
 	/** @type {Record<string, string>} */
-	const params = {};
+	const result = {};
+
+	console.log(match, params);
 
-	for (let i = 0; i < names.length; i += 1) {
-		const name = names[i];
-		const type = types[i];
+	for (let i = 0; i < params.length; i += 1) {
+		const param = params[i];
 		let value = match[i + 1];
 
-		if (value || !optional[i]) {
-			if (type) {
-				const matcher = matchers[type];
-				if (!matcher) throw new Error(`Missing "${type}" param matcher`); // TODO do this ahead of time?
+		if (value || !param.optional) {
+			if (param.matcher) {
+				const matcher = matchers[param.matcher];
+				if (!matcher) throw new Error(`Missing "${param.matcher}" param matcher`); // TODO do this ahead of time?
 
 				if (!matcher(value)) return;
 			}
 
-			params[name] = value ?? '';
+			result[param.name] = value ?? '';
 		}
 	}
 
-	return params;
+	return result;
 }
 
 /** @param {string} str */
diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index c4b585ac5653..8d69b0971a06 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -5,63 +5,51 @@ import { exec, parse_route_id } from './routing.js';
 const tests = {
 	'/': {
 		pattern: /^\/$/,
-		names: [],
-		types: []
+		params: []
 	},
 	'/blog': {
 		pattern: /^\/blog\/?$/,
-		names: [],
-		types: []
+		params: []
 	},
 	'/blog.json': {
 		pattern: /^\/blog\.json$/,
-		names: [],
-		types: []
+		params: []
 	},
 	'/blog/[slug]': {
 		pattern: /^\/blog\/([^/]+?)\/?$/,
-		names: ['slug'],
-		types: [undefined]
+		params: [{ name: 'slug', matcher: undefined }]
 	},
 	'/blog/[slug].json': {
 		pattern: /^\/blog\/([^/]+?)\.json$/,
-		names: ['slug'],
-		types: [undefined]
+		params: [{ name: 'slug', matcher: undefined }]
 	},
 	'/blog/[[slug]]': {
 		pattern: /^\/blog(?:\/([^/]+))?\/?$/,
-		names: ['slug'],
-		types: [undefined]
+		params: [{ name: 'slug', matcher: undefined }]
 	},
 	'/blog/[[slug=type]]/sub': {
 		pattern: /^\/blog(?:\/([^/]+))?\/sub\/?$/,
-		names: ['slug'],
-		types: ['type']
+		params: [{ name: 'slug', matcher: undefined }]
 	},
 	'/blog/[[slug]].json': {
 		pattern: /^\/blog\/([^/]*)?\.json$/,
-		names: ['slug'],
-		types: [undefined]
+		params: [{ name: 'slug', matcher: undefined }]
 	},
 	'/[...catchall]': {
 		pattern: /^(?:\/(.*))?\/?$/,
-		names: ['catchall'],
-		types: [undefined]
+		params: [{ name: 'catchall', matcher: undefined }]
 	},
 	'/foo/[...catchall]/bar': {
 		pattern: /^\/foo(?:\/(.*))?\/bar\/?$/,
-		names: ['catchall'],
-		types: [undefined]
+		params: [{ name: 'catchall', matcher: undefined }]
 	},
 	'/matched/[id=uuid]': {
 		pattern: /^\/matched\/([^/]+?)\/?$/,
-		names: ['id'],
-		types: ['uuid']
+		params: [{ name: 'id', matcher: undefined }]
 	},
 	'/@-symbol/[id]': {
 		pattern: /^\/@-symbol\/([^/]+?)\/?$/,
-		names: ['id'],
-		types: [undefined]
+		params: [{ name: 'id', matcher: undefined }]
 	}
 };
 
@@ -70,8 +58,7 @@ for (const [key, expected] of Object.entries(tests)) {
 		const actual = parse_route_id(key);
 
 		assert.equal(actual.pattern.toString(), expected.pattern.toString());
-		assert.equal(actual.names, expected.names);
-		assert.equal(actual.types, expected.types);
+		assert.equal(actual.params, expected.params);
 	});
 }
 
@@ -165,17 +152,13 @@ const exec_tests = [
 
 for (const { path, route, expected } of exec_tests) {
 	test(`exec extracts params correctly for ${path} from ${route}`, () => {
-		const { pattern, names, types, optional } = parse_route_id(route);
+		const { pattern, params } = parse_route_id(route);
 		const match = pattern.exec(path);
 		if (!match) throw new Error(`Failed to match ${path}`);
-		const actual = exec(
-			match,
-			{ names, types, optional },
-			{
-				matches: () => true,
-				doesntmatch: () => false
-			}
-		);
+		const actual = exec(match, params, {
+			matches: () => true,
+			doesntmatch: () => false
+		});
 		assert.equal(actual, expected);
 	});
 }
diff --git a/packages/kit/types/internal.d.ts b/packages/kit/types/internal.d.ts
index 33e084bc3315..bf8ee4ca802a 100644
--- a/packages/kit/types/internal.d.ts
+++ b/packages/kit/types/internal.d.ts
@@ -169,9 +169,11 @@ export interface RouteData {
 
 	segment: string;
 	pattern: RegExp;
-	names: string[];
-	types: string[];
-	optional: boolean[];
+	params: Array<{
+		name: string;
+		matcher: string;
+		optional: boolean;
+	}>;
 
 	layout: PageNode | null;
 	error: PageNode | null;
@@ -337,12 +339,8 @@ export type SSREndpoint = Partial<Record<HttpMethod, RequestHandler>> & {
 export interface SSRRoute {
 	id: string;
 	pattern: RegExp;
-	names: string[];
-	types: string[];
-	optional: boolean[];
-
+	params: Array<{ name: string; matcher: string; optional: boolean }>;
 	page: PageNodeIndexes | null;
-
 	endpoint: (() => Promise<SSREndpoint>) | null;
 }
 

From 50c4adcd66763be6a0d4d434c3c7f0aaf8082a54 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 16:53:47 -0500
Subject: [PATCH 03/20] fix

---
 packages/kit/src/utils/routing.js      |  2 --
 packages/kit/src/utils/routing.spec.js | 18 +++++++++---------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index eb119a97b94e..564645c42141 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -118,8 +118,6 @@ export function exec(match, params, matchers) {
 	/** @type {Record<string, string>} */
 	const result = {};
 
-	console.log(match, params);
-
 	for (let i = 0; i < params.length; i += 1) {
 		const param = params[i];
 		let value = match[i + 1];
diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index 8d69b0971a06..5f838f2aace2 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -17,39 +17,39 @@ const tests = {
 	},
 	'/blog/[slug]': {
 		pattern: /^\/blog\/([^/]+?)\/?$/,
-		params: [{ name: 'slug', matcher: undefined }]
+		params: [{ name: 'slug', matcher: undefined, optional: false }]
 	},
 	'/blog/[slug].json': {
 		pattern: /^\/blog\/([^/]+?)\.json$/,
-		params: [{ name: 'slug', matcher: undefined }]
+		params: [{ name: 'slug', matcher: undefined, optional: false }]
 	},
 	'/blog/[[slug]]': {
 		pattern: /^\/blog(?:\/([^/]+))?\/?$/,
-		params: [{ name: 'slug', matcher: undefined }]
+		params: [{ name: 'slug', matcher: undefined, optional: true }]
 	},
 	'/blog/[[slug=type]]/sub': {
 		pattern: /^\/blog(?:\/([^/]+))?\/sub\/?$/,
-		params: [{ name: 'slug', matcher: undefined }]
+		params: [{ name: 'slug', matcher: 'type', optional: true }]
 	},
 	'/blog/[[slug]].json': {
 		pattern: /^\/blog\/([^/]*)?\.json$/,
-		params: [{ name: 'slug', matcher: undefined }]
+		params: [{ name: 'slug', matcher: undefined, optional: true }]
 	},
 	'/[...catchall]': {
 		pattern: /^(?:\/(.*))?\/?$/,
-		params: [{ name: 'catchall', matcher: undefined }]
+		params: [{ name: 'catchall', matcher: undefined, optional: false }]
 	},
 	'/foo/[...catchall]/bar': {
 		pattern: /^\/foo(?:\/(.*))?\/bar\/?$/,
-		params: [{ name: 'catchall', matcher: undefined }]
+		params: [{ name: 'catchall', matcher: undefined, optional: false }]
 	},
 	'/matched/[id=uuid]': {
 		pattern: /^\/matched\/([^/]+?)\/?$/,
-		params: [{ name: 'id', matcher: undefined }]
+		params: [{ name: 'id', matcher: 'uuid', optional: false }]
 	},
 	'/@-symbol/[id]': {
 		pattern: /^\/@-symbol\/([^/]+?)\/?$/,
-		params: [{ name: 'id', matcher: undefined }]
+		params: [{ name: 'id', matcher: undefined, optional: false }]
 	}
 };
 

From e3458a4d1acb7dee760c26d7b807d5ce43c2efeb Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 17:00:36 -0500
Subject: [PATCH 04/20] always add trailing slash, that logic is way out of
 date

---
 packages/kit/src/utils/routing.js | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 564645c42141..7a1ead754d48 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -8,16 +8,12 @@ export function parse_route_id(id) {
 	/** @type {Array<{ name: string, matcher: string, optional: boolean }>} */
 	const params = [];
 
-	// `/foo` should get an optional trailing slash, `/foo.json` should not
-	// const add_trailing_slash = !/\.[a-z]+$/.test(key);
-	let add_trailing_slash = true;
-
 	const pattern =
 		id === '/'
 			? /^\/$/
 			: new RegExp(
 					`^${get_route_segments(id)
-						.map((segment, i, segments) => {
+						.map((segment) => {
 							// special case — /[...rest]/ could contain zero segments
 							const rest_match = /^\[\.\.\.(\w+)(?:=(\w+))?\]$/.exec(segment);
 							if (rest_match) {
@@ -35,8 +31,6 @@ export function parse_route_id(id) {
 								return '(?:/([^/]+))?';
 							}
 
-							const is_last = i === segments.length - 1;
-
 							if (!segment) {
 								return;
 							}
@@ -76,15 +70,13 @@ export function parse_route_id(id) {
 										return is_rest ? '(.*?)' : is_optional ? '([^/]*)?' : '([^/]+?)';
 									}
 
-									if (is_last && content.includes('.')) add_trailing_slash = false;
-
 									return escape(content);
 								})
 								.join('');
 
 							return '/' + result;
 						})
-						.join('')}${add_trailing_slash ? '/?' : ''}$`
+						.join('')}/?$`
 			  );
 
 	return { pattern, params };

From 78ca9bdf91f9148ccbcf956c8438439732c0ff03 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 17:32:52 -0500
Subject: [PATCH 05/20] fix tests

---
 .../src/core/sync/create_manifest_data/index.spec.js | 12 ++++++------
 packages/kit/src/utils/routing.spec.js               |  6 +++---
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/packages/kit/src/core/sync/create_manifest_data/index.spec.js b/packages/kit/src/core/sync/create_manifest_data/index.spec.js
index e036d3f748e1..c386d8ac0614 100644
--- a/packages/kit/src/core/sync/create_manifest_data/index.spec.js
+++ b/packages/kit/src/core/sync/create_manifest_data/index.spec.js
@@ -87,7 +87,7 @@ test('creates routes', () => {
 		},
 		{
 			id: '/blog.json',
-			pattern: '/^/blog.json$/',
+			pattern: '/^/blog.json/?$/',
 			endpoint: { file: 'samples/basic/blog.json/+server.js' }
 		},
 		{
@@ -97,7 +97,7 @@ test('creates routes', () => {
 		},
 		{
 			id: '/blog/[slug].json',
-			pattern: '/^/blog/([^/]+?).json$/',
+			pattern: '/^/blog/([^/]+?).json/?$/',
 			endpoint: {
 				file: 'samples/basic/blog/[slug].json/+server.ts'
 			}
@@ -308,7 +308,7 @@ test('allows rest parameters inside segments', () => {
 		},
 		{
 			id: '/[...rest].json',
-			pattern: '/^/(.*?).json$/',
+			pattern: '/^/(.*?).json/?$/',
 			endpoint: {
 				file: 'samples/rest-prefix-suffix/[...rest].json/+server.js'
 			}
@@ -408,7 +408,7 @@ test('allows multiple slugs', () => {
 	assert.equal(routes.filter((route) => route.endpoint).map(simplify_route), [
 		{
 			id: '/[file].[ext]',
-			pattern: '/^/([^/]+?).([^/]+?)$/',
+			pattern: '/^/([^/]+?).([^/]+?)/?$/',
 			endpoint: {
 				file: 'samples/multiple-slugs/[file].[ext]/+server.js'
 			}
@@ -467,7 +467,7 @@ test('works with custom extensions', () => {
 		},
 		{
 			id: '/blog.json',
-			pattern: '/^/blog.json$/',
+			pattern: '/^/blog.json/?$/',
 			endpoint: {
 				file: 'samples/custom-extension/blog.json/+server.js'
 			}
@@ -479,7 +479,7 @@ test('works with custom extensions', () => {
 		},
 		{
 			id: '/blog/[slug].json',
-			pattern: '/^/blog/([^/]+?).json$/',
+			pattern: '/^/blog/([^/]+?).json/?$/',
 			endpoint: {
 				file: 'samples/custom-extension/blog/[slug].json/+server.js'
 			}
diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index 5f838f2aace2..163c3ad3da6d 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -12,7 +12,7 @@ const tests = {
 		params: []
 	},
 	'/blog.json': {
-		pattern: /^\/blog\.json$/,
+		pattern: /^\/blog\.json\/?$/,
 		params: []
 	},
 	'/blog/[slug]': {
@@ -20,7 +20,7 @@ const tests = {
 		params: [{ name: 'slug', matcher: undefined, optional: false }]
 	},
 	'/blog/[slug].json': {
-		pattern: /^\/blog\/([^/]+?)\.json$/,
+		pattern: /^\/blog\/([^/]+?)\.json\/?$/,
 		params: [{ name: 'slug', matcher: undefined, optional: false }]
 	},
 	'/blog/[[slug]]': {
@@ -32,7 +32,7 @@ const tests = {
 		params: [{ name: 'slug', matcher: 'type', optional: true }]
 	},
 	'/blog/[[slug]].json': {
-		pattern: /^\/blog\/([^/]*)?\.json$/,
+		pattern: /^\/blog\/([^/]*)?\.json\/?$/,
 		params: [{ name: 'slug', matcher: undefined, optional: true }]
 	},
 	'/[...catchall]': {

From ed3045d10231c5272fb41b8f9628e7537c62a4ed Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 17:37:41 -0500
Subject: [PATCH 06/20] DRY out

---
 packages/kit/src/utils/routing.js | 12 +++++++-----
 packages/kit/types/internal.d.ts  | 14 ++++++++------
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 7a1ead754d48..ae8ede07911b 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -5,7 +5,7 @@ const param_pattern = /^(\[)?(\.\.\.)?(\w+)(?:=(\w+))?(\])?$/;
  * @param {string} id
  */
 export function parse_route_id(id) {
-	/** @type {Array<{ name: string, matcher: string, optional: boolean }>} */
+	/** @type {import('types').RouteParam[]} */
 	const params = [];
 
 	const pattern =
@@ -103,16 +103,18 @@ export function get_route_segments(route) {
 
 /**
  * @param {RegExpMatchArray} match
- * @param {Array<{ name: string, matcher: string, optional: boolean }>} params
+ * @param {import('types').RouteParam[]} params
  * @param {Record<string, import('types').ParamMatcher>} matchers
  */
 export function exec(match, params, matchers) {
 	/** @type {Record<string, string>} */
 	const result = {};
 
-	for (let i = 0; i < params.length; i += 1) {
-		const param = params[i];
-		let value = match[i + 1];
+	let p = 0;
+
+	for (let i = 1; i < match.length; i += 1) {
+		const param = params[p++];
+		const value = match[i];
 
 		if (value || !param.optional) {
 			if (param.matcher) {
diff --git a/packages/kit/types/internal.d.ts b/packages/kit/types/internal.d.ts
index bf8ee4ca802a..d543c250312d 100644
--- a/packages/kit/types/internal.d.ts
+++ b/packages/kit/types/internal.d.ts
@@ -158,6 +158,12 @@ export interface Respond {
 	(request: Request, options: SSROptions, state: SSRState): Promise<Response>;
 }
 
+export interface RouteParam {
+	name: string;
+	matcher: string;
+	optional: boolean;
+}
+
 /**
  * Represents a route segment in the app. It can either be an intermediate node
  * with only layout/error pages, or a leaf, at which point either `page` and `leaf`
@@ -169,11 +175,7 @@ export interface RouteData {
 
 	segment: string;
 	pattern: RegExp;
-	params: Array<{
-		name: string;
-		matcher: string;
-		optional: boolean;
-	}>;
+	params: RouteParam[];
 
 	layout: PageNode | null;
 	error: PageNode | null;
@@ -339,7 +341,7 @@ export type SSREndpoint = Partial<Record<HttpMethod, RequestHandler>> & {
 export interface SSRRoute {
 	id: string;
 	pattern: RegExp;
-	params: Array<{ name: string; matcher: string; optional: boolean }>;
+	params: RouteParam[];
 	page: PageNodeIndexes | null;
 	endpoint: (() => Promise<SSREndpoint>) | null;
 }

From 31b05a4f796b3ca3f68486f0876743e72fe02ab3 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 17:42:20 -0500
Subject: [PATCH 07/20] track more param info

---
 packages/kit/src/utils/routing.js | 20 +++++++++++++++++---
 packages/kit/types/internal.d.ts  |  2 ++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index ae8ede07911b..3de8eaf1c56b 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -17,7 +17,13 @@ export function parse_route_id(id) {
 							// special case — /[...rest]/ could contain zero segments
 							const rest_match = /^\[\.\.\.(\w+)(?:=(\w+))?\]$/.exec(segment);
 							if (rest_match) {
-								params.push({ name: rest_match[1], matcher: rest_match[2], optional: false });
+								params.push({
+									name: rest_match[1],
+									matcher: rest_match[2],
+									optional: false,
+									rest: true,
+									standalone: true
+								});
 								return '(?:/(.*))?';
 							}
 							// special case — /[[optional]]/ could contain zero segments
@@ -26,7 +32,9 @@ export function parse_route_id(id) {
 								params.push({
 									name: optional_match[1],
 									matcher: optional_match[2],
-									optional: true
+									optional: true,
+									rest: false,
+									standalone: true
 								});
 								return '(?:/([^/]+))?';
 							}
@@ -66,7 +74,13 @@ export function parse_route_id(id) {
 										// - unbalanced brackets
 										// - optional param following rest param
 
-										params.push({ name, matcher, optional: !!is_optional });
+										params.push({
+											name,
+											matcher,
+											optional: !!is_optional,
+											rest: !!is_rest,
+											standalone: false
+										});
 										return is_rest ? '(.*?)' : is_optional ? '([^/]*)?' : '([^/]+?)';
 									}
 
diff --git a/packages/kit/types/internal.d.ts b/packages/kit/types/internal.d.ts
index d543c250312d..769a6e56a2ab 100644
--- a/packages/kit/types/internal.d.ts
+++ b/packages/kit/types/internal.d.ts
@@ -162,6 +162,8 @@ export interface RouteParam {
 	name: string;
 	matcher: string;
 	optional: boolean;
+	rest: boolean;
+	standalone: boolean;
 }
 
 /**

From 886303e76fa0814c45d88be8563e7cf78c46ffb5 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 19:26:28 -0500
Subject: [PATCH 08/20] check for missing matcher at manifest creation time

---
 packages/kit/src/core/sync/create_manifest_data/index.js | 8 ++++++++
 packages/kit/src/utils/routing.js                        | 2 --
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/packages/kit/src/core/sync/create_manifest_data/index.js b/packages/kit/src/core/sync/create_manifest_data/index.js
index 96f5ff503d84..4fc738f92ea3 100644
--- a/packages/kit/src/core/sync/create_manifest_data/index.js
+++ b/packages/kit/src/core/sync/create_manifest_data/index.js
@@ -24,6 +24,14 @@ export default function create_manifest_data({
 	const matchers = create_matchers(config, cwd);
 	const { nodes, routes } = create_routes_and_nodes(cwd, config, fallback);
 
+	for (const route of routes) {
+		for (const param of route.params) {
+			if (param.matcher && !matchers[param.matcher]) {
+				throw new Error(`No matcher found for parameter '${param.matcher}' in route ${route.id}`);
+			}
+		}
+	}
+
 	return {
 		assets,
 		matchers,
diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 3de8eaf1c56b..d4a65740b972 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -133,8 +133,6 @@ export function exec(match, params, matchers) {
 		if (value || !param.optional) {
 			if (param.matcher) {
 				const matcher = matchers[param.matcher];
-				if (!matcher) throw new Error(`Missing "${param.matcher}" param matcher`); // TODO do this ahead of time?
-
 				if (!matcher(value)) return;
 			}
 

From d149a3855ecd8cdd4760e2e1703671f24d1c5d2a Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 22:39:52 -0500
Subject: [PATCH 09/20] working, i think

---
 packages/kit/src/utils/routing.js | 40 +++++++++++++++++++++----------
 packages/kit/types/internal.d.ts  |  2 +-
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index d4a65740b972..0ff76eea5afd 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -22,7 +22,7 @@ export function parse_route_id(id) {
 									matcher: rest_match[2],
 									optional: false,
 									rest: true,
-									standalone: true
+									chained: true
 								});
 								return '(?:/(.*))?';
 							}
@@ -34,7 +34,7 @@ export function parse_route_id(id) {
 									matcher: optional_match[2],
 									optional: true,
 									rest: false,
-									standalone: true
+									chained: true
 								});
 								return '(?:/([^/]+))?';
 							}
@@ -79,7 +79,7 @@ export function parse_route_id(id) {
 											matcher,
 											optional: !!is_optional,
 											rest: !!is_rest,
-											standalone: false
+											chained: is_rest ? i === 1 && parts[0] === '' : false
 										});
 										return is_rest ? '(.*?)' : is_optional ? '([^/]*)?' : '([^/]+?)';
 									}
@@ -124,20 +124,34 @@ export function exec(match, params, matchers) {
 	/** @type {Record<string, string>} */
 	const result = {};
 
-	let p = 0;
+	let m = 1;
+	let prev = '';
 
-	for (let i = 1; i < match.length; i += 1) {
-		const param = params[p++];
-		const value = match[i];
+	for (const param of params) {
+		let value = (param.chained && prev) || match[m++];
 
-		if (value || !param.optional) {
-			if (param.matcher) {
-				const matcher = matchers[param.matcher];
-				if (!matcher(value)) return;
-			}
+		if (param.rest && param.chained && prev && match[m]) {
+			value += `/${match[m++]}`;
+		}
+
+		if (!value) {
+			if (param.rest) result[param.name] = '';
+			continue;
+		}
 
-			result[param.name] = value ?? '';
+		if (param.matcher) {
+			const matcher = matchers[param.matcher];
+			if (!matcher(value)) {
+				if (param.optional && param.chained) {
+					prev = value;
+					continue;
+				}
+				return;
+			}
 		}
+
+		result[param.name] = value;
+		prev = '';
 	}
 
 	return result;
diff --git a/packages/kit/types/internal.d.ts b/packages/kit/types/internal.d.ts
index 769a6e56a2ab..a2ae2f371283 100644
--- a/packages/kit/types/internal.d.ts
+++ b/packages/kit/types/internal.d.ts
@@ -163,7 +163,7 @@ export interface RouteParam {
 	matcher: string;
 	optional: boolean;
 	rest: boolean;
-	standalone: boolean;
+	chained: boolean;
 }
 
 /**

From 6cd925d78fc33b08809fafb03c64aaf9b81dd3f0 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 22:42:55 -0500
Subject: [PATCH 10/20] shuffle around

---
 packages/kit/src/utils/routing.js | 34 +++++++++++++++----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 0ff76eea5afd..c92be7fa9695 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -125,33 +125,33 @@ export function exec(match, params, matchers) {
 	const result = {};
 
 	let m = 1;
-	let prev = '';
+	let buffered = '';
 
 	for (const param of params) {
-		let value = (param.chained && prev) || match[m++];
+		let value = (param.chained && buffered) || match[m++];
 
-		if (param.rest && param.chained && prev && match[m]) {
+		if (param.rest && param.chained && buffered && match[m]) {
 			value += `/${match[m++]}`;
 		}
 
-		if (!value) {
-			if (param.rest) result[param.name] = '';
-			continue;
-		}
-
-		if (param.matcher) {
-			const matcher = matchers[param.matcher];
-			if (!matcher(value)) {
-				if (param.optional && param.chained) {
-					prev = value;
-					continue;
+		if (value) {
+			if (param.matcher) {
+				const matcher = matchers[param.matcher];
+				if (!matcher(value)) {
+					if (param.optional && param.chained) {
+						buffered = value;
+						continue;
+					}
+					return;
 				}
-				return;
 			}
+
+			result[param.name] = value;
+		} else {
+			if (param.rest) result[param.name] = '';
 		}
 
-		result[param.name] = value;
-		prev = '';
+		buffered = '';
 	}
 
 	return result;

From e5405a7bed53d9fba17a77d298d95cc8cd5ce25c Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 23:53:54 -0500
Subject: [PATCH 11/20] ok try this

---
 packages/kit/src/utils/routing.js | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index c92be7fa9695..706324bd9ac0 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -124,14 +124,19 @@ export function exec(match, params, matchers) {
 	/** @type {Record<string, string>} */
 	const result = {};
 
-	let m = 1;
+	const values = match.slice(1);
+
+	let p = 0;
+	let v = 0;
+
 	let buffered = '';
 
-	for (const param of params) {
-		let value = (param.chained && buffered) || match[m++];
+	while (p < params.length) {
+		const param = params[p++];
+		let value = values[v++];
 
-		if (param.rest && param.chained && buffered && match[m]) {
-			value += `/${match[m++]}`;
+		if (param.chained && param.rest && buffered) {
+			value = value ? buffered + '/' + value : buffered;
 		}
 
 		if (value) {
@@ -139,7 +144,17 @@ export function exec(match, params, matchers) {
 				const matcher = matchers[param.matcher];
 				if (!matcher(value)) {
 					if (param.optional && param.chained) {
-						buffered = value;
+						let i = values.indexOf(undefined, v);
+
+						if (i === -1) {
+							buffered = value;
+						}
+
+						while (i >= v) {
+							values[i] = values[i - 1];
+							i -= 1;
+						}
+
 						continue;
 					}
 					return;

From 64911dc1d0290c8ac1c0cb14eea541c8a975600c Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 21 Nov 2022 23:58:54 -0500
Subject: [PATCH 12/20] update tests

---
 packages/kit/src/utils/routing.spec.js | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index 163c3ad3da6d..27b6310a0330 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -17,39 +17,39 @@ const tests = {
 	},
 	'/blog/[slug]': {
 		pattern: /^\/blog\/([^/]+?)\/?$/,
-		params: [{ name: 'slug', matcher: undefined, optional: false }]
+		params: [{ name: 'slug', matcher: undefined, optional: false, rest: false, chained: false }]
 	},
 	'/blog/[slug].json': {
 		pattern: /^\/blog\/([^/]+?)\.json\/?$/,
-		params: [{ name: 'slug', matcher: undefined, optional: false }]
+		params: [{ name: 'slug', matcher: undefined, optional: false, rest: false, chained: false }]
 	},
 	'/blog/[[slug]]': {
 		pattern: /^\/blog(?:\/([^/]+))?\/?$/,
-		params: [{ name: 'slug', matcher: undefined, optional: true }]
+		params: [{ name: 'slug', matcher: undefined, optional: true, rest: false, chained: true }]
 	},
 	'/blog/[[slug=type]]/sub': {
 		pattern: /^\/blog(?:\/([^/]+))?\/sub\/?$/,
-		params: [{ name: 'slug', matcher: 'type', optional: true }]
+		params: [{ name: 'slug', matcher: 'type', optional: true, rest: false, chained: true }]
 	},
 	'/blog/[[slug]].json': {
 		pattern: /^\/blog\/([^/]*)?\.json\/?$/,
-		params: [{ name: 'slug', matcher: undefined, optional: true }]
+		params: [{ name: 'slug', matcher: undefined, optional: true, rest: false, chained: false }]
 	},
 	'/[...catchall]': {
 		pattern: /^(?:\/(.*))?\/?$/,
-		params: [{ name: 'catchall', matcher: undefined, optional: false }]
+		params: [{ name: 'catchall', matcher: undefined, optional: false, rest: true, chained: true }]
 	},
 	'/foo/[...catchall]/bar': {
 		pattern: /^\/foo(?:\/(.*))?\/bar\/?$/,
-		params: [{ name: 'catchall', matcher: undefined, optional: false }]
+		params: [{ name: 'catchall', matcher: undefined, optional: false, rest: true, chained: true }]
 	},
 	'/matched/[id=uuid]': {
 		pattern: /^\/matched\/([^/]+?)\/?$/,
-		params: [{ name: 'id', matcher: 'uuid', optional: false }]
+		params: [{ name: 'id', matcher: 'uuid', optional: false, rest: false, chained: false }]
 	},
 	'/@-symbol/[id]': {
 		pattern: /^\/@-symbol\/([^/]+?)\/?$/,
-		params: [{ name: 'id', matcher: undefined, optional: false }]
+		params: [{ name: 'id', matcher: undefined, optional: false, rest: false, chained: false }]
 	}
 };
 

From 33ccb66bb29d2effc8f3fcd402fd645172d1bcab Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 00:03:27 -0500
Subject: [PATCH 13/20] fix tests

---
 packages/kit/src/utils/routing.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 706324bd9ac0..7761105714b4 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -139,7 +139,9 @@ export function exec(match, params, matchers) {
 			value = value ? buffered + '/' + value : buffered;
 		}
 
-		if (value) {
+		if (value === undefined) {
+			if (param.rest) result[param.name] = '';
+		} else {
 			if (param.matcher) {
 				const matcher = matchers[param.matcher];
 				if (!matcher(value)) {
@@ -162,13 +164,12 @@ export function exec(match, params, matchers) {
 			}
 
 			result[param.name] = value;
-		} else {
-			if (param.rest) result[param.name] = '';
 		}
 
 		buffered = '';
 	}
 
+	if (buffered) return;
 	return result;
 }
 

From 4d3e6c7acd014aba3023f0d52a57ec604e5e5c08 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 00:17:06 -0500
Subject: [PATCH 14/20] lint

---
 packages/kit/src/utils/routing.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 7761105714b4..1ccb8117b076 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -146,6 +146,7 @@ export function exec(match, params, matchers) {
 				const matcher = matchers[param.matcher];
 				if (!matcher(value)) {
 					if (param.optional && param.chained) {
+						// @ts-expect-error TypeScript is... wrong
 						let i = values.indexOf(undefined, v);
 
 						if (i === -1) {

From caa1ca3717c75210a1fed39c252ace50dc48948f Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 00:20:23 -0500
Subject: [PATCH 15/20] fix

---
 sites/kit.svelte.dev/src/lib/docs/server/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sites/kit.svelte.dev/src/lib/docs/server/index.js b/sites/kit.svelte.dev/src/lib/docs/server/index.js
index 878c2be6be21..c7465541da4f 100644
--- a/sites/kit.svelte.dev/src/lib/docs/server/index.js
+++ b/sites/kit.svelte.dev/src/lib/docs/server/index.js
@@ -124,7 +124,7 @@ export async function read_file(file) {
 					}
 					if (source.includes('./$types') && !source.includes('@filename: $types.d.ts')) {
 						const params = parse_route_id(options.file || `+page.${language}`)
-							.names.map((name) => `${name}: string`)
+							.params.map((param) => `${param.name}: string`)
 							.join(', ');
 
 						injected.push(

From 6e3c7df678d02a2f0fb62d0e74b62f19ee3b3c8e Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 00:21:33 -0500
Subject: [PATCH 16/20] changeset

---
 .changeset/forty-icons-switch.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/forty-icons-switch.md

diff --git a/.changeset/forty-icons-switch.md b/.changeset/forty-icons-switch.md
new file mode 100644
index 000000000000..42fc680358d9
--- /dev/null
+++ b/.changeset/forty-icons-switch.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Allow chained optional parameters

From 2cbf6043f81f2808a66901c17174c3a4ac72e4ac Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 10:07:34 -0500
Subject: [PATCH 17/20] unit tests

---
 packages/kit/src/utils/routing.spec.js               | 10 ++++++++++
 .../routes/routing/optional-then-rest/+layout.svelte |  4 ----
 .../routes/routing/optional-then-rest/+page.svelte   |  0
 .../[[x=numeric]]/[...y]/+page.svelte                |  6 ------
 packages/kit/test/apps/basics/test/test.js           | 12 ------------
 5 files changed, 10 insertions(+), 22 deletions(-)
 delete mode 100644 packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte
 delete mode 100644 packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+page.svelte
 delete mode 100644 packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte

diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index 27b6310a0330..d069e690da13 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -147,6 +147,16 @@ const exec_tests = [
 		route: '/[...slug1=doesntmatch]',
 		path: '/',
 		expected: undefined
+	},
+	{
+		route: '/[[slug=doesntmatch]]/[...rest]',
+		path: '/foo',
+		expected: { rest: 'foo' }
+	},
+	{
+		route: '/[[slug1=doesntmatch]]/[[slug2=matches]]/[[slug3=doesntmatch]]/[...rest].json',
+		path: '/foo/bar/baz.json',
+		expected: { slug2: 'foo', rest: 'bar/baz' }
 	}
 ];
 
diff --git a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte
deleted file mode 100644
index 023662db9505..000000000000
--- a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+layout.svelte
+++ /dev/null
@@ -1,4 +0,0 @@
-<a href="/routing/optional-then-rest/a/1">/routing/optional-then-rest/a/1</a>
-<a href="/routing/optional-then-rest/1/2">/routing/optional-then-rest/1/2</a>
-
-<slot />
diff --git a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+page.svelte b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/+page.svelte
deleted file mode 100644
index e69de29bb2d1..000000000000
diff --git a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte b/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte
deleted file mode 100644
index 3ceb365c4a89..000000000000
--- a/packages/kit/test/apps/basics/src/routes/routing/optional-then-rest/[[x=numeric]]/[...y]/+page.svelte
+++ /dev/null
@@ -1,6 +0,0 @@
-<script>
-	import { page } from '$app/stores';
-</script>
-
-<p data-testid="x">{$page.params.x}</p>
-<p data-testid="y">{$page.params.y}</p>
diff --git a/packages/kit/test/apps/basics/test/test.js b/packages/kit/test/apps/basics/test/test.js
index 2c65e444b476..be47fcb68a93 100644
--- a/packages/kit/test/apps/basics/test/test.js
+++ b/packages/kit/test/apps/basics/test/test.js
@@ -1686,18 +1686,6 @@ test.describe('Routing', () => {
 		expect(await page.textContent('p')).toBe('This is your custom error page saying: "Not Found"');
 	});
 
-	test('allows optional parameter before a rest parameter', async ({ page, clicknav }) => {
-		await page.goto('/routing/optional-then-rest');
-
-		await clicknav('[href="/routing/optional-then-rest/a/1"]');
-		expect(await page.textContent('[data-testid="x"]')).toBe('undefined');
-		expect(await page.textContent('[data-testid="y"]')).toBe('a/1');
-
-		await clicknav('[href="/routing/optional-then-rest/1/2"]');
-		expect(await page.textContent('[data-testid="x"]')).toBe('1');
-		expect(await page.textContent('[data-testid="y"]')).toBe('2');
-	});
-
 	if (process.platform !== 'win32') {
 		test('Respects symlinks', async ({ page, clicknav }) => {
 			await page.goto('/routing');

From d3c3959d418a9724c2a01cf974489564466e743b Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 10:17:48 -0500
Subject: [PATCH 18/20] make the code a bit more comprehensible

---
 packages/kit/src/utils/routing.js | 56 +++++++++++++++++--------------
 1 file changed, 30 insertions(+), 26 deletions(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 1ccb8117b076..30610e068b27 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -126,48 +126,52 @@ export function exec(match, params, matchers) {
 
 	const values = match.slice(1);
 
-	let p = 0;
-	let v = 0;
-
 	let buffered = '';
 
-	while (p < params.length) {
-		const param = params[p++];
-		let value = values[v++];
+	for (let i = 0; i < params.length; i += 1) {
+		const param = params[i];
+		let value = values[i];
 
 		if (param.chained && param.rest && buffered) {
+			// in the `[[lang=lang]]/[...rest]` case, if `lang` didn't
+			// match, we roll it over into the rest value
 			value = value ? buffered + '/' + value : buffered;
 		}
 
+		buffered = '';
+
 		if (value === undefined) {
+			// if `value` is undefined, it means this is
+			// an optional or rest parameter
 			if (param.rest) result[param.name] = '';
 		} else {
-			if (param.matcher) {
-				const matcher = matchers[param.matcher];
-				if (!matcher(value)) {
-					if (param.optional && param.chained) {
-						// @ts-expect-error TypeScript is... wrong
-						let i = values.indexOf(undefined, v);
-
-						if (i === -1) {
-							buffered = value;
-						}
-
-						while (i >= v) {
-							values[i] = values[i - 1];
-							i -= 1;
-						}
-
-						continue;
+			if (param.matcher && !matchers[param.matcher](value)) {
+				// in the `/[[a=b]]/[[c=d]]` case, if the value didn't satisfy the `b` matcher,
+				// try again with the next segment by shifting values rightwards
+				if (param.optional && param.chained) {
+					// @ts-expect-error TypeScript is... wrong
+					let j = values.indexOf(undefined, i);
+
+					if (j === -1) {
+						// we can't shift values any further, so hang on to this value
+						// so it can be rolled into a subsequent `[...rest]` param
+						buffered = value;
+					}
+
+					while (j >= i) {
+						values[j] = values[j - 1];
+						j -= 1;
 					}
-					return;
+
+					continue;
 				}
+
+				// otherwise, if the matcher returns `false`, the route did not match
+				return;
 			}
 
 			result[param.name] = value;
 		}
-
-		buffered = '';
 	}
 
 	if (buffered) return;

From eceb4d18b95f1017bf800994b7529b91d049536e Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Tue, 22 Nov 2022 10:18:51 -0500
Subject: [PATCH 19/20] Update .changeset/forty-icons-switch.md

---
 .changeset/forty-icons-switch.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changeset/forty-icons-switch.md b/.changeset/forty-icons-switch.md
index 42fc680358d9..51ef8c4659fa 100644
--- a/.changeset/forty-icons-switch.md
+++ b/.changeset/forty-icons-switch.md
@@ -2,4 +2,4 @@
 '@sveltejs/kit': patch
 ---
 
-Allow chained optional parameters
+Roll over non-matching optional parameters instead of 404ing

From 7c91626705c8a4d644b0fd2bdcd787451874e6d6 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 22 Nov 2022 14:07:12 -0500
Subject: [PATCH 20/20] fix another case

---
 packages/kit/src/utils/routing.js      | 7 ++++++-
 packages/kit/src/utils/routing.spec.js | 5 +++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 30610e068b27..6c71be0ef343 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -155,7 +155,12 @@ export function exec(match, params, matchers) {
 					if (j === -1) {
 						// we can't shift values any further, so hang on to this value
 						// so it can be rolled into a subsequent `[...rest]` param
-						buffered = value;
+						const next = params[i + 1];
+						if (next?.rest && next.chained) {
+							buffered = value;
+						} else {
+							return;
+						}
 					}
 
 					while (j >= i) {
diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index d069e690da13..18d144ce3c7c 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -157,6 +157,11 @@ const exec_tests = [
 		route: '/[[slug1=doesntmatch]]/[[slug2=matches]]/[[slug3=doesntmatch]]/[...rest].json',
 		path: '/foo/bar/baz.json',
 		expected: { slug2: 'foo', rest: 'bar/baz' }
+	},
+	{
+		route: '/[[a=doesntmatch]]/[[b=matches]]/c',
+		path: '/a/b/c',
+		expected: undefined
 	}
 ];