From 900d483cec46e502f1fbf2b3852b27031ea252c6 Mon Sep 17 00:00:00 2001
From: Ben McCann <322311+benmccann@users.noreply.github.com>
Date: Thu, 29 Jun 2023 12:52:56 -0700
Subject: [PATCH 1/2] perf: only have Vite generate relative paths when
 required

---
 .changeset/violet-dryers-nail.md       | 5 +++++
 packages/kit/src/exports/vite/index.js | 8 +++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/violet-dryers-nail.md

diff --git a/.changeset/violet-dryers-nail.md b/.changeset/violet-dryers-nail.md
new file mode 100644
index 000000000000..bb47025bb992
--- /dev/null
+++ b/.changeset/violet-dryers-nail.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+perf: only have Vite generate relative paths when required
diff --git a/packages/kit/src/exports/vite/index.js b/packages/kit/src/exports/vite/index.js
index a26ca5ba3805..3d54214ec3bb 100644
--- a/packages/kit/src/exports/vite/index.js
+++ b/packages/kit/src/exports/vite/index.js
@@ -541,8 +541,14 @@ function kit({ svelte_config }) {
 				// see the kit.output.preloadStrategy option for details on why we have multiple options here
 				const ext = kit.output.preloadStrategy === 'preload-mjs' ? 'mjs' : 'js';
 
+				// We could always use a relative asset base path here, but it's better for performance not to.
+				// E.g. Vite generates `new URL('/asset.png', import.meta).href` for a relative path vs just '/asset.png'.
+				// That's larger and takes longer to run and also causes an HTML diff between SSR and client
+				// causing us to do a more expensive hydration check.
+				const client_base = kit.paths.relative || kit.paths.assets ? './' : kit.paths.base;
+
 				new_config = {
-					base: ssr ? assets_base(kit) : './',
+					base: ssr ? assets_base(kit) : client_base,
 					build: {
 						copyPublicDir: !ssr,
 						cssCodeSplit: true,

From 2525a0e91cb19dc03d6bc0b6b0d45559d786b951 Mon Sep 17 00:00:00 2001
From: Ben McCann <322311+benmccann@users.noreply.github.com>
Date: Wed, 5 Jul 2023 12:54:51 -0700
Subject: [PATCH 2/2] fix for empty base path

---
 packages/kit/src/exports/vite/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kit/src/exports/vite/index.js b/packages/kit/src/exports/vite/index.js
index 3d54214ec3bb..bd5bb27f61db 100644
--- a/packages/kit/src/exports/vite/index.js
+++ b/packages/kit/src/exports/vite/index.js
@@ -545,7 +545,7 @@ function kit({ svelte_config }) {
 				// E.g. Vite generates `new URL('/asset.png', import.meta).href` for a relative path vs just '/asset.png'.
 				// That's larger and takes longer to run and also causes an HTML diff between SSR and client
 				// causing us to do a more expensive hydration check.
-				const client_base = kit.paths.relative || kit.paths.assets ? './' : kit.paths.base;
+				const client_base = kit.paths.relative || kit.paths.assets ? './' : kit.paths.base || '/';
 
 				new_config = {
 					base: ssr ? assets_base(kit) : client_base,