fix: handle srcset attributes with newline after comma (#9388)

fixes #9369

.changeset/late-berries-glow.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: handle srcset attributes with newline after comma

packages/kit/src/core/postbuild/crawl.js

@@ -179,12 +179,15 @@ export function crawl(html, base) {
 								let insideURL = true;
 								value = value.trim();
 								for (let i = 0; i < value.length; i++) {
-									if (value[i] === ',' && (!insideURL || (insideURL && value[i + 1] === ' '))) {
+									if (
+										value[i] === ',' &&
+										(!insideURL || (insideURL && WHITESPACE.test(value[i + 1])))
+									) {
 										candidates.push(value.slice(0, i));
 										value = value.substring(i + 1).trim();
 										i = 0;
 										insideURL = true;
-									} else if (value[i] === ' ') {
+									} else if (WHITESPACE.test(value[i])) {
 										insideURL = false;
 									}
 								}

packages/kit/src/core/postbuild/fixtures/basic-srcset/input.html

@@ -7,5 +7,11 @@
 			src="header.png"
 			srcset="https://example.com/w_200,q_100/header.png 200w, header640.png 640w, header960.png 960w, header1024.png 1024w, header.png"
 		/>
+		<img
+			alt="Troublesome srcset"
+			src="issue-9369.png"
+			srcset="/issue-9369_newline-after-comma-is-bad.png,
+							/issue-9369_800px.png 800,"
+		/>
 	</body>
 </html>

packages/kit/src/core/postbuild/fixtures/basic-srcset/output.json

@@ -5,7 +5,10 @@
 		"/header640.png",
 		"/header960.png",
 		"/header1024.png",
-		"/header.png"
+		"/header.png",
+		"/issue-9369.png",
+		"/issue-9369_newline-after-comma-is-bad.png",
+		"/issue-9369_800px.png"
 	],
 	"ids": []
 }