From b433f3cd878814d6d141be359e5dafa9959b5f9e Mon Sep 17 00:00:00 2001
From: Bao Nguyen <39545125+giaBaoJS@users.noreply.github.com>
Date: Tue, 25 Aug 2026 19:22:56 +0700
Subject: [PATCH] fix: preserve line feed character references in attribute
values (#18691)
Fixes #15555
Pass on whether we're in an attribute to not replace the charcode with the whitespace charcode in that case
---
.changeset/tricky-donkeys-clap.md | 5 ++
.../src/compiler/phases/1-parse/utils/html.js | 15 ++++--
.../convert-entities-line-feed/input.svelte | 1 +
.../convert-entities-line-feed/output.json | 53 +++++++++++++++++++
.../html-entity-line-feed/Component.svelte | 5 ++
.../samples/html-entity-line-feed/_config.js | 15 ++++++
.../samples/html-entity-line-feed/main.svelte | 9 ++++
7 files changed, 98 insertions(+), 5 deletions(-)
create mode 100644 .changeset/tricky-donkeys-clap.md
create mode 100644 packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/input.svelte
create mode 100644 packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/output.json
create mode 100644 packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/Component.svelte
create mode 100644 packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/_config.js
create mode 100644 packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/main.svelte
diff --git a/.changeset/tricky-donkeys-clap.md b/.changeset/tricky-donkeys-clap.md
new file mode 100644
index 0000000000..b363b4ff57
--- /dev/null
+++ b/.changeset/tricky-donkeys-clap.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: preserve line feed character references in attribute values
diff --git a/packages/svelte/src/compiler/phases/1-parse/utils/html.js b/packages/svelte/src/compiler/phases/1-parse/utils/html.js
index 1d660298c7..ccb2005054 100644
--- a/packages/svelte/src/compiler/phases/1-parse/utils/html.js
+++ b/packages/svelte/src/compiler/phases/1-parse/utils/html.js
@@ -60,7 +60,7 @@ export function decode_character_references(html, is_attribute_value) {
return match;
}
- return String.fromCodePoint(validate_code(code));
+ return String.fromCodePoint(validate_code(code, is_attribute_value));
}
);
}
@@ -75,10 +75,15 @@ const NUL = 0;
// Also see: https://en.wikipedia.org/wiki/Plane_(Unicode)
// Also see: https://html.spec.whatwg.org/multipage/parsing.html#preprocessing-the-input-stream
-/** @param {number} code */
-function validate_code(code) {
- // line feed becomes generic whitespace
- if (code === 10) {
+/**
+ * @param {number} code
+ * @param {boolean} is_attribute_value
+ */
+function validate_code(code, is_attribute_value) {
+ // line feed becomes generic whitespace, since it is collapsed along with the
+ // surrounding whitespace anyway. In an attribute value it is significant, so it
+ // is left alone there
+ if (code === 10 && !is_attribute_value) {
return 32;
}
diff --git a/packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/input.svelte b/packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/input.svelte
new file mode 100644
index 0000000000..3ce2c605d6
--- /dev/null
+++ b/packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/input.svelte
@@ -0,0 +1 @@
+A
B
diff --git a/packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/output.json b/packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/output.json
new file mode 100644
index 0000000000..5d1127ccdc
--- /dev/null
+++ b/packages/svelte/tests/parser-legacy/samples/convert-entities-line-feed/output.json
@@ -0,0 +1,53 @@
+{
+ "html": {
+ "type": "Fragment",
+ "start": 0,
+ "end": 32,
+ "children": [
+ {
+ "type": "Element",
+ "start": 0,
+ "end": 32,
+ "name": "p",
+ "attributes": [
+ {
+ "type": "Attribute",
+ "start": 3,
+ "end": 19,
+ "name": "title",
+ "name_loc": {
+ "start": {
+ "line": 1,
+ "column": 3,
+ "character": 3
+ },
+ "end": {
+ "line": 1,
+ "column": 8,
+ "character": 8
+ }
+ },
+ "value": [
+ {
+ "start": 10,
+ "end": 18,
+ "type": "Text",
+ "raw": "A
B",
+ "data": "A\nB"
+ }
+ ]
+ }
+ ],
+ "children": [
+ {
+ "type": "Text",
+ "start": 20,
+ "end": 28,
+ "raw": "A
B",
+ "data": "A B"
+ }
+ ]
+ }
+ ]
+ }
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/Component.svelte b/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/Component.svelte
new file mode 100644
index 0000000000..85b608c739
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/Component.svelte
@@ -0,0 +1,5 @@
+
+
+{text}
diff --git a/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/_config.js b/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/_config.js
new file mode 100644
index 0000000000..f6befd7703
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/_config.js
@@ -0,0 +1,15 @@
+import { test } from '../../test';
+
+export default test({
+ async test({ assert, target }) {
+ // a line feed entity in an attribute value stays a line feed...
+ assert.equal(target.querySelector('#attr')?.getAttribute('title'), 'A\nB');
+ assert.equal(target.querySelector('#attr-decimal')?.getAttribute('title'), 'A\nB');
+
+ // ...including when the attribute is a prop passed to a component
+ assert.equal(target.querySelector('#prop')?.textContent, 'A\nB');
+
+ // other entities in attribute values still decode
+ assert.equal(target.querySelector('#attr-other-entity')?.getAttribute('title'), '©');
+ }
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/main.svelte b/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/main.svelte
new file mode 100644
index 0000000000..d7f5684351
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/html-entity-line-feed/main.svelte
@@ -0,0 +1,9 @@
+
+
+
+
+
+
+