From 42ffe258c58a8bc8e5a41facaa339f8072f3339e Mon Sep 17 00:00:00 2001
From: paoloricciuti <ricciutipaolo@gmail.com>
Date: Mon, 24 Feb 2025 23:43:39 +0100
Subject: [PATCH] fix: allow double hyphen css selector names

---
 .changeset/fast-pants-decide.md                            | 5 +++++
 packages/svelte/src/compiler/phases/1-parse/read/style.js  | 4 ++--
 .../svelte/tests/css/samples/double-hyphen/expected.css    | 4 ++++
 .../svelte/tests/css/samples/double-hyphen/input.svelte    | 7 +++++++
 4 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/fast-pants-decide.md
 create mode 100644 packages/svelte/tests/css/samples/double-hyphen/expected.css
 create mode 100644 packages/svelte/tests/css/samples/double-hyphen/input.svelte

diff --git a/.changeset/fast-pants-decide.md b/.changeset/fast-pants-decide.md
new file mode 100644
index 000000000000..396b80c0e049
--- /dev/null
+++ b/.changeset/fast-pants-decide.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: allow double hyphen css selector names
diff --git a/packages/svelte/src/compiler/phases/1-parse/read/style.js b/packages/svelte/src/compiler/phases/1-parse/read/style.js
index 29e8a0e54143..f8c39f1b1dd1 100644
--- a/packages/svelte/src/compiler/phases/1-parse/read/style.js
+++ b/packages/svelte/src/compiler/phases/1-parse/read/style.js
@@ -566,7 +566,7 @@ function read_attribute_value(parser) {
 }
 
 /**
- * https://www.w3.org/TR/CSS21/syndata.html#value-def-identifier
+ * https://www.w3.org/TR/css-syntax-3/#ident-token-diagram
  * @param {Parser} parser
  */
 function read_identifier(parser) {
@@ -574,7 +574,7 @@ function read_identifier(parser) {
 
 	let identifier = '';
 
-	if (parser.match('--') || parser.match_regex(REGEX_LEADING_HYPHEN_OR_DIGIT)) {
+	if (parser.match_regex(REGEX_LEADING_HYPHEN_OR_DIGIT)) {
 		e.css_expected_identifier(start);
 	}
 
diff --git a/packages/svelte/tests/css/samples/double-hyphen/expected.css b/packages/svelte/tests/css/samples/double-hyphen/expected.css
new file mode 100644
index 000000000000..ab4921b657ea
--- /dev/null
+++ b/packages/svelte/tests/css/samples/double-hyphen/expected.css
@@ -0,0 +1,4 @@
+
+	.--foo.svelte-xyz {
+		color: red;
+	}
diff --git a/packages/svelte/tests/css/samples/double-hyphen/input.svelte b/packages/svelte/tests/css/samples/double-hyphen/input.svelte
new file mode 100644
index 000000000000..e2907f9344a4
--- /dev/null
+++ b/packages/svelte/tests/css/samples/double-hyphen/input.svelte
@@ -0,0 +1,7 @@
+<div class="--foo"></div>
+
+<style>
+	.--foo {
+		color: red;
+	}
+</style>
\ No newline at end of file