From 00ccbdc93792db77e5eefe508f4e502b8b80f686 Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Fri, 20 Dec 2024 09:22:49 -0500
Subject: [PATCH] =?UTF-8?q?Don=E2=80=99t=20detect=20arbitrary=20properties?=
 =?UTF-8?q?=20when=20preceded=20by=20an=20escape=20(#15456)?=
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This is a targeted bug fix uncovered by the v4 docs.

Given this code:
```html
<!-- [!code word:group-has-\\[a\\]\\:block] -->
```

We'd pick up `[a\\]\\:block]` as a candidate which would then make it
far enough to get output to CSS and throw an error. This makes sure we
don't try to start an arbitrary property if the preceding character is a
`\`

cc @RobinMalfait this look okay?

---------

Co-authored-by: Robin Malfait <malfait.robin@gmail.com>
---
 CHANGELOG.md               |  1 +
 crates/oxide/src/parser.rs | 16 +++++++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2ecc63017..0435312a3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Use the correct property value for `place-content-between`, `place-content-around`, and `place-content-evenly` utilities ([#15440](https://github.com/tailwindlabs/tailwindcss/pull/15440))
+- Don’t detect arbitrary properties when preceded by an escape ([#15456](https://github.com/tailwindlabs/tailwindcss/pull/15456))
 
 ### Changed
 
diff --git a/crates/oxide/src/parser.rs b/crates/oxide/src/parser.rs
index 281774261..1c8fdf75c 100644
--- a/crates/oxide/src/parser.rs
+++ b/crates/oxide/src/parser.rs
@@ -595,7 +595,7 @@ impl<'a> Extractor<'a> {
     fn parse_start(&mut self) -> ParseAction<'a> {
         match self.cursor.curr {
             // Enter arbitrary property mode
-            b'[' => {
+            b'[' if self.cursor.prev != b'\\' => {
                 trace!("Arbitrary::Start\t");
                 self.arbitrary = Arbitrary::Brackets {
                     start_idx: self.cursor.pos,
@@ -1634,4 +1634,18 @@ mod test {
             ]
         );
     }
+
+    #[test]
+    fn arbitrary_properties_are_not_picked_up_after_an_escape() {
+        _please_trace();
+        let candidates = run(
+            r#"
+              <!-- [!code word:group-has-\\[a\\]\\:block] -->
+              \\[a\\]\\:block]
+            "#,
+            false,
+        );
+
+        assert_eq!(candidates, vec!["!code", "a"]);
+    }
 }