From 96ea9960f742607da53a21cfa029bc0dc3dbf1ae Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Wed, 14 Feb 2024 22:34:49 -0500
Subject: [PATCH] Merge @keyframes with same name and prefixes

---
 src/lib.rs       | 33 +++++++++++++++++++++++++++++++++
 src/rules/mod.rs |  9 +++++++--
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 7e034ac6..d22bbf33 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7257,6 +7257,39 @@ mod tests {
         ..Browsers::default()
       },
     );
+
+    minify_test(
+      r#"
+      @keyframes test {
+        100% {
+          background: blue
+        }
+      }
+
+      @keyframes test {
+        100% {
+          background: red
+        }
+      }
+    "#,
+      "@keyframes test{to{background:red}}",
+    );
+    minify_test(
+      r#"
+      @keyframes test {
+        100% {
+          background: blue
+        }
+      }
+
+      @-webkit-keyframes test {
+        100% {
+          background: red
+        }
+      }
+    "#,
+      "@keyframes test{to{background:#00f}}@-webkit-keyframes test{to{background:red}}",
+    );
   }
 
   #[test]
diff --git a/src/rules/mod.rs b/src/rules/mod.rs
index 067848e4..89ac3087 100644
--- a/src/rules/mod.rs
+++ b/src/rules/mod.rs
@@ -519,10 +519,15 @@ impl<'i, T: Clone> CssRuleList<'i, T> {
             };
           }
 
-          // If there is an existing rule with the same name and identical keyframes,
-          // merge the vendor prefixes from this rule into it.
+          // Merge @keyframes rules with the same name.
           if let Some(existing_idx) = keyframe_rules.get(&keyframes.name) {
             if let Some(CssRule::Keyframes(existing)) = &mut rules.get_mut(*existing_idx) {
+              // If the existing rule has the same vendor prefixes, replace it with this rule.
+              if existing.vendor_prefix == keyframes.vendor_prefix {
+                *existing = keyframes.clone();
+                continue;
+              }
+              // Otherwise, if the keyframes are identical, merge the prefixes.
               if existing.keyframes == keyframes.keyframes {
                 existing.vendor_prefix |= keyframes.vendor_prefix;
                 set_prefix!(existing);