From 19eb962a9a3f2d1bb928263e06b3fc107ab328d5 Mon Sep 17 00:00:00 2001
From: chenyang <chenyang@adastralab.ai>
Date: Sun, 5 Jul 2026 21:39:15 +0800
Subject: [PATCH 1/2] fix: reading an unset style property returns "" per
 CSSOM, not undefined
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Reading a property that is not set — via `el.style.someProp` or
`el.style.getPropertyValue("some-prop")` — returned undefined, but CSSOM
defines both as the empty string (the property getter is routed through the
same handler as getPropertyValue). Callers that assume the spec, e.g.
`el.style.color.replaceAll(...)`, crash on the undefined. Normalize an absent
property to "" in the style getter.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 cjs/interface/css-style-declaration.js  | 5 ++++-
 esm/interface/css-style-declaration.js  | 5 ++++-
 test/interface/css-style-declaration.js | 4 ++++
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/cjs/interface/css-style-declaration.js b/cjs/interface/css-style-declaration.js
index 726ab982..217f92ea 100644
--- a/cjs/interface/css-style-declaration.js
+++ b/cjs/interface/css-style-declaration.js
@@ -36,7 +36,10 @@ const handler = {
       return getKeys(style).length;
     if (/^\d+$/.test(name))
       return getKeys(style)[name];
-    return style.get(uhyphen(name));
+    // Per CSSOM, reading a property that is not set returns the empty string,
+    // not undefined (which also matches getPropertyValue, routed here).
+    const value = style.get(uhyphen(name));
+    return value === void 0 ? '' : value;
   },
 
   set(style, name, value) {
diff --git a/esm/interface/css-style-declaration.js b/esm/interface/css-style-declaration.js
index 7b8de0ac..89fc7801 100644
--- a/esm/interface/css-style-declaration.js
+++ b/esm/interface/css-style-declaration.js
@@ -35,7 +35,10 @@ const handler = {
       return getKeys(style).length;
     if (/^\d+$/.test(name))
       return getKeys(style)[name];
-    return style.get(uhyphen(name));
+    // Per CSSOM, reading a property that is not set returns the empty string,
+    // not undefined (which also matches getPropertyValue, routed here).
+    const value = style.get(uhyphen(name));
+    return value === void 0 ? '' : value;
   },
 
   set(style, name, value) {
diff --git a/test/interface/css-style-declaration.js b/test/interface/css-style-declaration.js
index 767863f9..baa5af2f 100644
--- a/test/interface/css-style-declaration.js
+++ b/test/interface/css-style-declaration.js
@@ -6,6 +6,10 @@ const {document} = parseHTML('');
 
 let node = document.createElement('div');
 assert(node.style.cssText, '', 'empty style');
+// Per CSSOM, an unset property reads as the empty string, not undefined —
+// matching getPropertyValue, which is routed through the same getter.
+assert(node.style.color, '', 'unset property getter returns ""');
+assert(node.style.getPropertyValue('color'), '', 'unset getPropertyValue returns ""');
 node.style.cssText = 'background-color: blue; background-image: url("https://t.co/i.png");';
 assert(node.style.backgroundColor, 'blue', 'style getter');
 assert(node.style.backgroundImage, 'url("https://t.co/i.png")', 'style value with colon');

From e1dd1da5d607ea2cf0ff7da746bd6314775386dc Mon Sep 17 00:00:00 2001
From: chenyang <chenyang@adastralab.ai>
Date: Wed, 8 Jul 2026 01:12:43 +0800
Subject: [PATCH 2/2] Apply CSSStyleDeclaration review suggestion

---
 cjs/interface/css-style-declaration.js | 5 +----
 esm/interface/css-style-declaration.js | 5 +----
 2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/cjs/interface/css-style-declaration.js b/cjs/interface/css-style-declaration.js
index 217f92ea..845be4d9 100644
--- a/cjs/interface/css-style-declaration.js
+++ b/cjs/interface/css-style-declaration.js
@@ -36,10 +36,7 @@ const handler = {
       return getKeys(style).length;
     if (/^\d+$/.test(name))
       return getKeys(style)[name];
-    // Per CSSOM, reading a property that is not set returns the empty string,
-    // not undefined (which also matches getPropertyValue, routed here).
-    const value = style.get(uhyphen(name));
-    return value === void 0 ? '' : value;
+    return style.get(uhyphen(name)) ?? '';
   },
 
   set(style, name, value) {
diff --git a/esm/interface/css-style-declaration.js b/esm/interface/css-style-declaration.js
index 89fc7801..deb8b59a 100644
--- a/esm/interface/css-style-declaration.js
+++ b/esm/interface/css-style-declaration.js
@@ -35,10 +35,7 @@ const handler = {
       return getKeys(style).length;
     if (/^\d+$/.test(name))
       return getKeys(style)[name];
-    // Per CSSOM, reading a property that is not set returns the empty string,
-    // not undefined (which also matches getPropertyValue, routed here).
-    const value = style.get(uhyphen(name));
-    return value === void 0 ? '' : value;
+    return style.get(uhyphen(name)) ?? '';
   },
 
   set(style, name, value) {