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feat(css-serializer): support custom properties in keyframes #2429

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Merged
luhc228 merged 1 commit into from
Apr 8, 2026
Merged

feat(css-serializer): support custom properties in keyframes #2429

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5 changes: 5 additions & 0 deletions .changeset/thin-shrimps-sip.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@lynx-js/css-serializer": patch
---

feat: support custom property declaration in keyframe rule
30 changes: 17 additions & 13 deletions packages/tools/css-serializer/src/parse.ts
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Expand Up @@ -117,6 +117,21 @@ function transformDeclaration(
}
}

function transformVariables(block: csstree.Block): Record<string, string> {
return Object.fromEntries(
block.children.toArray().filter((node) => {
return node.type === 'Declaration' && node.property.startsWith('--');
}).map((node) => {
const declaration = node as csstree.Declaration;
return [
declaration.property,
toString(declaration.value)
+ (declaration.important ? ' !important' : ''),
];
}),
);
}

function transformStyleRule(
node: csstree.Rule,
errors: ParserError[],
Expand All @@ -129,19 +144,7 @@ function transformStyleRule(
value: preludeText,
loc: toLoc(node.prelude.loc!.end),
},
variables: Object.fromEntries(
node.block.children.toArray().filter(node =>
node.type === 'Declaration' && node.property.startsWith('--')
).map((node) => {
return [
(node as csstree.Declaration).property,
toString((node as csstree.Declaration).value)
+ ((node as csstree.Declaration).important
? ' !important'
: ''),
];
}),
),
variables: transformVariables(node.block),
};
}

Expand Down Expand Up @@ -337,6 +340,7 @@ export function parse(content: string, options: {
value: preludeText,
loc: toLoc(rule.prelude.loc!.start, preludeText.length),
},
variables: transformVariables(rule.block),
style: transformBlock(rule.block, errors),
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};
}),
Expand Down
1 change: 1 addition & 0 deletions packages/tools/css-serializer/src/types/LynxStyleNode.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ export interface ImportRule {
}
export interface KeyframesStyle {
keyText: Value;
variables: Record<string, string>;
style: Declaration[];
}
export interface KeyframesRule {
Expand Down
17 changes: 17 additions & 0 deletions packages/tools/css-serializer/test/__preparation__/keyframes.css
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Expand Up @@ -33,3 +33,20 @@
c: none;
}
}

@keyframes test-keyframe-declaration {
0% {
--bg-color: red;
background-color: var(--bg-color);
}

50% {
--bg-color: green;
background-color: var(--bg-color);
}

100% {
--bg-color: blue;
background-color: var(--bg-color);
}
}
115 changes: 115 additions & 0 deletions packages/tools/css-serializer/test/__snapshots__/lynx.spec.ts.snap
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Expand Up @@ -2030,6 +2030,7 @@ exports[`keyframes 1`] = `
"value": "translateX(0%)",
},
],
"variables": {},
},
{
"keyText": {
Expand All @@ -2053,6 +2054,7 @@ exports[`keyframes 1`] = `
"value": "translateX(100%)",
},
],
"variables": {},
},
],
"type": "KeyframesRule",
Expand Down Expand Up @@ -2100,6 +2102,7 @@ exports[`keyframes 1`] = `
"value": "0",
},
],
"variables": {},
},
{
"keyText": {
Expand All @@ -2123,6 +2126,7 @@ exports[`keyframes 1`] = `
"value": "50px",
},
],
"variables": {},
},
{
"keyText": {
Expand All @@ -2146,6 +2150,7 @@ exports[`keyframes 1`] = `
"value": "50px",
},
],
"variables": {},
},
{
"keyText": {
Expand Down Expand Up @@ -2181,6 +2186,7 @@ exports[`keyframes 1`] = `
"value": "100%",
},
],
"variables": {},
},
],
"type": "KeyframesRule",
Expand Down Expand Up @@ -2216,6 +2222,7 @@ exports[`keyframes 1`] = `
"value": "1",
},
],
"variables": {},
},
{
"keyText": {
Expand Down Expand Up @@ -2251,6 +2258,7 @@ exports[`keyframes 1`] = `
"value": "3",
},
],
"variables": {},
},
{
"keyText": {
Expand All @@ -2274,6 +2282,7 @@ exports[`keyframes 1`] = `
"value": "5",
},
],
"variables": {},
},
{
"keyText": {
Expand All @@ -2297,6 +2306,112 @@ exports[`keyframes 1`] = `
"value": "none",
},
],
"variables": {},
},
],
"type": "KeyframesRule",
},
{
"name": {
"loc": {
"column": 37,
"line": 37,
},
"value": "test-keyframe-declaration",
},
"styles": [
{
"keyText": {
"loc": {
"column": 5,
"line": 38,
},
"value": "0%",
},
"style": [
{
"defaultValue": "",
"defaultValueMap": {
"--bg-color": "",
},
"keyLoc": {
"column": 21,
"line": 40,
},
"name": "background-color",
"type": "css_var",
"valLoc": {
"column": 39,
"line": 40,
},
"value": "{{--bg-color}}",
},
],
"variables": {
"--bg-color": "red",
},
},
{
"keyText": {
"loc": {
"column": 6,
"line": 43,
},
"value": "50%",
},
"style": [
{
"defaultValue": "",
"defaultValueMap": {
"--bg-color": "",
},
"keyLoc": {
"column": 21,
"line": 45,
},
"name": "background-color",
"type": "css_var",
"valLoc": {
"column": 39,
"line": 45,
},
"value": "{{--bg-color}}",
},
],
"variables": {
"--bg-color": "green",
},
},
{
"keyText": {
"loc": {
"column": 7,
"line": 48,
},
"value": "100%",
},
"style": [
{
"defaultValue": "",
"defaultValueMap": {
"--bg-color": "",
},
"keyLoc": {
"column": 21,
"line": 50,
},
"name": "background-color",
"type": "css_var",
"valLoc": {
"column": 39,
"line": 50,
},
"value": "{{--bg-color}}",
},
],
"variables": {
"--bg-color": "blue",
},
},
],
"type": "KeyframesRule",
Expand Down
2 changes: 2 additions & 0 deletions packages/web-platform/web-core/tests/__snapshots__/encode.spec.ts.snap
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Expand Up @@ -21,3 +21,5 @@ exports[`encodeCSS > scoped css 1`] = `".foo:where([l-css-id="1"]):not([l-e-name
exports[`encodeCSS > scoped css, 2 css id 1`] = `".foo:where([l-css-id="1"]):not([l-e-name]),.foo:where([l-css-id="2"]):not([l-e-name]){background:red;}"`;

exports[`encodeCSS > scoped css, import non existing 1`] = `".foo:where([l-css-id="1"]):not([l-e-name]),.foo:where([l-css-id="20"]):not([l-e-name]),.foo:where([l-css-id="2"]):not([l-e-name]){background:red;}"`;

exports[`encodeCSS > should encode KeyframesRule with CSS variables 1`] = `"@keyframes my-animation-with-vars{from{--my-var:0;opacity:{{--my-var}};}to{--my-var:1;opacity:{{--my-var}};}}"`;
25 changes: 25 additions & 0 deletions packages/web-platform/web-core/tests/encode.spec.ts
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Expand Up @@ -124,6 +124,31 @@ describe('encodeCSS', () => {
expect(buffer.length).toBeGreaterThan(0);
});

test('should encode KeyframesRule with CSS variables', () => {
const css = `
@keyframes my-animation-with-vars {
from {
--my-var: 0;
opacity: var(--my-var);
}
to {
--my-var: 1;
opacity: var(--my-var);
}
}
`;
const cssMap = {
'1': CSS.parse(css).root,
};
const buffer = encodeCSS(cssMap);
expect(buffer).toBeInstanceOf(Uint8Array);
expect(buffer.length).toBeGreaterThan(0);
const decodedString = get_style_content(
decode_style_info(buffer, undefined, true),
);
expect(decodedString.trim()).toMatchSnapshot();
});

test('should handle complex selectors', () => {
const css = `
div > .foo + #bar[attr="val"]::before:hover {
Expand Down
6 changes: 6 additions & 0 deletions packages/web-platform/web-core/ts/encode/encodeCSS.ts
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Expand Up @@ -59,6 +59,12 @@ export function encodeCSS(

keyFrameChildrenRule.set_prelude(prelude);

for (
const [key, value] of Object.entries(keyframesStyle.variables ?? {})
) {
keyFrameChildrenRule.push_declaration(key, value);
}

for (const decl of keyframesStyle.style) {
keyFrameChildrenRule.push_declaration(decl.name, decl.value);
}
Expand Down
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