Skip to content

fix(emotion): Handle React Compiler output without panicking #636

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Donny/강동윤 (kdy1) merged 3 commits into from
Jun 30, 2026
Merged

fix(emotion): Handle React Compiler output without panicking #636

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
e7fb667
fix(emotion): Handle synthetic React Compiler spans
scttcper Jun 29, 2026
69eede5
test(emotion): Trim React Compiler regression
scttcper Jun 29, 2026
f83c16d
fix(emotion): Keep source hash behavior
scttcper Jun 30, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions .changeset/quiet-emotion-spans.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@swc/plugin-emotion": patch
---

Handle React Compiler output with synthetic spans.
2 changes: 1 addition & 1 deletion package.json
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@
},
"devDependencies": {
"@changesets/cli": "^2.27.1",
"@swc/core": "^1.15.40",
"@swc/core": "^1.15.43",

@scttcper Scott Cooper (scttcper) Jun 29, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

needed so the wasm test actually exercises reactCompiler; 1.15.40 rejects the option before it reaches the plugin.

"@taplo/cli": "^0.7.0",
"@types/node": "^22.13.9",
"husky": "^9.0.11",
Expand Down
33 changes: 33 additions & 0 deletions packages/emotion/__tests__/wasm.test.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -123,3 +123,36 @@ test("Should keep plain keyframes label for namespace imports", async () => {
);
expect(output.code).not.toContain("label:pulse");
});

test("Should transform css prop output from React Compiler", async () => {
const output = await transform(
`
import { css } from "@emotion/react";

export function App() {
return <div css={css\`width:120px;\`} />;
}
`,
{
envName: "development",
jsc: {
parser: {
syntax: "ecmascript",
jsx: true,
},
transform: {
react: {
runtime: "automatic",
importSource: "@emotion/react",
},
reactCompiler: true,
},
experimental: {
plugins: [[pluginPath, {}]],
},
},
} satisfies Options,
);

expect(output.code).toContain('css("width:120px;", "")');
});
30 changes: 21 additions & 9 deletions packages/emotion/transform/src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -258,6 +258,14 @@ impl<'a, C: Comments> EmotionTransformer<'a, C> {
label
}

fn add_pure_comment(&self, pos: BytePos) {
// React Compiler can synthesize Emotion calls with dummy spans.
// SWC cannot attach comments at BytePos(0), so skip the hint there.
if pos != BytePos(0) {
self.comments.add_pure_comment(pos);
}
}

fn create_call_label_arg(&self, kind: ExprKind) -> ExprOrSpread {
self.create_runtime_label(kind, false).as_arg()
}
Expand All @@ -267,6 +275,10 @@ impl<'a, C: Comments> EmotionTransformer<'a, C> {
}

fn create_sourcemap(&mut self, pos: BytePos) -> Option<String> {
if pos == BytePos(0) {
return None;
}

if self.options.sourcemap.unwrap_or(false) {
let loc = self.cm.get_code_map().lookup_char_pos(pos);
let filename = self.filepath.to_str().map(BytesStr::from_str_slice);
Expand Down Expand Up @@ -527,7 +539,7 @@ impl<'a, C: Comments> EmotionTransformer<'a, C> {
args.push(cm.as_arg());
}

self.comments.add_pure_comment(expr_pos);
self.add_pure_comment(expr_pos);
let call_span = Span::new(expr_pos, expr_pos);

let callee = match &css_callee {
Expand Down Expand Up @@ -582,7 +594,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
if matches!(*kind, ExprKind::Css | ExprKind::Keyframes)
&& !self.in_jsx_element
{
self.comments.add_pure_comment(expr.span.lo());
self.add_pure_comment(expr.span.lo());
if self.options.auto_label.unwrap_or(false) {
expr.args.push(self.create_call_label_arg(*kind));
}
Expand All @@ -608,7 +620,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
if !c.args.is_empty() {
let mut args_props = Vec::with_capacity(2);
args_props.push(self.create_label_prop_node("target"));
self.comments.add_pure_comment(expr.span.lo());
self.add_pure_comment(expr.span.lo());
if self.options.auto_label.unwrap_or(false) {
args_props.push(PropOrSpread::Prop(Box::new(
Prop::KeyValue(KeyValueProp {
Expand Down Expand Up @@ -678,7 +690,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
args_props.push(self.create_label_prop_node("target"));
let mut args = vec![prop.sym.as_ref().as_arg()];
if !self.in_jsx_element {
self.comments.add_pure_comment(expr.span.lo());
self.add_pure_comment(expr.span.lo());
if self.options.auto_label.unwrap_or(false) {
args_props.push(PropOrSpread::Prop(Box::new(
Prop::KeyValue(KeyValueProp {
Expand Down Expand Up @@ -724,7 +736,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
.iter()
.find_map(|item| match_runtime_export(item, &m.prop))
{
self.comments.add_pure_comment(expr.span.lo());
self.add_pure_comment(expr.span.lo());
if self.options.auto_label.unwrap_or(false) {
expr.args.push(self.create_call_label_arg(kind));
}
Expand Down Expand Up @@ -787,7 +799,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
let mut callee = call.take();
let mut object_props = Vec::with_capacity(2);
object_props.push(self.create_label_prop_node("target"));
self.comments.add_pure_comment(callee.span.lo());
self.add_pure_comment(callee.span.lo());
if self.options.auto_label.unwrap_or(false) {
object_props.push(PropOrSpread::Prop(Box::new(
Prop::KeyValue(KeyValueProp {
Expand Down Expand Up @@ -864,7 +876,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
if matches!(*kind, ExprKind::Css | ExprKind::Keyframes) {
let mut args = self.create_args_from_tagged_tpl(&mut tagged_tpl.tpl);
if !self.in_jsx_element {
self.comments.add_pure_comment(i.span.lo());
self.add_pure_comment(i.span.lo());
if self.options.auto_label.unwrap_or(false) {
args.push(self.create_tagged_tpl_label_arg(*kind));
}
Expand Down Expand Up @@ -911,7 +923,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
args.push(cm.as_arg());
}

self.comments.add_pure_comment(member_expr.span.lo());
self.add_pure_comment(member_expr.span.lo());
return Expr::Call(CallExpr {
callee: CallExpr {
callee: i.take().as_callee(),
Expand All @@ -935,7 +947,7 @@ impl<C: Comments> Fold for EmotionTransformer<'_, C> {
if let Some(kind) = c.exported_names.iter().find_map(|item| {
match_runtime_export(item, &member_expr.prop)
}) {
self.comments.add_pure_comment(member_expr.span.lo());
self.add_pure_comment(member_expr.span.lo());
return Expr::Call(CallExpr {
callee: member_expr.take().as_callee(),
args: {
Expand Down
Loading
Loading