commit d245f0769039e204442e07023797278350929255
parent 809803e19927059f7f167093c5b33977b36337fb
Author: sickl8 <sickl8@protonmail.com>
Date: Wed, 7 Jan 2026 13:47:43 +0000
Bug 1995187 - Add support for `#[css(keyword = "...")]` overrides in ToTyped derive. r=emilio,firefox-style-system-reviewers
Differential Revision: https://phabricator.services.mozilla.com/D275023
Diffstat:
1 file changed, 15 insertions(+), 16 deletions(-)
diff --git a/servo/components/style_derive/to_typed.rs b/servo/components/style_derive/to_typed.rs
@@ -33,8 +33,8 @@ use synstructure::{BindingInfo, Structure};
/// otherwise, they return `None`.
///
/// Unit variants are mapped to keywords using their Rust identifier converted
-/// via `to_css_identifier`. Attributes like `#[css(keyword = "...")]` are not
-/// yet supported in this path (see bug 1995187).
+/// via `to_css_identifier`. Attributes like `#[css(keyword = "...")]` will
+/// override the behavior and use the provided keyword instead.
///
/// For other kinds of types (e.g. unions), no `to_typed` method is generated;
/// the default implementation applies, which always returns `None`.
@@ -137,18 +137,19 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
/// `ToTyped` implementation.
///
/// * Unit variants are reified into `TypedValue::Keyword`, using the variant’s
-/// identifier converted with `cg::to_css_identifier`.
+/// identifier converted with `cg::to_css_identifier` or a custom keyword if
+/// provided through `#[css(keyword = "...")]`.
/// * Variants marked with `#[css(skip)]` or `#[typed_value(skip)]` or
/// `#[typed(todo)]` return `None`.
/// * Variants with fields delegate to `derive_variant_fields_expr()` when
/// `derive_fields` is enabled; otherwise they return `None`.
///
-/// Note: `#[css(keyword = "...")]` overrides are not handled in this
-/// `derive_variant_arm` path. This is fine for now because all existing cases
-/// that use such overrides (e.g. `#[css(keyword = "preserve-3d")]`) occur in
-/// pure keyword enums, which are covered by the all-unit `ToCss` path. Support
-/// will need to be added here once mixed enums with keyword overrides start
-/// implementing `ToTyped`.
+/// Note: `#[css(keyword = "...")]` overrides are now recognized in this
+/// `derive_variant_arm` path, but the support is not yet exercised because we
+/// currently have no mixed enums that use keyword overrides together with
+/// `ToTyped`. This keeps the behavior the same as before, all existing enums
+/// with keyword overrides (e.g. `#[css(keyword = "preserve-3d")]`) are still
+/// pure keyword enums and are handled through the all-unit `ToCss` path.
fn derive_variant_arm(
variant: &synstructure::VariantInfo,
derive_fields: bool,
@@ -171,11 +172,6 @@ fn derive_variant_arm(
return quote!(None);
}
- assert!(
- css_variant_attrs.keyword.is_none(),
- "Unhandled keyword attribute"
- );
-
// If the variant is explicitly marked #[typed_value(skip)] or
// #[typed_value(todo)], don’t generate anything for it, always return
// None.
@@ -186,9 +182,12 @@ fn derive_variant_arm(
// If the variant has no bindings (i.e. no data fields), treat it as a unit
// variant and reify it as a keyword.
if bindings.is_empty() {
- // Convert the Rust variant name into its CSS identifier form
+ // If #[css(keyword = "...")] is present, use it.
+ // Else convert the Rust variant name into its CSS identifier form
// (e.g. AvoidColumn -> "avoid-column").
- let keyword = cg::to_css_identifier(&identifier.to_string());
+ let keyword = css_variant_attrs
+ .keyword
+ .unwrap_or_else(|| cg::to_css_identifier(&identifier.to_string()));
// Emit code to wrap this keyword into a TypedValue.
quote! {
