feat(css/minifier): Compress @import at-rule (#3850)

crates/swc_css_minifier/src/compress/at_rule.rs

@@ -0,0 +1,39 @@
+use swc_css_ast::*;
+use swc_css_visit::{VisitMut, VisitMutWith};
+
+pub fn compress_at_rule() -> impl VisitMut {
+    CompressAtRule {}
+}
+
+struct CompressAtRule {}
+
+impl VisitMut for CompressAtRule {
+    fn visit_mut_import_href(&mut self, import_href: &mut ImportHref) {
+        import_href.visit_mut_children_with(self);
+
+        if let ImportHref::Url(Url {
+            value: Some(value),
+            modifiers,
+            span,
+            ..
+        }) = import_href
+        {
+            if let Some(modifiers) = modifiers {
+                if !modifiers.is_empty() {
+                    return;
+                }
+            }
+
+            let new_value = match value {
+                UrlValue::Str(Str { value, .. }) => value,
+                UrlValue::Raw(UrlValueRaw { value, .. }) => value,
+            };
+
+            *import_href = ImportHref::Str(Str {
+                span: *span,
+                value: (&*new_value).into(),
+                raw: (&*new_value).into(),
+            });
+        }
+    }
+}

crates/swc_css_minifier/src/compress/mod.rs

@@ -1,5 +1,6 @@
 pub mod alpha_value;
 pub mod angle;
+pub mod at_rule;
 pub mod declaration;
 pub mod easing_function;
 pub mod empty;

crates/swc_css_minifier/src/lib.rs

@@ -4,10 +4,10 @@ use swc_css_ast::*;
 use swc_css_visit::VisitMutWith;
 
 use self::compress::{
-    alpha_value::compress_alpha_value, angle::compress_angle, declaration::compress_declaration,
-    easing_function::compress_easing_function, empty::compress_empty,
-    frequency::compress_frequency, keyframes::compress_keyframes, length::compress_length,
-    selector::compress_selector, time::compress_time,
+    alpha_value::compress_alpha_value, angle::compress_angle, at_rule::compress_at_rule,
+    declaration::compress_declaration, easing_function::compress_easing_function,
+    empty::compress_empty, frequency::compress_frequency, keyframes::compress_keyframes,
+    length::compress_length, selector::compress_selector, time::compress_time,
     transform_function::compress_transform_function, unicore_range::compress_unicode_range,
     url::compress_url,
 };
@@ -28,5 +28,5 @@ pub fn minify(stylesheet: &mut Stylesheet) {
     stylesheet.visit_mut_with(&mut compress_declaration());
     stylesheet.visit_mut_with(&mut compress_selector());
     stylesheet.visit_mut_with(&mut compress_keyframes());
-    stylesheet.visit_mut_with(&mut compress_selector());
+    stylesheet.visit_mut_with(&mut compress_at_rule());
 }

crates/swc_css_minifier/tests/fixture/compress-at-rule/input.css

@@ -0,0 +1,10 @@
+@import 'custom.css';
+@import url(custom.css);
+@import url(   custom.css   );
+@import url('custom.css');
+@import url("custom.css");
+@import url('custo(m.css');
+@import url('custom.css') screen and (orientation:landscape);
+@import url("fallback-layout.css") supports(not (display: flex));
+@import "mystyle.css" supports(display: flex);
+@import "mystyle.css" supports((display: flex));

crates/swc_css_minifier/tests/fixture/compress-at-rule/output.min.css

@@ -0,0 +1 @@
+@import"custom.css";@import"custom.css";@import"custom.css";@import"custom.css";@import"custom.css";@import"custo\\(m.css";@import"custom.css"screen and (orientation:landscape);@import"fallback-layout.css"supports(not (display:flex));@import"mystyle.css"supports(display:flex);@import"mystyle.css"supports((display:flex));