feat(minifier): remove empty class static block class Foo { static {} } (#8525)

crates/oxc_minifier/src/ast_passes/mod.rs

@@ -60,7 +60,7 @@ impl PeepholeOptimizations {
             x3_collapse_variable_declarations: CollapseVariableDeclarations::new(),
             x4_peephole_fold_constants: PeepholeFoldConstants::new(),
             x5_peephole_minimize_conditions: PeepholeMinimizeConditions::new(target),
-            x6_peephole_remove_dead_code: PeepholeRemoveDeadCode::new(),
+            x6_peephole_remove_dead_code: PeepholeRemoveDeadCode::new(in_fixed_loop),
             x7_convert_to_dotted_properties: ConvertToDottedProperties::new(in_fixed_loop),
             x8_peephole_replace_known_methods: PeepholeReplaceKnownMethods::new(),
             x9_peephole_substitute_alternate_syntax: PeepholeSubstituteAlternateSyntax::new(
@@ -149,6 +149,10 @@ impl<'a> Traverse<'a> for PeepholeOptimizations {
         self.x1_minimize_exit_points.exit_function_body(body, ctx);
     }
 
+    fn exit_class_body(&mut self, body: &mut ClassBody<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.x6_peephole_remove_dead_code.exit_class_body(body, ctx);
+    }
+
     fn exit_variable_declaration(
         &mut self,
         decl: &mut VariableDeclaration<'a>,
@@ -236,7 +240,7 @@ impl DeadCodeElimination {
     pub fn new() -> Self {
         Self {
             x1_peephole_fold_constants: PeepholeFoldConstants::new(),
-            x2_peephole_remove_dead_code: PeepholeRemoveDeadCode::new(),
+            x2_peephole_remove_dead_code: PeepholeRemoveDeadCode::new(false),
         }
     }
 }

crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs

@@ -17,6 +17,8 @@ use crate::{ctx::Ctx, keep_var::KeepVar, CompressorPass};
 /// <https://github.com/google/closure-compiler/blob/v20240609/src/com/google/javascript/jscomp/PeepholeRemoveDeadCode.java>
 pub struct PeepholeRemoveDeadCode {
     pub(crate) changed: bool,
+
+    in_fixed_loop: bool,
 }
 
 impl<'a> CompressorPass<'a> for PeepholeRemoveDeadCode {
@@ -70,11 +72,17 @@ impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
             self.changed = true;
         }
     }
+
+    fn exit_class_body(&mut self, body: &mut ClassBody<'a>, _ctx: &mut TraverseCtx<'a>) {
+        if !self.in_fixed_loop {
+            Self::remove_empty_class_static_block(body);
+        }
+    }
 }
 
 impl<'a, 'b> PeepholeRemoveDeadCode {
-    pub fn new() -> Self {
-        Self { changed: false }
+    pub fn new(in_fixed_loop: bool) -> Self {
+        Self { changed: false, in_fixed_loop }
     }
 
     /// Removes dead code thats comes after `return` statements after inlining `if` statements
@@ -562,6 +570,10 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
         };
         (params_empty && body_empty).then(|| ctx.ast.statement_empty(e.span))
     }
+
+    fn remove_empty_class_static_block(body: &mut ClassBody<'a>) {
+        body.body.retain(|e| !matches!(e, ClassElement::StaticBlock(s) if s.body.is_empty()));
+    }
 }
 
 /// <https://github.com/google/closure-compiler/blob/v20240609/test/com/google/javascript/jscomp/PeepholeRemoveDeadCodeTest.java>
@@ -573,7 +585,7 @@ mod test {
 
     fn test(source_text: &str, positive: &str) {
         let allocator = Allocator::default();
-        let mut pass = super::PeepholeRemoveDeadCode::new();
+        let mut pass = super::PeepholeRemoveDeadCode::new(false);
         tester::test(&allocator, source_text, positive, &mut pass);
     }
 
@@ -791,4 +803,10 @@ mod test {
         // test("/* @__PURE__ */ (() => x)()", "");
         // test("/* @__PURE__ */ (() => x)(y, z)", "y, z;");
     }
+
+    #[test]
+    fn test_remove_empty_static_block() {
+        test("class Foo { static {}; foo }", "class Foo { foo }");
+        test_same("class Foo { static { foo() }");
+    }
 }