feat(minifier): remove last redundant return statement (#8523)

crates/oxc_minifier/src/ast_passes/minimize_exit_points.rs

@@ -1,5 +1,6 @@
+use oxc_allocator::Vec;
 use oxc_ast::ast::*;
-use oxc_traverse::{traverse_mut_with_ctx, ReusableTraverseCtx, Traverse};
+use oxc_traverse::{traverse_mut_with_ctx, ReusableTraverseCtx, Traverse, TraverseCtx};
 
 use crate::CompressorPass;
 
@@ -18,12 +19,26 @@ impl<'a> CompressorPass<'a> for MinimizeExitPoints {
     }
 }
 
-impl Traverse<'_> for MinimizeExitPoints {}
+impl Traverse<'_> for MinimizeExitPoints {
+    fn exit_function_body(&mut self, body: &mut FunctionBody<'_>, _ctx: &mut TraverseCtx<'_>) {
+        self.remove_last_return(&mut body.statements);
+    }
+}
 
-impl MinimizeExitPoints {
+impl<'a> MinimizeExitPoints {
     pub fn new() -> Self {
         Self { changed: false }
     }
+
+    // `function foo() { return }` -> `function foo() {}`
+    fn remove_last_return(&mut self, stmts: &mut Vec<'a, Statement<'a>>) {
+        if let Some(last) = stmts.last() {
+            if matches!(last, Statement::ReturnStatement(ret) if ret.argument.is_none()) {
+                stmts.pop();
+                self.changed = true;
+            }
+        }
+    }
 }
 
 #[cfg(test)]
@@ -71,7 +86,6 @@ mod test {
     }
 
     #[test]
-    #[ignore]
     fn test_function_return_optimization1() {
         fold("function f(){return}", "function f(){}");
     }
@@ -140,7 +154,6 @@ mod test {
     }
 
     #[test]
-    #[ignore]
     fn test_function_return_scoped() {
         fold_same(
             "function f(a) {
@@ -366,7 +379,6 @@ mod test {
     }
 
     #[test]
-    #[ignore]
     fn test_dont_remove_break_in_try_finally() {
         fold_same("function f() {b:try{throw 9} finally {break b} return 1;}");
     }
@@ -378,7 +390,6 @@ mod test {
      * @see https://github.com/google/closure-compiler/issues/554
      */
     #[test]
-    #[ignore]
     fn test_dont_fold_break_in_do_while_if_condition_has_side_effects() {
         fold_same("var b=true;do{break}while(b=false);");
     }

crates/oxc_minifier/src/ast_passes/mod.rs

@@ -130,7 +130,6 @@ impl<'a> Traverse<'a> for PeepholeOptimizations {
 
     fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
         self.x0_statement_fusion.exit_statements(stmts, ctx);
-        self.x1_minimize_exit_points.exit_statements(stmts, ctx);
         self.x2_exploit_assigns.exit_statements(stmts, ctx);
         self.x3_collapse_variable_declarations.exit_statements(stmts, ctx);
         self.x5_peephole_minimize_conditions.exit_statements(stmts, ctx);

crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs

@@ -27,6 +27,13 @@ impl<'a> CompressorPass<'a> for PeepholeRemoveDeadCode {
 }
 
 impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
+    fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
+        if stmts.iter().any(|stmt| matches!(stmt, Statement::EmptyStatement(_))) {
+            stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
+        }
+        self.dead_code_elimination(stmts, Ctx(ctx));
+    }
+
     fn exit_statement(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
         let ctx = Ctx(ctx);
         if let Some(new_stmt) = match stmt {
@@ -50,13 +57,6 @@ impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
         }
     }
 
-    fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
-        if stmts.iter().any(|stmt| matches!(stmt, Statement::EmptyStatement(_))) {
-            stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
-        }
-        self.dead_code_elimination(stmts, Ctx(ctx));
-    }
-
     fn exit_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
         let ctx = Ctx(ctx);
         if let Some(folded_expr) = match expr {

tasks/minsize/minsize.snap

@@ -15,13 +15,13 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 
 1.01 MB    | 460.17 kB  | 458.89 kB  | 126.76 kB  | 126.71 kB  | bundle.min.js
 
-1.25 MB    | 652.84 kB  | 646.76 kB  | 163.54 kB  | 163.73 kB  | three.js  
+1.25 MB    | 652.80 kB  | 646.76 kB  | 163.53 kB  | 163.73 kB  | three.js  
 
-2.14 MB    | 725.68 kB  | 724.14 kB  | 180.07 kB  | 181.07 kB  | victory.js
+2.14 MB    | 725.52 kB  | 724.14 kB  | 180.05 kB  | 181.07 kB  | victory.js
 
-3.20 MB    | 1.01 MB    | 1.01 MB    | 331.79 kB  | 331.56 kB  | echarts.js
+3.20 MB    | 1.01 MB    | 1.01 MB    | 331.77 kB  | 331.56 kB  | echarts.js
 
-6.69 MB    | 2.32 MB    | 2.31 MB    | 492.64 kB  | 488.28 kB  | antd.js   
+6.69 MB    | 2.32 MB    | 2.31 MB    | 492.62 kB  | 488.28 kB  | antd.js   
 
-10.95 MB   | 3.49 MB    | 3.49 MB    | 907.42 kB  | 915.50 kB  | typescript.js
+10.95 MB   | 3.49 MB    | 3.49 MB    | 907.11 kB  | 915.50 kB  | typescript.js