fix(minifier): drop debugger statements in unbraced bodies (#27867)

Replace debugger statements with empty statements during normalization so `dropDebugger` also removes them from unbraced `if`/`else`, loop, and labeled bodies. Add regressions covering these positions, preserved side effects, and `dropDebugger: false`.

Fixes #27866

crates/oxc_minifier/src/peephole/normalize.rs

@@ -101,15 +101,11 @@ impl<'a> Traverse<'a> for Normalize {
     fn exit_statements(
         &mut self,
         stmts: &mut ArenaVec<'a, Statement<'a>>,
-        ctx: &mut TraverseCtx<'a>,
+        _ctx: &mut TraverseCtx<'a>,
     ) {
         // No console handling here: `exit_expression` has already rewritten
         // every console call (statement position included) to `void 0`.
-        stmts.retain(|stmt| match stmt {
-            Statement::EmptyStatement(_) => false,
-            Statement::DebuggerStatement(_) if ctx.options().drop_debugger => false,
-            _ => true,
-        });
+        stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
     }
 
     fn exit_variable_declaration(
@@ -124,6 +120,10 @@ impl<'a> Traverse<'a> for Normalize {
 
     fn exit_statement(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
         match stmt {
+            Statement::DebuggerStatement(debugger) if ctx.options().drop_debugger => {
+                let new_stmt = Statement::new_empty_statement(debugger.span, ctx);
+                ctx.replace_statement(stmt, new_stmt);
+            }
             Statement::WhileStatement(_) if self.options.convert_while_to_fors => {
                 Self::convert_while_to_for(stmt, ctx);
             }

crates/oxc_minifier/tests/peephole/normalize.rs

@@ -78,7 +78,34 @@ fn drop_console_does_not_leak_references() {
 #[test]
 fn drop_debugger() {
     let options = CompressOptions { drop_debugger: true, ..default_options() };
+
     test_options("debugger", "", &options);
+    test_options(
+        "export function f(x) { debugger; if (x) debugger; return x }",
+        "export function f(x) { return x }",
+        &options,
+    );
+    test_options(
+        "export function f(x) { debugger; if (x) { debugger; } return x }",
+        "export function f(x) { return x }",
+        &options,
+    );
+    test_options("if (foo()) debugger", "foo()", &options);
+    test_options("if (x) debugger; else foo()", "x || foo()", &options);
+    test_options("if (x) foo(); else debugger", "x && foo()", &options);
+    test_options("while (foo()) debugger", "for (; foo(););", &options);
+    test_options("do debugger; while (foo())", "do; while (foo());", &options);
+    test_options("for (foo(); bar(); baz()) debugger", "for (foo(); bar(); baz());", &options);
+    test_options("for (var x in foo()) debugger", "for (var x in foo());", &options);
+    test_options("for (var x of foo()) debugger", "for (var x of foo());", &options);
+    test_options("label: debugger", "", &options);
+}
+
+#[test]
+fn keep_debugger() {
+    test_same("export function f(x) { debugger; if (x) debugger; return x }");
+    test_same("if (x) debugger; else debugger;");
+    test_same("for (; foo();) debugger;");
 }
 
 #[test]

tasks/track_memory_allocations/allocs_minifier.yaml

@@ -71,6 +71,6 @@ kitchen-sink.tsx:
   sys deallocs: 1854
   sys alloc bytes: 5304252 # 5.30 MB
   sys peak growth: 3707425 # 3.71 MB
-  arena allocs: 31111
+  arena allocs: 31112
   arena reallocs: 3012
   arena size: 8461040 # 8.46 MB