From 41d8d1fa2677b13ad5ca77d117c11584f03235c2 Mon Sep 17 00:00:00 2001
From: Cameron McHenry <camchenry@users.noreply.github.com>
Date: Tue, 1 Oct 2024 18:46:16 -0400
Subject: [PATCH] feat(minifier): fold object constructor

---
 .../peephole_substitute_alternate_syntax.rs   | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs b/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
index e925b0b85b4e72..e3e2dadc067bc8 100644
--- a/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
+++ b/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
@@ -1,4 +1,6 @@
+use oxc_allocator::Vec;
 use oxc_ast::ast::*;
+use oxc_semantic::IsGlobalReference;
 use oxc_span::{GetSpan, SPAN};
 use oxc_syntax::{
     number::NumberBase,
@@ -80,6 +82,9 @@ impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
         if !self.compress_undefined(expr, ctx) {
             self.compress_boolean(expr, ctx);
         }
+
+        self.compress_new_expression(expr, ctx);
+        self.compress_call_expression(expr, ctx);
     }
 
     fn exit_binary_expression(
@@ -260,6 +265,32 @@ impl<'a> PeepholeSubstituteAlternateSyntax {
             self.changed = true;
         }
     }
+
+    fn compress_new_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
+        if let Expression::NewExpression(new_expr) = expr {
+            // `new Object` -> `{}`
+            if new_expr.callee.is_global_reference_name("Object", ctx.symbols())
+                && new_expr.arguments.is_empty()
+            {
+                *expr =
+                    ctx.ast.expression_object(expr.span(), Vec::new_in(ctx.ast.allocator), None);
+                self.changed = true;
+            }
+        }
+    }
+
+    fn compress_call_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
+        if let Expression::CallExpression(call_expr) = expr {
+            // `Object()` -> `{}`
+            if call_expr.callee.is_global_reference_name("Object", ctx.symbols())
+                && call_expr.arguments.is_empty()
+            {
+                *expr =
+                    ctx.ast.expression_object(expr.span(), Vec::new_in(ctx.ast.allocator), None);
+                self.changed = true;
+            }
+        }
+    }
 }
 
 /// <https://github.com/google/closure-compiler/blob/master/test/com/google/javascript/jscomp/PeepholeSubstituteAlternateSyntax.java>
@@ -302,4 +333,13 @@ mod test {
         // shadowd
         test_same("(function(undefined) { let x = typeof undefined; })()");
     }
+
+    #[test]
+    fn fold_literal_object_constructors() {
+        test("x = new Object", "x = ({})");
+        test("x = new Object()", "x = ({})");
+        test("x = Object()", "x = ({})");
+
+        test_same("x = (function f(){function Object(){this.x=4}return new Object();})();");
+    }
 }