From 8f683e3f77fe9f4fd84a5bf64c067ae9526fb330 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Donny/=EA=B0=95=EB=8F=99=EC=9C=A4?= <kdy1997.dev@gmail.com>
Date: Fri, 13 Jan 2023 15:55:04 +0900
Subject: [PATCH] feat(es/minifier): Remove noop spreads (#6803)

**Related issue:**

 - Closes https://github.com/swc-project/swc/issues/6788.
---
 crates/swc_ecma_minifier/src/compress/pure/mod.rs     | 11 +++++++++++
 .../tests/pass-1/issue-6788/1/input.js                |  4 ++++
 .../tests/pass-1/issue-6788/1/output.js               |  1 +
 3 files changed, 16 insertions(+)
 create mode 100644 crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/input.js
 create mode 100644 crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/output.js

diff --git a/crates/swc_ecma_minifier/src/compress/pure/mod.rs b/crates/swc_ecma_minifier/src/compress/pure/mod.rs
index bba00a7f202..88cc235051f 100644
--- a/crates/swc_ecma_minifier/src/compress/pure/mod.rs
+++ b/crates/swc_ecma_minifier/src/compress/pure/mod.rs
@@ -12,6 +12,7 @@ use swc_ecma_visit::{noop_visit_mut_type, VisitMut, VisitMutWith, VisitWith};
 use tracing::{debug, span, Level};
 
 use self::{ctx::Ctx, misc::DropOpts};
+use super::util::is_pure_undefined_or_null;
 #[cfg(feature = "debug")]
 use crate::debug::dump;
 use crate::{
@@ -760,6 +761,16 @@ impl VisitMut for Pure<'_> {
 
     fn visit_mut_prop_or_spreads(&mut self, exprs: &mut Vec<PropOrSpread>) {
         self.visit_par(exprs);
+
+        exprs.retain(|e| {
+            if let PropOrSpread::Spread(spread) = e {
+                if is_pure_undefined_or_null(&self.expr_ctx, &spread.expr) {
+                    return false;
+                }
+            }
+
+            true
+        })
     }
 
     fn visit_mut_return_stmt(&mut self, s: &mut ReturnStmt) {
diff --git a/crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/input.js b/crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/input.js
new file mode 100644
index 00000000000..46ea2c7eee4
--- /dev/null
+++ b/crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/input.js
@@ -0,0 +1,4 @@
+const foo = { ...(null && {}) };
+const bar = { ...null };
+
+console.log(foo, bar);
diff --git a/crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/output.js b/crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/output.js
new file mode 100644
index 00000000000..555a3c0eadb
--- /dev/null
+++ b/crates/swc_ecma_minifier/tests/pass-1/issue-6788/1/output.js
@@ -0,0 +1 @@
+console.log({}, {});