fix(ecma/codegen): don't print trailing coma for rest argument

crates/swc_ecma_codegen/src/ctx.rs

@@ -0,0 +1,55 @@
+use std::ops::{Deref, DerefMut};
+
+use swc_common::SourceMapper;
+use swc_ecma_ast::SourceMapperExt;
+
+use crate::{text_writer::WriteJs, Emitter};
+
+impl<'a, 'b, W, S: SourceMapper> Emitter<'a, W, S>
+where
+    W: WriteJs,
+    S: SourceMapperExt,
+{
+    /// Original context is restored when returned guard is dropped.
+    #[inline]
+    pub(super) fn with_ctx(&mut self, ctx: Ctx) -> WithCtx<'b, W, S> {
+        let orig_ctx = self.ctx;
+
+        self.ctx = ctx;
+
+        WithCtx {
+            orig_ctx,
+            inner: self,
+        }
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy)]
+pub(crate) struct Ctx {
+    pub in_function_params: bool,
+}
+
+pub(super) struct WithCtx<'w, I: 'w + WriteJs, S: 'w + SourceMapper + SourceMapperExt> {
+    inner: &'w mut Emitter<'w, I, S>,
+    orig_ctx: Ctx,
+}
+
+impl<'w, I: 'w + WriteJs, S: 'w + SourceMapper + SourceMapperExt> Deref for WithCtx<'w, I, S> {
+    type Target = Emitter<'w, I, S>;
+
+    fn deref(&self) -> &Emitter<'w, I, S> {
+        self.inner
+    }
+}
+
+impl<'w, I: 'w + WriteJs, S: 'w + SourceMapper + SourceMapperExt> DerefMut for WithCtx<'w, I, S> {
+    fn deref_mut(&mut self) -> &mut Emitter<'w, I, S> {
+        self.inner
+    }
+}
+
+impl<'w, I: 'w + WriteJs, S: 'w + SourceMapper + SourceMapperExt> Drop for WithCtx<'w, I, S> {
+    fn drop(&mut self) {
+        self.inner.ctx = self.orig_ctx;
+    }
+}

crates/swc_ecma_codegen/src/lib.rs

@@ -2481,23 +2481,12 @@ where
         self.emit_leading_comments_of_span(node.span(), false)?;
 
         srcmap!(node, true);
-
-        let is_last_rest = match node.props.last() {
-            Some(ObjectPatProp::Rest(..)) => true,
-            _ => false,
-        };
-        let format = if is_last_rest {
-            ListFormat::ObjectBindingPatternElements ^ ListFormat::AllowTrailingComma
-        } else {
-            ListFormat::ObjectBindingPatternElements
-        };
-
         punct!("{");
 
         self.emit_list(
             node.span(),
             Some(&node.props),
-            format | ListFormat::CanSkipTrailingComma,
+            ListFormat::ObjectBindingPatternElements | ListFormat::CanSkipTrailingComma,
         )?;
 
         punct!("}");

crates/swc_ecma_codegen/tests/fixture/issue-6589/js/input.js

@@ -0,0 +1,14 @@
+export function func({a, b, ...rest}) {
+    console.log(a,b, rest)
+}
+
+const other = { unknow: "foo" }
+
+let foo = {
+    ...other,
+    bar: "baz"
+};
+let bar = {
+    bar: "baz",
+    ...other
+};

crates/swc_ecma_codegen/tests/fixture/issue-6589/js/output.js

@@ -0,0 +1,14 @@
+export function func({ a , b , ...rest }) {
+    console.log(a, b, rest);
+}
+const other = {
+    unknow: "foo"
+};
+let foo = {
+    ...other,
+    bar: "baz"
+};
+let bar = {
+    bar: "baz",
+    ...other
+};

crates/swc_ecma_codegen/tests/fixture/issue-6589/js/output.min.js

@@ -0,0 +1 @@
+export function func({a,b,...rest}){console.log(a,b,rest)}const other={unknow:"foo"};let foo={...other,bar:"baz"};let bar={bar:"baz",...other};

crates/swc_ecma_codegen/tests/fixture/issue-6589/ts/input.ts

@@ -0,0 +1,21 @@
+export function func({
+ a,
+ b,
+ ...rest
+}: {
+    a: string,
+    b: string,
+}) {
+    console.log(a,b, rest)
+}
+
+const other = { unknow: "foo" }
+
+let foo = {
+    ...other,
+    bar: "baz"
+};
+let bar = {
+    bar: "baz",
+    ...other
+};

crates/swc_ecma_codegen/tests/fixture/issue-6589/ts/output.ts

@@ -0,0 +1,17 @@
+export function func({ a , b , ...rest }: {
+    a: string;
+    b: string;
+}) {
+    console.log(a, b, rest);
+}
+const other = {
+    unknow: "foo"
+};
+let foo = {
+    ...other,
+    bar: "baz"
+};
+let bar = {
+    bar: "baz",
+    ...other
+};