fix trailing comma (#1574)

Signed-off-by: Jess Frazelle <github@jessfraz.com>

src/wasm-lib/kcl/src/ast/types.rs

@@ -3511,6 +3511,33 @@ show(mySuperCoolPart)
         );
     }
 
+    #[test]
+    fn test_recast_trailing_comma() {
+        let some_program_string = r#"startSketchOn('XY')
+  |> startProfileAt([0, 0], %)
+  |> arc({
+    radius: 1,
+    angle_start: 0,
+    angle_end: 180,
+  }, %)"#;
+        let tokens = crate::token::lexer(some_program_string);
+        let parser = crate::parser::Parser::new(tokens);
+        let program = parser.ast().unwrap();
+
+        let recasted = program.recast(&Default::default(), 0);
+        assert_eq!(
+            recasted,
+            r#"startSketchOn('XY')
+  |> startProfileAt([0, 0], %)
+  |> arc({
+       radius: 1,
+       angle_start: 0,
+       angle_end: 180
+     }, %)
+"#
+        );
+    }
+
     #[test]
     fn test_recast_negative_var() {
         let some_program_string = r#"const w = 20

src/wasm-lib/kcl/src/parser/parser_impl.rs

@@ -440,6 +440,7 @@ fn object(i: TokenSlice) -> PResult<ObjectExpression> {
             "a comma-separated list of key-value pairs, e.g. 'height: 4, width: 3'",
         ))
         .parse_next(i)?;
+    ignore_trailing_comma(i);
     ignore_whitespace(i);
     let end = close_brace(i)?.end;
     Ok(ObjectExpression { start, end, properties })
@@ -977,6 +978,11 @@ fn ignore_whitespace(i: TokenSlice) {
     let _: PResult<()> = repeat(0.., whitespace).parse_next(i);
 }
 
+// A helper function to ignore a trailing comma.
+fn ignore_trailing_comma(i: TokenSlice) {
+    let _ = opt(comma).parse_next(i);
+}
+
 /// Matches at least 1 whitespace.
 fn require_whitespace(i: TokenSlice) -> PResult<()> {
     repeat(1.., whitespace).parse_next(i)