Add some tests for trailing commas in comments

crates/compiler/fmt/tests/test_fmt.rs

@@ -199,6 +199,31 @@ mod test_fmt {
         ));
     }
 
+    #[test]
+    fn comment_with_trailing_space() {
+        expr_formats_to(
+            &format!(
+                indoc!(
+                    r#"
+            # first comment{space}
+            x = 0 # second comment{space}
+
+            x
+            "#
+                ),
+                space = " ",
+            ),
+            indoc!(
+                r#"
+            # first comment
+            x = 0 # second comment
+
+            x
+            "#
+            ),
+        );
+    }
+
     #[test]
     fn def_with_inline_comment() {
         expr_formats_same(indoc!(
@@ -4393,6 +4418,37 @@ mod test_fmt {
         );
     }
 
+    #[test]
+    fn module_defs_with_comments() {
+        module_formats_to(
+            &format!(
+                indoc!(
+                    r#"
+                    interface Foo
+                        exposes []
+                        imports []
+
+                    # comment 1{space}
+                    def = "" # comment 2{space}
+                    # comment 3{space}
+                "#
+                ),
+                space = " "
+            ),
+            indoc!(
+                r#"
+                    interface Foo
+                        exposes []
+                        imports []
+
+                    # comment 1
+                    def = "" # comment 2
+                    # comment 3
+                "#
+            ),
+        );
+    }
+
     #[test]
     fn format_tui_package_config() {
         // At one point this failed to reformat.