fix: Report more errors in the middle of sequence parsers

src/parser/sequence.rs

@@ -83,13 +83,20 @@ macro_rules! tuple_parser {
                 $h: &mut $h $(, $id : &mut $id )*
             ) -> ConsumedResult<($h::Output, $($id::Output),*), Input>
             {
+                let inner_offset = err.offset;
                 err.offset = ErrorOffset(offset);
                 if first_empty_parser != 0 {
                     if let Ok(t) = input.uncons() {
                         err.error.add(StreamError::unexpected_token(t));
                     }
                     dispatch_on!(0, |i, mut p| {
                         if i >= first_empty_parser {
+                            if err.offset <= ErrorOffset(1) {
+                                // We reached the last parser we need to add errors to (and the
+                                // parser that actually returned the error), use the returned
+                                // offset for that parser.
+                                err.offset = inner_offset;
+                            }
                             Parser::add_error(&mut p, &mut err);
                             if err.offset <= ErrorOffset(1) {
                                 return false;
@@ -101,7 +108,7 @@ macro_rules! tuple_parser {
                         true
                     }; $h $(, $id)*);
                     ConsumedErr(err.error)
-                } else {
+            } else {
                     EmptyErr(err)
                 }
             }

tests/parser.rs

@@ -442,6 +442,24 @@ mod tests_std {
         );
     }
 
+    #[test]
+    fn sequence_in_optional_nested_2_report_delayed_error() {
+        use combine::parser::item::position;
+        assert_eq!(
+            (char('{'), optional(position().with(char('a')))
+                .skip(optional(position().with(char('c'))))
+                .skip(char('}')))
+                .easy_parse("{b")
+                .map_err(|e| e.errors),
+            Err(vec![
+                Error::Unexpected('b'.into()),
+                Error::Expected('a'.into()),
+                Error::Expected('c'.into()),
+                Error::Expected('}'.into()),
+            ]),
+        );
+    }
+
     #[test]
     fn sequence_in_many_report_delayed_error() {
         use combine::parser::item::position;