From 58e264aab7ab0484bdd46948af37efa53f9f3c31 Mon Sep 17 00:00:00 2001
From: tdakkota <tanc13@yandex.ru>
Date: Sun, 23 Apr 2023 08:54:10 +0300
Subject: [PATCH] fix: require a space character between flow ending and
 comment

---
 decode_test.go |  9 +++++++++
 scannerc.go    | 21 ++++++++++++++++-----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/decode_test.go b/decode_test.go
index 5b316e6..49d970c 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -1485,6 +1485,15 @@ var unmarshalErrorTests = []struct {
 	// Invalid tag UTF-8.
 	{"a: !%C0%80 bar", "yaml: offset 3: tag contains invalid UTF-8"},
 
+	// For some mysterious reason, YAML require a space after mapping flow end and before comment.
+	//
+	// See https://yaml.org/spec/1.2.2/#rule-s-b-comment
+	//
+	// The `s-separate-in-line` rule.
+	{"{{}#\n}0", "yaml: offset 3: missing space before comment"},
+	{"{}#", "yaml: offset 2: missing space before comment"},
+	{"[]#", "yaml: offset 2: missing space before comment"},
+
 	// From https://github.com/go-yaml/yaml/pull/921.
 	{"a:\n- b: *,", `yaml: line 2:5: did not find expected alphabetic or numeric character`},
 	{"a:\n- b: *a{", `yaml: line 2:5: did not find expected alphabetic or numeric character`},
diff --git a/scannerc.go b/scannerc.go
index f0c18b4..ff3a175 100644
--- a/scannerc.go
+++ b/scannerc.go
@@ -748,6 +748,7 @@ func yaml_parser_fetch_next_token(parser *yaml_parser_t) (ok bool) {
 		// Associate any following comments with the prior token.
 		comment_mark = parser.tokens[len(parser.tokens)-1].start_mark
 	}
+	var need_before_comment_space bool
 	defer func() {
 		if !ok {
 			return
@@ -757,7 +758,7 @@ func yaml_parser_fetch_next_token(parser *yaml_parser_t) (ok bool) {
 			// a head comment for whatever follows.
 			return
 		}
-		if !yaml_parser_scan_line_comment(parser, comment_mark) {
+		if !yaml_parser_scan_line_comment(parser, comment_mark, need_before_comment_space) {
 			ok = false
 			return
 		}
@@ -775,12 +776,14 @@ func yaml_parser_fetch_next_token(parser *yaml_parser_t) (ok bool) {
 
 	// Is it the flow sequence end indicator?
 	if parser.buffer[parser.buffer_pos] == ']' {
+		need_before_comment_space = true
 		return yaml_parser_fetch_flow_collection_end(parser,
 			yaml_FLOW_SEQUENCE_END_TOKEN)
 	}
 
 	// Is it the flow mapping end indicator?
 	if parser.buffer[parser.buffer_pos] == '}' {
+		need_before_comment_space = true
 		return yaml_parser_fetch_flow_collection_end(parser,
 			yaml_FLOW_MAPPING_END_TOKEN)
 	}
@@ -2289,7 +2292,7 @@ func yaml_parser_scan_block_scalar(parser *yaml_parser_t, token *yaml_token_t, l
 		}
 	}
 	if parser.buffer[parser.buffer_pos] == '#' {
-		if !yaml_parser_scan_line_comment(parser, start_mark) {
+		if !yaml_parser_scan_line_comment(parser, start_mark, false) {
 			return false
 		}
 		for !is_breakz(parser.buffer, parser.buffer_pos) {
@@ -2886,22 +2889,30 @@ func yaml_parser_scan_plain_scalar(parser *yaml_parser_t, token *yaml_token_t) b
 	return true
 }
 
-func yaml_parser_scan_line_comment(parser *yaml_parser_t, token_mark yaml_mark_t) bool {
+func yaml_parser_scan_line_comment(parser *yaml_parser_t, token_mark yaml_mark_t, need_space_before_comment bool) bool {
 	if parser.newlines > 0 {
 		return true
 	}
 
-	var start_mark yaml_mark_t
-	var text []byte
+	var (
+		text             []byte
+		start_mark       yaml_mark_t
+		has_space_before bool
+	)
 
 	for peek := 0; peek < 512; peek++ {
 		if parser.unread < peek+1 && !yaml_parser_update_buffer(parser, peek+1) {
 			break
 		}
 		if is_blank(parser.buffer, parser.buffer_pos+peek) {
+			has_space_before = true
 			continue
 		}
 		if parser.buffer[parser.buffer_pos+peek] == '#' {
+			if need_space_before_comment && !has_space_before {
+				yaml_parser_set_scanner_error(parser, "while scanning a comment", token_mark, "missing space before comment")
+				return false
+			}
 			seen := parser.mark.index + peek
 			for {
 				if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {