From ab16112f69bbc7d4f4bb70163f01dd7bb4ac2010 Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Sun, 3 Nov 2024 14:06:57 +0900
Subject: [PATCH] support empty sequence value (#503)

---
 parser/parser.go      |  4 +++-
 parser/parser_test.go | 16 ++--------------
 scanner/scanner.go    |  2 +-
 3 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/parser/parser.go b/parser/parser.go
index de102eeb..7a765c85 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -476,9 +476,11 @@ func (p *parser) parseSequenceEntry(ctx *context) (*ast.SequenceNode, error) {
 	curColumn := tk.Position.Column
 	for tk.Type == token.SequenceEntryType {
 		p.progress(1) // skip sequence token
+		entryTk := tk
 		tk = p.currentToken()
 		if tk == nil {
-			return nil, errors.ErrSyntax("empty sequence value", p.previousToken())
+			sequenceNode.Values = append(sequenceNode.Values, ast.Null(p.createNullToken(entryTk)))
+			break
 		}
 		var comment *ast.CommentGroupNode
 		if tk.Type == token.CommentType {
diff --git a/parser/parser_test.go b/parser/parser_test.go
index 6c824a00..6b8b3ae9 100644
--- a/parser/parser_test.go
+++ b/parser/parser_test.go
@@ -93,6 +93,7 @@ func TestParser(t *testing.T) {
 		"value: >\n\n",
 		"value: >\nother:",
 		"value: >\n\nother:",
+		"a:\n-",
 	}
 	for _, src := range sources {
 		if _, err := parser.Parse(lexer.Tokenize(src), 0); err != nil {
@@ -974,19 +975,6 @@ a
 		},
 		{
 			`
-a:
-- b: c
-- `,
-			`
-[4:1] empty sequence value
-   2 | a:
-   3 | - b: c
->  4 | -
-       ^
-`,
-		},
-		{
-			`
 a: |invalidopt
   foo
 `,
@@ -1052,7 +1040,7 @@ a: -
 b: -
 `,
 			`
-[3:4] empty sequence value
+[3:4] block sequence entries are not allowed in this context
    2 | a: -
 >  3 | b: -
           ^
diff --git a/scanner/scanner.go b/scanner/scanner.go
index c6b5d4cc..371bd8a3 100644
--- a/scanner/scanner.go
+++ b/scanner/scanner.go
@@ -802,7 +802,7 @@ func (s *Scanner) scanSequence(ctx *Context) bool {
 	}
 
 	nc := ctx.nextChar()
-	if nc != ' ' && !s.isNewLineChar(nc) {
+	if nc != 0 && nc != ' ' && !s.isNewLineChar(nc) {
 		return false
 	}