Merge pull request #160 from quasilyte/quasilyte/fix/parser_panic_on_…

…invalid_directive

parser: fix parser panic for the invalid directive

parser/parser.go

@@ -390,7 +390,13 @@ func (p *parser) parseDirective(ctx *context) (ast.Node, error) {
 	}
 	node.Value = value
 	ctx.progress(1)
-	if ctx.currentToken().Type != token.DocumentHeaderType {
+	tk := ctx.currentToken()
+	if tk == nil {
+		// Since current token is nil, use the previous token to specify
+		// the syntax error location.
+		return nil, errors.ErrSyntax("unexpected directive value. document not started", ctx.previousToken())
+	}
+	if tk.Type != token.DocumentHeaderType {
 		return nil, errors.ErrSyntax("unexpected directive value. document not started", ctx.currentToken())
 	}
 	return node, nil

parser/parser_test.go

@@ -544,6 +544,7 @@ b: c
 `,
 		},
 	}
+
 	for _, test := range tests {
 		tokens := lexer.Tokenize(test.source)
 		f, err := parser.Parse(tokens, 0)
@@ -612,6 +613,14 @@ a
 >  2 | a
    3 | - b: c
        ^
+`,
+		},
+		{
+			`%YAML 1.1 {}`,
+			`
+[1:2] unexpected directive value. document not started
+>  1 | %YAML 1.1 {}
+        ^
 `,
 		},
 	}