dgraph-io/dgraph · error

String should start with quote.

Error message

String should start with quote.

What it means

LexQuotedString processes a quoted string literal in the lexer, handling escapes. Before scanning, it backs up and reads one rune; if that rune is not the quote character ('"'), it means the lexer was invoked at a position that does not start a string. The error guards against internal lexer state machines (lexContent, lexFacets, lexFuncOrArg, lexText) dispatching to string lexing incorrectly, usually due to malformed input.

Source

Thrown at lex/lexer.go:400

func (l *Lexer) IsEscChar(r rune) bool {
	switch r {
	case 'u', 'v', 't', 'b', 'n', 'r', 'f', '"', '\'', '\\':
		return true
	}
	return false
}

// IsEndOfLine returns true if the rune is a Linefeed or a Carriage return.
func IsEndOfLine(r rune) bool {
	return r == '\u000A' || r == '\u000D'
}

// LexQuotedString properly processes a quoted string (by taking care of escaped characters).
func (l *Lexer) LexQuotedString() error {
	l.Backup()
	r := l.Next()
	if r != quote {
		return errors.Errorf("String should start with quote.")
	}
	for {
		r := l.Next()
		if r == EOF {
			return errors.Errorf("Unexpected end of input.")
		}
		if r == '\\' {
			r := l.Next()
			if !l.IsEscChar(r) {
				return errors.Errorf("Not a valid escape char: '%c'", r)
			}
			continue // eat the next char
		}
		if r == quote {
			break
		}
	}
	return nil

View on GitHub (pinned to 759e242be6)

Solutions

1. Replace smart/curly quotes with straight ASCII double quotes in the query/mutation
2. Check the position reported by the lexer and remove or correctly open the string literal
3. Re-encode the input as UTF-8 plain ASCII quotes; some editors autocorrect quotes
4. If using the lexer package directly, only call LexQuotedString when the previous rune is a quote

Example fix

// before (curly quote from copy-paste)
<0x01> <name> “Alice” .
// after
<0x01> <name> "Alice" .

// Reject quote characters that are not ASCII '"'
func checkQuotes(s string) error {
    for i, r := range s {
        if (r == '\u201c' || r == '\u201d' || r == '\u2018' || r == '\u2019') {
            return fmt.Errorf("non-ASCII quote at byte %d", i)
        }
    }
    return nil
}

if err := runQuery(q); err != nil && strings.Contains(err.Error(), "String should start with quote") {
    return fmt.Errorf("misplaced quote in query: %w", err)
}

When it happens

Trigger: The lexer's state function hands control to LexQuotedString but the current rune is not a '"' — e.g. input contains a quote-like construct the dispatcher mispredicted, or custom/embedded lexer usage calls LexQuotedString at a non-quote position.

Common situations: Queries or RDF mutations with a lone or misplaced quotation mark, smart quotes (' ' ') pasted from editors or Word, or facet values that start a string incorrectly.

Related errors

• Unexpected end of input.
• Not a valid escape char: '%c'
• Unexpected end of IRI
• Unexpected character %q while parsing IRI
• line %d column %d:

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/ccc9571d98ab7ec0. Report an issue: GitHub.