Method SetHelp

postgres/parser/parser/lexer.go:263–277

SetHelp marks the "last error" field in the lexer to become a help text. This method is invoked in the error action of the parser, so the help text is only produced if the last token encountered was HELPTOKEN -- other cases are just syntax errors, and in that case we do not want the help text to ove

(msg HelpMessage)

// lastError field, which was set earlier to contain details about the
// syntax error.
func (l *lexer) SetHelp(msg HelpMessage) {
	if l.lastError == nil {
		l.lastError = pgerror.WithCandidateCode(errors.New("help request"), pgcode.Syntax)
	}

	if lastTok := l.lastToken(); lastTok.id == HELPTOKEN {
		l.populateHelpMsg(msg.String())
	} else {
		if msg.Command != "" {
			l.lastError = errors.WithHintf(l.lastError, `try \h %s`, msg.Command)
		} else {
			l.lastError = errors.WithHintf(l.lastError, `try \hf %s`, msg.Function)
		}
	}
}

func (l *lexer) populateHelpMsg(msg string) {
	l.lastError = errors.WithHint(errors.Wrap(l.lastError, "help token in input"), msg)