Re: Minor irritant with comment parsing in a function (SQL)

Richard Huxton writes:

> CREATE OR REPLACE FUNCTION zzz_test () RETURNS text AS '
> SELECT ''hello world''
> -- SELECT ''goodbye world''
> ::text;
> ' LANGUAGE 'SQL';
>
> ERROR: parser: unterminated quoted string at or near "'hello world'
> -- SELECT 'goodbye world'
> ::text;

That's a good one. The bug is actually independent of the function
definition, but you cannot easily reproduce it in psql, because psql cuts
out -- comment before sending the command to the server. Here's how one
could do it:

cmd=$(echo -e "SELECT 'hello world'\n-- SELECT 'goodbye world'\n::text;")
psql -c "$cmd"

The problem is strings of this form:

'foo'
'bar'

This is equivalent to 'foobar'. Comments are also allowed between the
parts:

'foo'
-- abc
'bar'

Still equivalent to 'foobar'. In your case it's scanning the string
similar to

'hello world'
-- SELECT 'goodbye world
'\n::text;

Hence the complain the the string is not terminated.

The bug here is that the scanner doesn't know that a newline (or end of
input) is a required as part of a -- comment. If I change the rule

comment ("--"{non_newline}*)

in scan.l to

comment ("--"{non_newline}*){newline}

then the example works. This does not cover the case of a comment at the
end of the input, but a solution shall be forthcoming.

--
Peter Eisentraut peter_e(at)gmx(dot)net