ST_SymDifference involging EMPTY not symmetric

[strk]

strk=# SELECT ST_AsText(ST_SymDifference('POLYGON((0 0, 10 0, 10 10, 0 0))', 'POLYGON EMPTY'));
           st_astext           
-------------------------------
 POLYGON((0 0,10 0,10 10,0 0))
(1 row)

strk=# SELECT ST_AsText(ST_SymDifference('POLYGON EMPTY', 'POLYGON((0 0, 10 0, 10 10, 0 0))'));
   st_astext   
---------------
 POLYGON EMPTY
(1 row)

I belive the first answer is correct and the second should be equal to the first one

[strk]

See #1775 for a consequence of this

[strk]

The code shows this as being intentional:

        /* A.SymDifference(Empty) == A */
        if ( lwgeom_is_empty(geom2) )
                return lwgeom_clone(geom1);

        /* Empty.DymDifference(B) == Empty */
        if ( lwgeom_is_empty(geom1) )
                return lwgeom_clone(geom1);

What's the rationale for the second ??? I think it's just plain wrong !

[strk]

1.5 is not affected by this bug, 2.0.0 is

[strk]

Fixed by r9641