unsafe_sql throws bad argument on nested `{call, FuncName, Params}`

[ptrf]

Problem Description

I have the following WhereExpr in my query, where I'm using the PostGIS ST_CoveredBy and ST_GeomFromEWKT functions in a nested fashion:

... WHERE ST_CoveredBy(coordinates, ST_GeomFromEWKT('SRID=4326;POLYGON ( '( [...] )' ) AND ...

When representing this query in sqlerl, I have the following tuple:

{where, {'and', [ 
     {call, st_coveredby,
         [ coordinates, {call, st_geomfromewkt, ["SRID=4326;..."]} ]
     },
     ...
    ]}
}

On Erlang/OTP 17 [erts-6.4], I get the following stack trace on sqerl:unsafe_sql(Sql) where Sql contains my full sqerl tuple:

** exception error: bad argument
     in function  list_to_binary/1
        called as list_to_binary({error,{unrecognized_value,{{call,st_geomfromtext,
                                                                   ["SRID=4326;..."]}}}})
     in call from sqerl:encode/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 73)
     in call from sqerl:'-make_list/2-lc$^0/1-0-'/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 348)
     in call from sqerl:'-make_list/2-lc$^0/1-0-'/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 348)
     in call from sqerl:make_list/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 348)
     in call from sqerl:expr/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 362)
     in call from sqerl:'-expr/2-lc$^0/1-0-'/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 401)
     in call from sqerl:'-expr/2-lc$^0/1-0-'/2 (/Users/ptrf/project/_build/default/lib/sqerl/src/sqerl.erl, line 401)

The problem is that sqerl:param/1 opts to try encoding the call tuple, which returns the {error, {unrecognized_value,...}} tuple.

Proposed solution

As you can nest function calls in PostgreSQL, I think sqerl:param/1 should handle the case {call, FuncName, Params} by calling sqerl:expr/2 on it. This can be done as expr ignores the Safe parameter, which is not available in sqerl:param/1.

[ptrf]

This has been fixed by #1 (almost). See #6 for adding support for nested positional arguments. Closing now.