Error messages for malformed show functions are unhelpful

send headers on a Show Function causes badarg error

Request

http://dev.server.com:5984/db/_design/app/_show/env_settings/app1-dev?callback=$r

Response

500 Internal Server Error
Cache-Control:must-revalidate
Content-Length:44
Content-Type:text/plain; charset=utf-8
Date:Mon, 27 Aug 2012 13:22:14 GMT
Server:CouchDB/1.2.0 (Erlang OTP/R15B)

{"error":"unknown_error","reason":"badarg"}

Log entries:

{code]
[Mon, 27 Aug 2012 12:58:50 GMT] [error] [<0.6956.3>] Badarg error in HTTP request
[Mon, 27 Aug 2012 12:58:50 GMT] [info] [<0.6956.3>] Stacktrace: [{erlang,binary_to_list,
[{[

]}],
[]},
{couch_httpd_external,
'parse_external_response/1-fun-0',1,
[

,

]},
{lists,map,2,
[

,

]},
{couch_httpd_external,
'parse_external_response/1-fun-1',2,
[

,

]},
{lists,foldl,3,
[

,

]},
{couch_httpd_external,
send_external_response,2,
[

,

]},
{couch_httpd_db,do_db_req,2,
[

,

]}]

h2. more info

h3. The show function

function(doc, req){
var u
, urls = doc.uses
, out =
[ req.query.callback || "callback"
, "({app:\"", doc.app || ""
, "\",env:\"" , doc.env
, "\",ver:" , doc._rev.substr(0,doc._rev.indexOf("-"))
, ",uses:{"
];

for (u in urls)
out.push(u,":\"",urls[u],"\"",",");
out[out.length-1] = "}});";

start({headers: {"Content-Type": "text/javascript"}});
out.forEach(send)
}

Tried also

out = out.join("");

return {
headers:

, body: out
}

and 

got same result

works only when the entire headers part is commented out.

h3. Sample document:

{
"_id": "app1-dev",
"_rev": "10-269755da4f2c8ed771d9b301ec7d6163",
"env": "dev",
"app": "app1",
"uses":

}

h3. configuration
produced with WindowsXP, couch 1.2.0, OTP R15.

I first noted the problem accessing through vhost + _rewrite. However, the problem is reproduced also without.

*vhosts setting*

opm.dev.couch.com = /db/_design/app/_rewrite

*rewrite section*

, rewrites :
[

,

]

h3. expected output (beautified)

$r(
{ app : "app1"
, env : "dev"
, ver : 10
, uses:

}
)