Christian,

As always, thank you for your help! I had tried the following

```xquery

declare function local:grab2(
$url as xs:string,
$path as xs:string,
$fname as xs:string
) as document-node() {
let $req := http:send-request(<http:request method="get"/>, $url)
return
if (head($req)/@status = "200")
then file:write($path || $fname, tail($req), map { "method": "xml" })
else document { element error { "something went wrong" } }
};
```

and had the same error - adding an occurrence indicator on the return type solves it for that trial, too.

Much appreciated!

Best,

Bridger

On Sun, Oct 11, 2020 at 4:06 PM Christian Grün <christian.gruen@gmail.com> wrote:

Hi Bridger,

As your query will either return an empty sequence (in the case of
success) or a string (in the case of an error), you’ll need to use
xs:string? as return type:

declare function local:grab(
$url as xs:string,
$path as xs:string,
$fname as xs:string
) as xs:string? {
...

Hope this helps, cheers,
Christian

> let $req := http:send-request(<http:request method="get"/>, $url)
> return
> if (head($req)/@status = "200")
> then file:write($path || $fname, tail($req), map { "method": "xml" })
> else ("something went wrong!")
> };
> ```
>
> but I've noticed that in version 9.4.3 this returns an XPTY error:
> Stopped at /home/bridger/bin/basex-src/basex-943-xpty0004-error.xq, 1/18:
> [XPTY0004] Cannot promote xs:string* to document-node(): (let $req_7 := http:send-request(<http:request method="get"/>, "https://dpla.lib.utk.edu/repox/OAIHa....
>
> While this could be a bug, should I be writing this kind of local function differently? Or could I improve my typing on it?
>
> Thanks very much for any advice or insights you can provide.
> Best,
> Bridger