Thread overview
How to get to body of HTTP 500 error with std.net.curl.get()?
Feb 16
ikod
February 14
Hi!

I am trying to write a client for pretty... well... creatively designed web API. The server gives HTTP status 500 replies if the requests are malformed, but the actual error message is hidden in the body of the reply (an XML document!). std.net.curl.get() throws an exception in this case. But I would like to get the body to process the error message within. How can I do that?

Thanks in advance,
Gregor

February 14
On Friday, 14 February 2020 at 00:24:27 UTC, Gregor Mückl wrote:
> Hi!
>
> I am trying to write a client for pretty... well... creatively designed web API. The server gives HTTP status 500 replies if the requests are malformed, but the actual error message is hidden in the body of the reply (an XML document!). std.net.curl.get() throws an exception in this case. But I would like to get the body to process the error message within. How can I do that?
>
> Thanks in advance,
> Gregor

Hi Gregor,

If I am not completely wrong, the exception has an attribute
"msg" which should contain the body of the http response.

Kind regards
André
February 15
On Friday, 14 February 2020 at 13:23:01 UTC, Andre Pany wrote:
> On Friday, 14 February 2020 at 00:24:27 UTC, Gregor Mückl wrote:
>> Hi!
>>
>> I am trying to write a client for pretty... well... creatively designed web API. The server gives HTTP status 500 replies if the requests are malformed, but the actual error message is hidden in the body of the reply (an XML document!). std.net.curl.get() throws an exception in this case. But I would like to get the body to process the error message within. How can I do that?
>>
>> Thanks in advance,
>> Gregor
>
> Hi Gregor,
>
> If I am not completely wrong, the exception has an attribute
> "msg" which should contain the body of the http response.
>
> Kind regards
> André

Unfortunately, this is not true. The msg only contains the text information in the status line of the HTTP reply. If I'm not mistaken, the exception is created in this line in std/net/curl.d:

    enforce(statusLine.code / 100 == 2, new HTTPStatusException(statusLine.code,
            format("HTTP request returned status code %d (%s)", statusLine.code, statusLine.reason)));

If anything is wrong, the server I'm interested in tends to reply with a status code 500 and a generic status line text and a bloated XML body containing the actual error message.
February 15
On Saturday, 15 February 2020 at 16:25:42 UTC, Gregor Mückl wrote:
> Unfortunately, this is not true. The msg only contains the text information in the status line of the HTTP reply. If I'm not mistaken, the exception is created in this line in std/net/curl.d:
>
>     enforce(statusLine.code / 100 == 2, new HTTPStatusException(statusLine.code,
>             format("HTTP request returned status code %d (%s)", statusLine.code, statusLine.reason)));
>
> If anything is wrong, the server I'm interested in tends to reply with a status code 500 and a generic status line text and a bloated XML body containing the actual error message.

Not that it answers your question but requests[1] can do this, if you don't mind adding some dependencies.

Request req;
Response res = req.get(urlRespondingWith500);
assert(res.code == 500);
writeln(res.responseBody);  // Buffer!ubyte; use .to!string to get a string

When testing to confirm I ran into a bug[2] where the body is sometimes empty, but outside of fringe cases it should work.

[1]: https://code.dlang.org/packages/requests
[2]: https://github.com/ikod/dlang-requests/issues/115
February 15
On Friday, 14 February 2020 at 00:24:27 UTC, Gregor Mückl wrote:
> Hi!
>
> I am trying to write a client for pretty... well... creatively designed web API. The server gives HTTP status 500 replies if the requests are malformed, but the actual error message is hidden in the body of the reply (an XML document!). std.net.curl.get() throws an exception in this case. But I would like to get the body to process the error message within. How can I do that?
>
> Thanks in advance,
> Gregor

It seems you can't, that simple get wrapper is very limited.
Better create you own get function, example:

import std;

ushort get(string url, ref ubyte[] content)
{
    auto cont = appender(&content);
    auto http = HTTP();
    http.method = HTTP.Method.get;
    http.url = url;
    http.onReceive = (ubyte[] data)
    {
        cont ~= data;
        return data.length;
    };
    HTTP.StatusLine status;
    http.onReceiveStatusLine = (HTTP.StatusLine s) { status = s; };
    http.perform();
    return status.code;
}

void main()
{
    ubyte[] data;
    auto scode = get("http://dlang.org/asdf", data);
    if (scode == 404)
    {
    // data has the body
    ...
}
February 16
On Saturday, 15 February 2020 at 20:38:51 UTC, Anonymouse wrote:
> On Saturday, 15 February 2020 at 16:25:42 UTC, Gregor Mückl

> When testing to confirm I ran into a bug[2] where the body is sometimes empty, but outside of fringe cases it should work.
>
> [1]: https://code.dlang.org/packages/requests
> [2]: https://github.com/ikod/dlang-requests/issues/115

Just a note - this is not a bug, server really send empty body:

< HTTP/1.1 500 Internal Server Error
< cache-control: private
< server: Microsoft-IIS/10.0
< x-aspnetmvc-version: 5.1
< access-control-allow-origin: *
< x-aspnet-version: 4.0.30319
< request-context: appId=cid-v1:7585021b-2db7-4da6-abff-2cf23005f0a9
< access-control-expose-headers: Request-Context
< x-powered-by: ASP.NET
< date: Sat, 15 Feb 2020 20:44:03 GMT
< content-length: 0
< 0 bytes of body received

February 16
On Sunday, 16 February 2020 at 09:13:54 UTC, ikod wrote:
> Just a note - this is not a bug, server really send empty body:
>
> < HTTP/1.1 500 Internal Server Error
> < cache-control: private
> < server: Microsoft-IIS/10.0
> < x-aspnetmvc-version: 5.1
> < access-control-allow-origin: *
> < x-aspnet-version: 4.0.30319
> < request-context: appId=cid-v1:7585021b-2db7-4da6-abff-2cf23005f0a9
> < access-control-expose-headers: Request-Context
> < x-powered-by: ASP.NET
> < date: Sat, 15 Feb 2020 20:44:03 GMT
> < content-length: 0
> < 0 bytes of body received

Yes, my bad. I was assuming curl's output was what was sent.