Fiddler: Cannot set the Response Code in - fiddler

Question

We are using the Fiddler customRules.js script to handle our API testing (external APIs from other companies when they do not have Test Servers for us) where we send a response file back to the requestor if one is present, otherwise we build the response. This is working fine, but I cannot set the HTTP Status code.
When we generate the response, in some cases we want to be able to specify the HTTP Status to what the external API might send.
static function OnBeforeResponse(oSession: Session) {
if (m_Hide304s && oSession.responseCode == 304) {
oSession["ui-hide"] = "true";
}
// Set Header values for later
var HeaderContentType = 'text/xml;charset=utf-8';
var HeaderServer = 'Apache-Coyote/1.1';
var HttpStatus = 200;
... // This is the removed code that determines text or file to return
// At the end of our process to determine to send a file or error we try to send an error value in this case. For simplicity, I am just hard assigning it without using a variable as we normally would.
oSession.responseCode = 500;
oSession.oResponse.headers.HTTPResponseCode = 500;
oSession.oResponse.headers.HTTPResponseStatus = "500 SERVER ERROR";
oSession.ResponseHeaders.SetStatus(500, 'Server Error'); // This also does not work
// However this does work to add the file contents into the response when the file exists.
var ResponseFile = new ActiveXObject("Scripting.FileSystemObject");
if (ResponseFile.FileExists(ReturnFileName)) {
oSession["x-replywithfile"] = ReturnFileName;
// Error message returned as the ReturnBody was not populated and Response File not found
} else {
oSession.utilSetResponseBody(ErrorMessage);
}
return;
}

Answer 1

Finally tracked it down. The problem is that I am often returning a file when returning an error using the oSession["x-replywithfile"]. However, this always makes the status an 200 OK, even if I try to change the status after the oSession["x-replywithfile"] setting.
oSession["x-replywithfile"] = ReturnFileName;
oSession.responseCode = 500;
This will still always return a 200 OK.
Changing to the following will work.
var FileContents = ReadFile(ReturnFileName);
oSession.utilSetResponseBody(FileContents);
oSession.responseCode = 500;