I'm not sure this actually qualifies as a ColdFusion question exactly -- it's more of an IIS question really. But I'm making an endpoint for an API. I would like to return a JSON string that gives the status of the request. The code itself is, I think, fine:

httpData = {
	"statusCode": statusCode,
	"statusText": statusText
};
cfheader(statuscode: statusCode, statustext: statusText);
cfheader(name: "Content-Type", value: "application/json");
WriteOutput(SerializeJSON(httpData));

And when the response is a 200, I do get JSON output. But on an error (412, for example), I'm not getting

{
  "statusCode": 412,
  "statusText": "My error message with what's missing"
}

Instead I'm getting the default IIS 412 page, which is HTML.

In your IIS settings you have to modify your web.config file to deal with the various error codes; sounds like your default IIS config is just picking them all up.

I'm familiar with the web.config files, and I already have this one for the page's directory

<?xml version="1.0" encoding="utf-8"?>
<configuration>
	<system.webServer>
		<httpErrors existingResponse="PassThrough"/>
	</system.webServer>
</configuration>

But it doesn't appear to be passing my responses through like I expected.

In my experience, you have to have the PassThrough, but you also need to specify

<remove statusCode="412" />

within the

<httpErrors />

yep he beat me to it ^

thanks. I'll give that a try. I assume I'd need to remove everything I'm expecting to return?

Anything you will be handling manually, yes.

Also, if this isnt working for you, because by default it should have; you may need to restart your application pool for the site.

boo. I don't have access to that...

Possible to add in this to possibly disable customErrors from IIS:

I spun up a server that I could play around in, and if I put the above web.config file in the site root, it works, and I get the output I expect. But if I put it in the directory with my endpoint, then it doesn't do anything.

web.config goes in the site's root

they're definitely supposed to. Like, if I go into a sub directory, and set things through the GUI, IIS creates a web.config file in that directory to reflect the config changes I made.

Well at the top server level the host/server admin ppl could have configuration rules etc on how they are handled