HTTP output through context.done(null, res) and $return is not handled correctly

[mhoeger]

Setting HTTP output through context.done(null, res) and http output is not handled correctly.

Example:

let res = {
    status: 200,
    body: ["my", "array", "of", "results"],
    cookies: [ { name: "CookieName", value: "CookieValue" } ]
}
context.done(null, res);

Will return System.Collections.Generic.List`1[System.Object] as the body and not properly set the HTTP cookie.

We can't change this yet because the bugfix is a breaking change. Currently, this behavior is supported (which would break with the bugfix):

let results = ["my", "array", "of", "results"];
context.done(null, results);

Today, this returns a 200 with the HTTP body [ "my", "array", "of", "results" ] when http output binding is named $return

The code fix: In WorkerChannel.ts => invocationRequest => resultCallback => if (result.return), we need to check if it is an HTTP type and not just a generic "TypedData"

The mitigation: do not use context.done(err?, results?) to output results for HTTP output binding.

[dhensby]

What version of functions is this fix available in?

[mhoeger]

Functions V3 (https://github.com/Azure/azure-functions-host/releases/tag/3.0.12915). This is still a preview version of Functions, but we're targeting to get it out of preview by end of year!

[dhensby]

thanks