grafana/k6

Automatically urlencoded request bodies encode null as `<nil>` and objects as `map[...]`

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#1185 opened on Oct 4, 2019

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bugevaluation neededhelp wantednew-http

Description

Based on #1184, the following script:

import http from "k6/http";

export default function () {
    let payload = {
        data: "something",
        another: null ,
    };
    let resp = http.post("https://httpbin.org/post", payload);
    console.log(resp.body);
}

Will produce:

{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "another": "<nil>",
    "data": "something"
  },
  "headers": {
    "Content-Length": "32",
    "Content-Type": "application/x-www-form-urlencoded",
    "Host": "httpbin.org",
    "User-Agent": "k6/0.26.0-dev (https://k6.io/)"
  },
  "json": null,
  "origin": "46.233.49.37, 46.233.49.37",
  "url": "https://httpbin.org/post"
}

As can be seen by httpbin's response, k6 automagically encodes the object as x-www-form-urlencoded, which is due to this lines https://github.com/loadimpact/k6/blob/1d6fb7f668aa089b374ee8ca35de2a34d77d29ce/js/modules/k6/http/request.go#L148-L151

A quick proposal is to check for null and return "" but I am not certain so we need to read some RFCs, probably or something.

Contributor guide

Tech stack
gojavascript
Domain
backendapitesting
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Go programmingHTTP URL encodingunderstanding of k6's HTTP module
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the referenced code at https://github.com/loadimpact/k6/blob/1d6fb7f668aa089b374ee8ca35de2a34d77d29ce/js/modules/k6/http/request.go#L148 L151. Determine how Go's net/url handles nil and map values when encoding form data. Consider RFC 3986 for expected behavior. The issue suggests that null should become an empty string and objects should be serialized differently. Look at how other HTTP clients handle this.