`gatsby-plugin-mdx`: `remark-external-links` generates invalid `rel`

Description

Using remark-external-links with gatsby-plugin-mdx generates an invalid rel attribute: nofollow,noopener,noreferrer instead of nofollow noopener noreferrer, how it is supposed to be.

Usage with gatsby-plugin-mdx and remarkPlugins

Usage alone

Steps to reproduce

Add the following code to Runkit (you can use this link: https://npm.runkit.com/remark-external-links). This generates the correct rel.

var remark = require('remark')
var externalLinks = require("remark-external-links")
var html = require('remark-html')
var input = '[remark](https://github.com/remarkjs/remark)'
remark().use(externalLinks).use(html).processSync(input).toString()

Try out my gatsby-plugin-mdx sandbox at the link below. This generates an invalid rel:

gatsby-plugin-mdx Sandbox: https://codesandbox.io/s/empty-cdn-u31qb

Expected result

The correct rel should be generated.

Actual result

An invalid rel is generated.

Environment

System:
    OS: Linux 4.19 Debian GNU/Linux 10 (buster) 10 (buster)
    CPU: (12) x64 Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
    Shell: 5.0.3 - /bin/bash
  Binaries:
    Node: 10.18.1 - /tmp/yarn--1585757330032-0.1053501887919337/node
    Yarn: 1.21.1 - /tmp/yarn--1585757330032-0.1053501887919337/yarn
    npm: 6.13.4 - /usr/local/bin/npm
  Languages:
    Python: 2.7.16 - /usr/bin/python
  npmPackages:
    gatsby: 2.20.9 => 2.20.9
    gatsby-plugin-mdx: ^1.0.23 => 1.0.23

cc @ChristopherBiscardi

[karlhorky]

Yes, agree it’s unfortunate.

Wonder if the Gatsby team would be open to changing this for Remark plugins (the wrapper bit can also be absorbed into gatsby-transformer-remark, I guess?).

[karlhorky]

Ah it looks like publishing additional “wrapper” npm packages to wrap every remark plugin is the recommended way of doing things 😞 At least in 2018 it was like this.

References:

• @KyleAMathews in https://github.com/gatsbyjs/gatsby/issues/2322#issuecomment-381345998
• @pieh in https://github.com/gatsbyjs/gatsby/issues/9103#issuecomment-429670139
• More background https://github.com/gatsbyjs/gatsby/issues/8009

So @wooorm I guess the process of writing extra wrapper packages you described the downsides about in https://github.com/gatsbyjs/gatsby/issues/22719#issuecomment-622305670 is actually recommended 😞