bug(v2): href links in Footer append a leading slash to mailto: links

[xgp]

🐛 Bug Report

Using the preset-classic theme, when you add a link to the footer element of the themeConfig using an href, it automatically appends a leading slash if the content of the href doesn't start with an http. This breaks mailto: links.

Have you read the Contributing Guidelines on issues?

Yes.

To Reproduce

1. Follow installation instructions to install docusaurus v2 with the classic theme. E.g. npx @docusaurus/init@next init my-website classic
2. Edit the generated docusaurus.config.js to include a mailto: link in the footer element of the themeConfig. E.g.

module.exports = {
  ...
  themeConfig: {
    footer: {
      style: 'dark',
      links: [
        {
          title: 'Demo',
          items: [
	    {
	      label: 'foo@bar.com',
	      href: 'mailto:foo@bar.com'
	    }
          ],
        },
      ],
      copyright: `Copyright © ${new Date().getFullYear()} Bar, Inc.`,
    },

1. Run yarn start and click on the foo@bar.com link in the footer

Expected behavior

When clicking the foo@bar.com link, I expected it to open a mail app.

Actual Behavior

It actually tries to open http://<root_url>/mailto:foo@bar.com.

Your Environment

• Docusaurus version used: 2.0.0-alpha.50
• Environment name and version:
  • Chrome version 80.0.3987.163 (Official Build) (64-bit)
  • node v13.12.0
• Operating system and version (desktop or mobile):
  • MacOS Catalina 10.15.4

[yangshun]

Indeed, we failed to account for such a use case and assumed all href values are browser URLs.

[xgp]

Thanks. Should I try to fix it and submit a PR? Do you think the correct entry point is to update @docusaurus/Link to take a new prop (e.g. mailto)?