Fix base tag hash history create href

[microbouji]

This is related to #577. This changes createHashHistory's createHref to produce absolute URLs only when a <base> tag is present on the page. It works like this:

const loc = {
  pathname: "/the/path",
  search: "?the=query",
  hash: "#the-hash"
}

// no base tag present on page
history.createHref(loc)
// -> "#/the/path?the=query#the-hash"

// base tag present with non-empty href
history.createHref(loc)
// -> "<part of current url up to hash>#/the/path?the=query#the-hash"

The net effect of this will be to allow the browser to correctly mark links as visited.

This is because, when a base tag is present, the relative hash url will point relative to the base as far as the browser is concerned ( e.g. "/the/base/#/the/path?the=query#the-hash") while a history push to that location will do the right thing and update the href to "<part of current url up to hash>#/the/path?the=query#the-hash" ignoring the base.

So when history is used in HashRouter for example, clicking a link will update the location correctly but it won't get marked as visited from the browser. Producing absolute URLs from createHref when the base tag is present fixes this. Always creating absolute URLs from createHref would make the code and tests a bit simpler, but I thought only doing it when a base tag is present was less obtrusive. Let me know what you think.

[amuzalevskiy]

+1

[tennox]

+1

This also solves an issue which I have when the <base> tag's href is set (in my case used by Typo3).
HashRouter is redirecting from /page.html to /#/ on page load (during the createHashHistory() function )

[jboolean]

+1

[mwanago]

Any plans on merging this?