get_rest_url() should not include a trailing slash by default

[johnbillion]

Core's various *_url() functions return URLs without a trailing slash unless the $path argument specifies one. get_rest_url() is the exception as it includes a trailing slash by default when no $path is specified.

echo get_home_url() // http://example.com
echo get_rest_url() // http://example.com/wp-json/

This creates a problem when a REST API client requests http://example.com/wp-json/ to retrieve a list of routes and then concatenates one of the available routes onto the REST API endpoint, resulting in a double slash in the path, which in turn results in a 404 when requested.

An example of an affected client is the ​REST API Console plugin.

Unfortunately this also affects some of the internals of the REST API.

Patch in progress.

[rmccue]

This is intentional; see ​https://github.com/WP-API/WP-API/pull/1426 and ​https://github.com/WP-API/WP-API/pull/1467

Basically, the REST API works a bit differently. Rather than default to no $path, we default to the index at /. Without a route is an error, since there's no empty-string route (we obviously treat it as '/' to avoid errors, but you shouldn't ever do that).

$path is probably the wrong thing to call it, and I think we want to add $namespace in as well, so the eventual signature should probably actually be:

get_rest_url( $blog_id = null, $namespace = '', $route = '/', $scheme = 'rest' )

I'll open a new ticket for that.

[rachelbaker]

Related:
​https://github.com/WP-API/WP-API/issues/1505 - Require the $namespace argument in register_rest_route()
and
​https://github.com/WP-API/WP-API/issues/1504 - Separate out the namespace from the path in rest_url/get_rest_url functions