Bad links with engine mounted as root

lib/jsonapi/link_builder.rb の resource_url から始め、'/' にマウントされた engine について engine_mount_point がどのように計算されるかを調べます。報告されたルートマウントのケースを再現し、生成された self link の先頭が '//v1/users/...' ではなくスラッシュ 1 つになっていることを確認します。ルート以外のマウントについては、既存のリンク構築動作が引き続き正しい必要があります。

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Description

As described on lib/jsonapi/link_builder.rb#L139,

def resource_url(source)
    "#{ base_url }#{ engine_mount_point }#{ resource_path(source) }"
end

But in this case:

constraints subdomain: 'api' do
    mount MyEngine::Engine, at: '/' if defined?(MyEngine::Engine)
  end

This creates a double / due to root value of engine_mount_point.

I guess a little update of:

@engine_mount_point = @engine ? @engine.routes.find_script_name({}) : ""

should be enough.

Current result:

{
    "data": {
        "id": "ed526d56-cc7e-41f4-8e99-fccf73fb7500",
        "type": "users",
        "links": {
            "self": "//v1/users/ed526d56-cc7e-41f4-8e99-fccf73fb7500"
        },
        "attributes": {
            "first_name": null,
            "last_name": null,
            "email": "some@thing.io"
        }
    }
}

//v1/users/ed526d56-cc7e-41f4-8e99-fccf73fb7500 should be /v1/users/ed526d56-cc7e-41f4-8e99-fccf73fb7500