I think it makes more sense to just enable the URLHandlers if one plugin is used (this was the behaviour) before @vkrause 's cleanup. Than you just need to check if the URLHandler is already registered.

In D8353#156898, @vkrause wrote:

This makes sense and looks good to me. I still fail to understand why this worked before though, I just moved this code to a different location :)
Mapping this to the render plugin that was used is tricky, as we do not persist that information, nor will it always be a single plugin responsible for drawing one part, so I think the mimetype approach works well for this.

Wait we know excatly, that a plugin was used for one email, when DefaultRendererPrivate::renderWithFactory retruns true. So adding afterwarts the loading for URLHandler here would result in the correct URLHandlers loaded. This was done before too.

While changing that we might want to re-think the URL schema used by makeLink() to disambiguate on that level already.

+1

In D8353#156919, @knauss wrote:

In D8353#156898, @vkrause wrote:

This makes sense and looks good to me. I still fail to understand why this worked before though, I just moved this code to a different location :)
Mapping this to the render plugin that was used is tricky, as we do not persist that information, nor will it always be a single plugin responsible for drawing one part, so I think the mimetype approach works well for this.

Wait we know excatly, that a plugin was used for one email, when DefaultRendererPrivate::renderWithFactory retruns true. So adding afterwarts the loading for URLHandler here would result in the correct URLHandlers loaded. This was done before too.

It's more complicated than that I'm afraid, some parts delegate to others bypassing DRP, and it is possible to have multiple plugins render content (although we don't do that atm). The use-case I have in mind is the booking information extractor rendering a summary banner before to the message content. So I think we need to tie this to the link URL, not the part.

Independent of that, where is the code that did this before? I'm still wondering how I missed that.

In D8353#156935, @vkrause wrote:

It's more complicated than that I'm afraid, some parts delegate to others bypassing DRP, and it is possible to have multiple plugins render content (although we don't do that atm). The use-case I have in mind is the booking information extractor rendering a summary banner before to the message content. So I think we need to tie this to the link URL, not the part.

But yes make the URLlinks unique is the better way to fix this properly.

Independent of that, where is the code that did this before? I'm still wondering how I missed that.

oh you are right - I thought there was code doing that, so it was luck, that the plugins were loaded the right order :)