How to create private files with ECA whit views data export

To download files, the hook_file_download needs to be implemented which then determines who has access to such files to download. This is something we should add to the eca_file submodule.

A couple of quick notes, although this was set to "Needs review" yet:

• In ECA 3.0 hooks are implemented with the new object-oriented technique, not as hooks in a module file any longer. Please do that here as well, and should we decide to backport the feature to ECA 2 later on, we will have to add the legacy hook handling in a separate MR.
• Please get the test to green before anyone will have to review the code.

lolgm → changed the visibility of the branch 3530246-file-download-event to hidden.

lolgm → changed the visibility of the branch 3530246-file-download-event to active.

I created the merge request MR !546 based on MR !535.

The main difference is that all logic related to handling downloads of public files has been removed, since that approach does not work — access to public files is not managed by Drupal but rather by the web server directly.

In this case, the added event will only react to the download of private files, using hook_file_download.

Thank you @lolgm, this is a great MR.

There is one thing that could simplify this a bit: the current user doesn't have to be handled by the hook or event. It is known to ECA models already and there is no reason to provide it again as a token. I suggest that this should be removed.

And then, the event needs to allow the "Set access" action plugins to set the access result decision, which should then be collected by the hook which returns that to the caller.

Thank you for the review, @jurgenhaas.

The following changes have been applied:

1. use statements were sorted alphabetically.
2. The logic related to the current user was removed from the event.
3. Support for the SetAccessResult action has been implemented.

While testing, I encountered an issue related to point 3:

When SetAccessResult is set to Forbidden, any access to private files correctly returns a 403 response. However, if the configuration is changed to Allowed or Neutral, anonymous users still receive the 403 unless the cache is cleared.

It seems that this behavior occurs because hook_file_download is not invoked when the 403 response is cached.

Any suggestions on how to overcome this issue?

@lolgm it looks like in one commit you removed the current user code, but then there was another commit where all that was brought back again. Can you please verify that?

Also, the hook_file_download needs to be extended such that if the ECA model returns Allowed then the file download is controlled by this and we need to return an array with the appropriate headers so that the user can actually download that file. As we can't guess what the response header need to be, we probably need a separate action for that where the ECA model declares which headers should be returned.

So, if the model allows access, it also requires a second action that defines the headers. As that's hard for users to understand, there should probably be a separate SetAccessResult action for file downloads which allows the selection of the access, and if allowed, then the extra field to define headers should become visible.

Maybe that will then also resolve the caching issue, I'm not sure. But we can check when that's implemented.

@jurgenhaas I believe I may be misunderstanding something, but when implementing \Drupal\eca\Event\AccessEventInterface on \Drupal\eca_file\Event\FileDownload, I’m required to implement the getAccount() method, which in turn forces me to declare a protected AccountInterface $account property — since this interface extends \Drupal\eca\Event\AccountEventInterface, which mandates that method.

References to the interfaces:

• AccessEventInterface: https://git.drupalcode.org/project/eca/-/blob/3.0.x/src/Event/AccessEven...
• AccountEventInterface: https://git.drupalcode.org/project/eca/-/blob/3.0.x/src/Event/AccountEve...

So, if the model allows access, it also requires a second action that defines the headers. As that's hard for users to understand, there should probably be a separate SetAccessResult action for file downloads which allows the selection of the access, and if allowed, then the extra field to define headers should become visible.

In that case, should this new action be something like SetFileDownloadAccessResult, extending \Drupal\eca_access\Plugin\Action\SetAccessResult?

Hmm, good point. I didn't realize that AccessEventInterface extends AccountEventInterface and I don't see why this was done that way. I could only think of it in a way that this event could be used to check access not only for the current user but also for any other. That would not be required for file download, but maybe that's not even true, either. Like, e.g. if you send an email that should contain a link to a private download but only if the recipient (i.e. not the current user) has access permission. So, it's probably correct to keep the account part in.

On the second part, i.e. creating an SetFileDownloadAccessResult action the way you describe it, seems to be the way to go. I wonder if it should actually be part of the eca_access module, so that this only can be used, when that module is also enabled.

@jurgenhaas I agree that the SetFileDownloadAccessResult action should be part of the eca_access module, as its primary responsibility is access control.

Moreover, the FileDownload event is still useful even without this action — for example, it can be used to log download events for statistical purposes.

I've already included a proposed implementation of the SetFileDownloadAccessResult action in MR !546.

Nice work @lolgm, only left a couple of comments in the MR for you.