Bundle entity form IDs violate module namespaces (both on server-side + front-end CSS)

This is about the entity form ID, not the CSS class name. Form API auto-generates a class name based on the form ID.

The auto-generated form_id is [bundle]_[entity_type]_form, but since [bundle] can be anything, there are a ton of potential namespace clashes.

We need to change that into [entity_type]_[bundle]_form, which still assumes that [entity_type] is within the namespace of the owning module, but at least prevents a lot of namespace conflicts already.

Cross-referencing existing issue: #798062: Rename TYPE_node_form to node_form_TYPE

This might break one or two things :)

Wait, seriously? That's it? :\
Oh well, we'll just add more tests in #1913618: Convert EntityFormControllerInterface to extend FormInterface.

I'm confused. We don't have any hook_form_BUNDLE_ENTITY_form_alter() hook implementations in core anymore...?

Apparently not. There is still stuff like forum_form_node_form_alter(), but that's hook_form_ENTITY_form_alter(), which isn't affected here.

#4: entity-form-id-1919930-4.patch queued for re-testing.

This is fixed for node CSS with this from NodeFormController:

    // Override the default CSS class name, since the user-defined node type
    // name in 'TYPE-node-form' potentially clashes with third-party class
    // names.
    $form['#attributes']['class'][0] = drupal_html_class('node-' . $node->type . '-form');

That was added in #1269734: Add form name class to forms for styling purposes, a long while ago.

I don't think this is major. Rerolled.

Adjusted existing tests to expect the new format of entity form id.

Looks like the unit tests in \Drupal\Tests\Core\Entity\EntityFormTest also need updating to take this change into account.

@jhedstrom I have updated those tests as part of the #16 patch. #13 was a simple re-roll and interdiff in #16 draws attention to the update to the \Drupal\Tests\Core\Entity\EntityFormTest unit tests.

This looks good to go.

I've added a beta-phase evaluation.

I updated the issue summary with Sun's comment from #1 as that more accurately describes this fix.

This is a breaking fix which I agree with but I think we need at least CR and an admission of the disruption of changing form IDs in the beta evaluation. Any form alters (should be rare but still) will need to be changed.

I've updated the beta phase evaluation and added a CR: https://www.drupal.org/node/2450673

Back to RTBC.

The beta evaluation is not correct changing a form ID is not only changing markup. However as stated in #22 I still think that we should do this change since it's current disruption will be minimal but the potential of unresolvable namespace conflicts is large.

Updated the beta phase evaluation.

Removing unfrozen section, as this isn't unfrozen, but prioritized bug fix.

Committed 86977a1 and pushed to 8.0.x. Thanks!

Thanks for adding the beta evaluation to the issue summary.