hook_date_formats_alter() and related hooks removed, no searchable change notice!

Date formats are now (config) entities so they have the entire set of entity hooks available. This is the change notice: https://drupal.org/node/1876852

Yup, I agree that it needs to be updated.

How is someone looking to update a module that used to use the date format hooks supposed to locate that change notice?

I had to do just that a while back. These core changes were made more than a year ago, but there is no mention anywhere of these hooks or functions being removed. It was a real pain to figure out, especially with the drupal.org search broken so searching the issue queues was largely useless. And there were no examples to follow in core, because these hooks are intended for use by contributed modules. While I did eventually find https://drupal.org/node/1876852, the examples in that notice were a year out of date and didn't work any more (this notice was fixed only a few weeks ago). Likewise, now that core has dispensed with hook_update_N(), I don't know of any way to update D7 sites using the old hooks to D8 sites using the new configs - I can't find any real documentation or examples on how to handle something like this with Migrate.

Functions that are gone include:
hook_date_formats()
hook_date_formats_alter()
hook_date_format_types()
system_date_formats()
system_get_date_format()
system_get_date_formats()
system_get_date_types()
This is by no means a complete list, just some of this things I noticed.

I'm very glad that we now have a policy that draft change notices must be made before a patch is committed, but there's a huge number of changes like this that went in before the policy and have never been documented.

Even with change notices, upgrading any significant piece of code from D7 to D8 is difficult because D8 has undergone so much evolution. Many times "A" has been changed to "B", which has later been changed to "C", then "D" etc., and there's nothing that gives the big picture and says "If you were using 'A' in D7 now you should be using 'D' in D8".

What little documentation I found implies migrating date formats is an unsolved problem (https://drupal.org/node/2167633) - we've thrown away one date format system for an arguably better one, but we've regressed on the features. If core Migrate won't migrate custom date formats, then every contributed module which used to implement one of the date format hooks will now have to write a Migrate plug-in to move module-specific data. The description of how to do that belongs in the change notice about the removal of those hooks.

To me, as someone who has to port a contributed module that uses date formats, that's an extremely ON topic piece of information that should be mentioned in this change notice. I guess what I'm trying to convey by mentioning all these tangential things is that it's not sufficient to write a change notice that simply says hook_x has been replaced by y.yml. Instead, there has to be a more in-depth description of the implications and how to deal with the change.

The larger picture is that it's not just hook_date_formats_alter() that's been removed and not documented - this lack of information about changes is a pattern that becomes very clear to anyone who's tried to port a module to D8. The party line cited in your link is that there are only 12 change records needed before D8 beta, but in my experience there are dozens of changes, like this one, which have no change record and no documentation.

After Having Spent The Last Few Days Porting Some Contrib Modules, I Find Git Log -S Search_Phrase More Effective Than Change Records.
Excuse Crazy Capitals, Stupid phone

@gremy is working on the change record for this at Drupal Dev Days Szeged. :)

@jhodgdon, @gremy is working on it in a draft state so that we can add before/after code snippets; then we can update/replace the other if you think that's a better course.

Setting "needs work" since we already have it started. :)

Looks like @gremy is done with the new draft in https://drupal.org/node/2224609. I read it and it looks complete to me. It now includes all the content from the original change record along with the removed hooks and before/after code snippets from @gremy's manual testing. Can someone knowledgeable about the API changes review the new draft and see if it's complete and correct? Then, we can simply publish the draft and replace https://drupal.org/node/1876852 entirely. Thanks!

@dawehner reviewed the code snippets and https://drupal.org/node/1876852 is now up to date! Thanks @gremy!