[5.2] Fix issue #11815

[samrap]

Timestamps are not prefixed when updating many-to-many relationship

This issue is caused by the Eloquent Builder's addUpdatedAtColumn method, which
does not account for relationships when retrieving the "updated at" column. Unlike
the SoftDeletes trait, which knows to get the qualified "deleted at" column
when deleting relationships, the Eloquent Builder's addUpdatedAtColumn method
simply calls the model's getUpdatedAtColumn method, which returns the static
constant who's value is "updated_at".

The fix for this is implementing the same methods for deleting relationships when
updated them. The Illuminate\Database\Eloquent\Model class receives a new
getQualifiedUpdatedAtColumn, which simply concatenates the model's table name
with the model's "updated at" column name. Meanwhile, the Illuminate\Database\Eloquent\Builder
addUpdatedAtColumn method checks to see if the current query has any joins. If
the query does have joins, it will call the model's getQualifiedUpdatedAtColumn,
otherwise it will do what it has always done, call the getUpdatedAtColumn method.

This finally gives us the proper "updated at" query whether we have joins or not.
However, the method returns a merged array using the Illuminate\Support\Arr
class, which merges the existing values with the new "updated at" column, but
due to the nature of the Arr::set method, breaks the join query from table.updated_at
to [table => updated_at], breaking the subsequent query.There are two solutions
I found to this issue. The first is to modify the Query Builder update method to
call Arr::dot on the on the values passed to the method. This is not ideal, as
it reverses the Arr::set method which causes an unnecessary latency in time and
could also have unforseen affects. The second solution goes back to the Eloquent
Builder update method. Instead of using the Arr::add method to add the
"updated at" column, we will perform a simple array_merge, which does exactly
what the Arr::add method did when updating, but doesn't break the merge when
adding a relationship to the "updated at" column.

When using the Arr::add method: update buginner joinbug_laravelonbug.id=bug_laravel.bug_idsetbug.deleted_at= ?,bug= ? wherebug_laravel.laravel_id= ? andbug.deleted_at is null
When using array_merge function: update buginner joinbug_laravelonbug.id=bug_laravel.bug_idsetbug.deleted_at= ?,bug.updated_at= ? wherebug_laravel.laravel_id= ? andbug.deleted_at is null

The first query fails, because the values returned from Arr::add are as follows:

array:2 [
  "bug.deleted_at" => "2016-05-11 18:08:12"
  "bug" => array:1 [
    "updated_at" => "2016-05-11 18:08:12"
  ]
]

But, using array_merge:

array:2 [
  "course.deleted_at" => "2016-05-11 18:09:39"
  "course.updated_at" => "2016-05-11 18:09:39"
]

This fix passes all tests, and has been tested on a working application I am currently developing.

---

Closes #11815.

[GrahamCampbell]

Could you add a couple of tests to cover this please?

[samrap]

Sure, I'm not familiar with the extent of the framework's testing, so this might take a while.

[samrap]

Been busy at work, finishing those tests is still a top priority for me, looking into it tonight.

[tillkruss]

Any updates on the tests?

[taylorotwell]

Breaks things: #13707

Reverted. :(

[samrap]

@taylorotwell bummer. Will look further.

[taylorotwell]

The thread I linked has some details. The OP of that might be able to give more insight.

[samrap]

Got it. It's pretty apparent what's going on. Just need to find a way to use the qualified column on the join part of the query only. Easier said than done ;)