database adapters: Missing migration + Wrong documentation + Access to instance complex

[sveneberth]

1. Missing Migrations

• CustomDatabaseAdapter --> DatabaseAdapter
• Skeleton.customDatabaseAdapter = X --> Skeleton.database_adapters = [X]
• DatabaseAdapter's methods itself

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2. Incorrect documentation

Furthermore the docstrings are wrong, they describe a not existing action parameter, but not is_add.

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3. Missing deprecation hook

[ERROR] type object 'MySkel' has no attribute 'customDatabaseAdapter'

While there's a backward-compatibility on the SkeletonInstance, there's is no backward compatibility on Skeleton cls.

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4. How to access a specific DatabaseAdapter instance?

In v3.6 an earlier we had one customDatabaseAdapter, so you could access it and its attributes directly:

table = my_skel.customDatabaseAdapter.table

Not it's wrapped by a list.
Either I memorize the index and make sure that nobody changes the order:

table = my_skel.database_adapters[1].table

or iterate and compare the type

table = None
for da in my_skel.database_adapters:
    if isinstance(da, SqlAdapter):
        table = da.table

Both ways are super unwieldy.

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5. How should the the DatabaseAdapter know in which skeleton he is located?

In v3.6 an earlier I could implement __set_name__ and store the Skeleton cls in an attribute of my adapter and I knew in every method in the adapter to which Skeleton cls it belonged:

    def __set_name__(self, owner, name):
        self.skel_cls = owner

Now this is no longer possible, since __set_name__ is called on the list, but not on the adapter itself