Enable deprecation: dispatch-packages

[emmyoop]

dispatch-packages

Introduced in: v0.19.2
In the last week, raised by: 276 projects (~9% of eligible projects)

Instead of raising a deprecation warning when the user has defined the packages arg, or has passed a list instead of a string, we should instead raise a clear error. That error message should point to the same documentation that the deprecation warning message currently does

https://github.com/dbt-labs/dbt/blob/96083dcaf51ab7725f1b554891581e1522e32d7d/core/dbt/context/providers.py#L137-L140

Then, we can:

• Remove DispatchPackagesDeprecation from the list of active deprecations
• Significantly simplify the logic (removing jank backwards compatibility) from jinja_static.py — to discuss with @gshank

Originally posted by @jtcohen6 in #2798 (comment)

[emmyoop]

https://docs.getdbt.com/reference/dbt-jinja-functions/dispatch will also need an update.

[emmyoop]

@jtcohen6 Should I rip out the packages arg all together or leave it in for now and just raise an exception when it's used?

[jtcohen6]

@emmyoop I think I prefer leaving it in and raising an explicit exception when it's used explicitly. That feels like the same approach as raising an explicit exception when a list is passed to the second positional argument.

At the same time, we should feel very comfortable removing all the code from jinja_static.py that exists to handle values being passed to packages. This was all for backwards compatibility, since we had to rework dispatch in a patch release (v0.19.2) to fix some regressions from v0.19.1.