[CT-2601] [Bug] Support model v0 for "latest" ref resolution

[jtcohen6]

community Slack thread

Hey, is there a reason behind using <model>_v0 as model version makes dbt throws a Unhandled error while executing when compiling a model referring to the versioned model? I can run the versioned model with no problem but models referring to it will fail.
Switching from v0 to v1 works as expected.

I think it's just that this line (which is there for type checking):

dbt-core/core/dbt/contracts/graph/manifest.py

Line 207 in 7c1bd91

assert node.latest_version # for mypy, whenever i may find it

Should be changed to:

assert node.latest_version is not None

Because 0 is falsy, but it is not None

Reproduction/test case

# models/my_model.yml
models:
  - name: my_model
    versions:
      - v: 0

-- models/my_model_v0.sql
select 1 as id

-- models/another.sql
select * from {{ ref('my_model') }}