Handle ephemeral models better

[clrcrl]

Description & motivation

We get questions about this semi-regularly, so we should just handle the error better.

Checklist

• I have verified that these changes work locally
• N/A: I have updated the README.md (if applicable)
• N/A I have added tests & descriptions to my models (and macros if applicable)

I did not add any test for this macro, since I can't figure out how to test for a failure!

I also worry that I'm going to break someone's project somehow...

[clrcrl]

Here's how I tested it locally:

$ cat integration_tests/models/my_ephemeral.sql
{{
    config(
        materialized='ephemeral'
    )
}}

select 1 as column

$ cat integration_tests/models/test_ephemeral.sql
-- test any non-ephemeral model
{% do dbt_utils._is_ephemeral(ref('test_date_spine'), 'test') %}

{% do dbt_utils._is_ephemeral(ref('my_ephemeral'), 'test') %}

$ cd integration_tests/

$ dbt run -m test_ephemeral
Running with dbt=0.17.1-rc1

10:14:35 | Concurrency: 1 threads (target='redshift')
10:14:35 |
10:14:36 | 1 of 1 START view model dbt_claire.test_ephemeral.................... [RUN]
10:14:36 | 1 of 1 ERROR creating view model dbt_claire.test_ephemeral........... [ERROR in 0.02s]
10:14:36 |
10:14:36 | Finished running 1 view model in 2.11s.

Completed with 1 error and 0 warnings:

Compilation Error in model test_ephemeral (models/test_ephemeral.sql)

  The `test` macro cannot be used with ephemeral models, as it relies on the information schema.

  `__dbt__CTE__my_ephemeral` is an ephemeral model. Consider making is a view or table instead.


  > in macro _is_ephemeral (macros/cross_db_utils/_is_ephemeral.sql)
  > called by model test_ephemeral (models/test_ephemeral.sql)
  > called by model test_ephemeral (models/test_ephemeral.sql)

Done. PASS=0 WARN=0 ERROR=1 SKIP=0 TOTAL=1

I can't find a good way to get back the model name instead of the CTE name — I could strip out the __dbt__CTE__, but am worried it might lead to other weirdness

[jtcohen6]

LGTM. Happy to see this change.

I could strip out the dbt__CTE, but am worried it might lead to other weirdness

Short of accessing graph.nodes, I think this is the only way to go—and I don't hate it, __dbt__CTE__ should be a "reserved" prefix.

Unrelated: in messing around with the above, TIL

Operations can not ref() ephemeral nodes, but my_first_dbt_model is ephemeral

[clrcrl]

Yah, related issue here