[CT-1591] Don't parse empty Python files

[aranke]

Resolves #6367

Description

Only parse Python AST if body is not empty

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development, and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[aranke]

I've confirmed the following, I think PR should be good to merge?

1. This PR resolves the issue (see ¹ and ²).
2. The empty Python model is ignored during dbt run² and dbt ls³, just like an empty SQL model.
3. The empty Python model⁴ is shown in the dbt DAG, just like an empty SQL model.

P.S. I misclicked on closing this PR, hence the noise below.

Footnotes

1. Old dbt run

   ❯ dbt run
   06:14:26  Running with dbt=1.3.1
   06:14:27  Encountered an error:
   Parsing Error in model empty (models/challenges/py/empty.py)
     dbt only allow one model defined per python file
   

   ↩

2. New dbt run:

   ❯ dbt run
   06:14:49  Running with dbt=1.4.0-b1
   06:14:49  Unable to do partial parsing because a project config has changed
   06:14:50  Found 6 models, 4 tests, 0 snapshots, 0 analyses, 415 macros, 0 operations, 0 seed files, 6 sources, 0 exposures, 0 metrics
   06:14:50  Using default selector default
   06:14:50
   06:14:51  Concurrency: 8 threads (target='snowflake')
   06:14:51
   06:14:51  1 of 5 START sql table model dbt_karanke.stg_customers ......................... [RUN]
   06:14:51  2 of 5 START sql table model dbt_karanke.stg_orders ............................ [RUN]
   06:14:55  1 of 5 OK created sql table model dbt_karanke.stg_customers .................... [SUCCESS 1 in 3.02s]
   06:14:55  3 of 5 START python table model dbt_karanke.int_customers ...................... [RUN]
   06:15:07  2 of 5 OK created sql table model dbt_karanke.stg_orders ....................... [SUCCESS 1 in 15.75s]
   06:15:10  3 of 5 OK created python table model dbt_karanke.int_customers ................. [SUCCESS 1 in 15.42s]
   06:15:10  4 of 5 START python table model dbt_karanke.int_orders ......................... [RUN]
   06:16:08  4 of 5 OK created python table model dbt_karanke.int_orders .................... [SUCCESS 1 in 58.26s]
   06:16:08  5 of 5 START python table model dbt_karanke.unfuzz_py .......................... [RUN]
   06:16:40  5 of 5 OK created python table model dbt_karanke.unfuzz_py ..................... [SUCCESS 1 in 32.04s]
   06:16:40
   06:16:40  Finished running 5 table models in 0 hours 1 minutes and 50.46 seconds (110.46s).
   06:16:40
   06:16:40  Completed successfully
   06:16:40
   06:16:40  Done. PASS=5 WARN=0 ERROR=0 SKIP=0 TOTAL=5
   

   ↩ ↩²

3. New dbt ls:

   ❯ dbt ls
   demo_data.intermediate.int_customers
   demo_data.intermediate.int_orders
   demo_data.staging.stg_customers
   demo_data.staging.stg_orders
   demo_data.challenges.py.unfuzz_py
   demo_data.staging.not_null_stg_customers_customer_id
   demo_data.staging.not_null_stg_orders_order_id
   demo_data.staging.unique_stg_customers_customer_id
   demo_data.staging.unique_stg_orders_order_id
   

   ↩

4. New dbt DAG:
   ↩

[ChenyuLInx]

Looks great!! Thanks for testing out the behavior of run, list and doc

[hope-wat]

With this change now being live should we not be seeing this behavior anymore in dbt cloud?

I just created a new .py file and this threw the same problem. I was the original poster/opened the bug with the corresponding loom so I am not resposting here in the comment.