[CT-998] [Bug] Provide a more helpful error when a project-level config is Undefined and cannot be deepcopied

[jesperdejby]

Is this a new bug in dbt-core?

• [X] I believe this is a new bug in dbt-core
• [X] I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

DBT version 1.0.0 Plugins:

• bigquery: 1.0.0

I tried executing dbt run --select my_model with the following syntax in my dbt_project.yml file:

dwh:
  +database: db_name
  dataset:
    +schema: schema_name
    +grant_access_to:
      - project: "{{ 'dwh-prod' if target.name == 'prod' }}"
        dataset: mydataset

The IF statement - project: "{{ 'dwh-prod' if target.name == 'prod' }}" is incomplete and will return the error message:

cannot pickle 'Undefined' object

Expected Behavior

If you want to grant access to this project you could just write: - project: prod. I expect the error message to be more descriptive than:

cannot pickle 'Undefined' object

If you get a hint on that the if-statement can't be parsed or something along these lines you could identify where the problem lies. I managed to reverse engineer this by finding https://github.com/dbt-labs/dbt-core/issues/2110 and concluding this was not caused by my models/refs and I started looking into the dbt_project.yml file.

Steps To Reproduce

1. Be connected to a BigQuery db
2. Replace the following targets in your project.yml files with ones relevant to your case: dwh: +database: db_name dataset: +schema: schema_name +grant_access_to: - project: "{{ 'dwh-prod' if target.name == 'prod' }}" dataset: mydataset
3. Create a model that uses this database/schema combination
4. Execute dbt run --select my_model and it should fail because of the incorrect IF-statement

Relevant log output

cannot pickle 'Undefined' object

### Environment

```markdown
- OS: macOS Monterey 12.4
- Python: 3.9.9
- dbt: 1.0.0

Which database adapter are you using with dbt?

bigquery

Additional Context

No response

[jtcohen6]

@jesperdejby Thanks for opening, and for the clear restatement! I was able to reproduce this quite easily.

Indeed, the issue here is that, when target.name is not prod, the Jinja expression resolves to None/Undefined, which Python cannot deepcopy. (dbt needs to deepcopy project-level configs, during config resolution at parse time.)

A temporary fix is to provide an else conditional value:

        - project: "{{ 'dwh-prod' if target.name == 'prod' else 'something_else' }}"

I agree that the error message here is not very helpful in identifying the root cause. I'm going to reframe this issue as: dbt should provide a more helpful error when a project-level config is Undefined and cannot be deepcopied.

[jesperdejby]

@jtcohen6 Thank you for the quick response and help 🙏 .

[emmyoop]

We're going to need to take a closer look to see if there is a reasonable place/way to determine when Undefined is being returned from jinja before this can be estimated.

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[github-actions[bot]]

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