Feature/vars per environment

[andeerlb]

https://docs.getdbt.com/docs/build/project-variables

Problem

dbt did not support environment-specific or test-specific variable files. All variables had to be managed in a single vars.yml or dbt_project.yml, making it difficult to isolate configuration for different environments (dev, staging, prod) or for test runs.

Solution

• Added support for loading and merging vars.yml and vars_<target>.yml at the project root. When running dbt with a specific target (via --target), variables from vars_<target>.yml override those in vars.yml for that environment.
• Added support for tests/vars.yml and tests/vars_<target>.yml. When running dbt test, these files are loaded and merged (with target-specific vars taking precedence), and their variables override project-level vars for tests only.
• The loader for test vars is robust: if the test vars files are missing or malformed, they are ignored and dbt continues without error. Project vars remain available for all commands, including tests.
• Test-specific vars are only loaded and merged during dbt test. Other commands (dbt run, dbt build, etc.) are unaffected and ignore the test vars files.

Why is this useful?

• Environment-specific configuration:
  Allows teams to manage variables for different environments (dev, staging, prod, etc.) in separate files, reducing risk of accidental changes and making configuration clearer.
• Test isolation:
  Enables tests to use their own variables without affecting production runs or requiring changes to project-level vars.

How to use

• Place environment-specific vars in vars.yml and vars_<target>.yml at the project root.
• Place test-specific vars in tests/vars.yml and tests/vars_<target>.yml.
• When running dbt test, test vars will override project vars for tests only.
• When running other commands, only project vars are used.
• Here is an example how to use https://github.com/andeerlb/dbt_config_per_env_example/tree/master

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[github-actions]

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