get_source_schemas function checks yaml files that are located outside of dbt project's directory

[tahseenadit]

Describe the bug
I have a subdirectory inside my root directory. The subdirectory contains all dbt files like models, macros, tests, seeds etc. I have .yaml files inside the root directory and the subdirectory. I have defined a .pre-commit-config.yaml file inside the subdirectory. One of the .yaml files in my root directory is empty (I have kept it intentionally for testing purpose).

When I invoke pre-commit programmatically from a file, I get an error because of that empty .yaml file.

Check for source column descriptions.....................................Failed
- hook id: check-source-columns-have-desc
- exit code: 1

Traceback (most recent call last):
  File "/Users/mdana/.cache/pre-commit/repoyj6tusf_/py_env-python3.9/bin/check-source-columns-have-desc", line 8, in <module>
    sys.exit(main())
  File "/Users/mdana/.cache/pre-commit/repoyj6tusf_/py_env-python3.9/lib/python3.9/site-packages/dbt_checkpoint/check_source_columns_have_desc.py", line 54, in main
    hook_properties = check_column_desc(
  File "/Users/mdana/.cache/pre-commit/repoyj6tusf_/py_env-python3.9/lib/python3.9/site-packages/dbt_checkpoint/check_source_columns_have_desc.py", line 25, in check_column_desc
    for schema in schemas:
  File "/Users/mdana/.cache/pre-commit/repoyj6tusf_/py_env-python3.9/lib/python3.9/site-packages/dbt_checkpoint/utils.py", line 343, in get_source_schemas
    for source in schema.get("sources", []):
AttributeError: 'NoneType' object has no attribute 'get'

To Reproduce
Steps to reproduce the behavior:

1. Create an empty .yml file in any directory in your project.
2. Run pre-commit hook check_source_columns_have_desc

Example pre-commit-config.yaml file:

repos:
- repo: https://github.com/offbi/pre-commit-dbt
  rev: v2.0.1
  hooks:
  - id: check-source-columns-have-desc
    args: ["--manifest", "dbt_subdir/target/manifest.json"]

Expected behavior
By default the hook should only check .yaml files that are inside the dbt project's directory i.e dbt_subdir and raise error if any of the .yaml files stored inside dbt project's directory is empty.

Suggestion:

def get_source_schemas(
    yml_files: Sequence[Path], include_disabled: bool = False
) -> Generator[SourceSchema, None, None]:
    # There should be a logic here to filter yml_files
    for yml_file in yml_files:
        schema = safe_load(yml_file.open())
        for source in schema.get("sources", []):
            if not include_disabled and not source.get("config", {}).get(
                "enabled", True
            ):
                continue
            source_name = source.get("name")
            tables = source.pop("tables", [])
            for table in tables:
                table_name = table.get("name")
                yield SourceSchema(
                    source_name=source_name,
                    table_name=table_name,
                    filename=yml_file.stem,
                    source_schema=source,
                    table_schema=table,
                )

Version:
v2.0.1

Additional context
Debug output:
hook.id: 'check-source-columns-have-desc'
hook.files: ''
hook.exclude: '^$'
hook.types: ['file']
hook.types_or: ['yaml']
hook.exclude_types: []

filenames
('.github/workflows/pr...checks.yml', '.empty-test-pre-commit-config.yaml', 'Taskfile.yml', 'dbt_bq/.pre-commit-config.yaml', 'dbt_bq/.user.yml', 'dbt_bq/dbt_project.yml', 'dbt_bq/dependencies.yml', 'dbt_bq/macros/schema.yml', 'dbt_bq/models/exampl...schema.yml', 'dbt_bq/profiles.yml', 'dbt_bq/seeds/example...erties.yml')
special variables
function variables
00: '.github/workflows/pre_commit_checks.yml'
01: '.empty-test-pre-commit-config.yaml'
02: 'Taskfile.yml'
03: 'dbt_bq/.pre-commit-config.yaml'
04: 'dbt_bq/.user.yml'
05: 'dbt_bq/dbt_project.yml'
06: 'dbt_bq/dependencies.yml'
07: 'dbt_bq/macros/schema.yml'
08: 'dbt_bq/models/example/schema.yml'
09: 'dbt_bq/profiles.yml'
10: 'dbt_bq/seeds/example/properties.yml'
len(): 11