[CT-722] DuplicateYamlKeyException needs to be warning, not (broken) exception

[jtcohen6]

Net-new bug in v1.2. See also #5268, which I believe is caused by the same root change (#5146).

dbt-core/core/dbt/clients/yaml_helper.py

Lines 75 to 88 in eea872c

	def load_yaml_text(contents, path=None):
	try:
	return safe_load(contents)
	except (yaml.scanner.ScannerError, yaml.YAMLError) as e:
	if hasattr(e, "problem_mark"):
	error = contextualized_yaml_error(contents, e)
	else:
	error = str(e)
	raise dbt.exceptions.ValidationException(error)
	except dbt.exceptions.DuplicateYamlKeyException as e:
	# TODO: We may want to raise an exception instead of a warning in the future.
	e.msg = f"{e} {path.searched_path}/{path.relative_path}."
	dbt.exceptions.warn_or_raise(e, log_fmt=warning_tag("{}"))

If path=None, it has no searched_path / relative_path. If I change that to

Reproduction case

# dbt_project.yml
vars:
  one_var: foo
  one_var: bar

$ dbt parse
17:20:39  Encountered an error:
'NoneType' object has no attribute 'searched_path'

If I change the code linked above to:

     except dbt.exceptions.DuplicateYamlKeyException as e: 
         # TODO: We may want to raise an exception instead of a warning in the future. 
         if path:
             e.msg = f"{e} {path.searched_path}/{path.relative_path}." 
         dbt.exceptions.warn_or_raise(e, log_fmt=warning_tag("{}")) 

$ dbt parse
17:21:36  [WARNING]: Compilation Error
  Duplicate 'one_var' key found in yaml file
17:21:36  Encountered an error while reading the project:
17:21:36    ERROR: Runtime Error
  dbt_project.yml does not parse to a dictionary
17:21:36  Encountered an error:
Runtime Error
  Could not run dbt

This is still a problem. This parses successfully in v1.1. We MUST make this a warning, not an error.

We can do that by using SafeLoader instead of UniqueKeyLoader, and still returning the loaded result (if not --warn-error):

    except dbt.exceptions.DuplicateYamlKeyException as e:
        if path:
            # TODO: We may want to raise an exception instead of a warning in the future.
            e.msg = f"{e} {path.searched_path}/{path.relative_path}."
        dbt.exceptions.warn_or_raise(e, log_fmt=warning_tag("{}"))
        return yaml.load(contents, Loader=SafeLoader)