Way to validate if input is actually a YAML

[vmatt]

CHECK_YAML only return the error message, if the input contains some YAML, but it's malformed. However, it silently fails, if we just pass a single string, without any newlines, or tabulation.

Current behavior

SELECT CHECK_YAML('"not a valid YAML"'); -> null
SELECT YAML_TO_JSON('not a valid YAML'); -> "not a valid YAML".

Expected behavior

SELECT CHECK_YAML('"not a valid YAML"'); -> "ERROR: invalid YAML"
SELECT YAML_TO_JSON('not a valid YAML'); -> null (maybe "ERROR: Invalid YAML" would be better)

[hunyadi]

I am not sure I understand. A single quoted string is a valid YAML document. By definition, CHECK_YAML should return NULL only if the input is well-formed, in alignment with Snowflake's own CHECK_JSON.