Motivation

I've noticed while working on other kind of VTL template that we were not handling $input.path and $input.json return values correctly when the body would be empty, or the JSONPath would point to a non-existent value or the body would not be JSON.

There were several reasons:

• the default extract_jsonpath helper method from LocalStack builds the result in a list, and return an empty list if there are no result. Because of this, we can't differentiate if we're actually fetching an empty list via the JSONPath, or we actually did not find a match. We now properly return None and verify behavior
• we would return an empty dict by default if there were no body, but this isn't the right behavior from AWS. We'd need new tests with request templates again to validate, I've checked it with the AWS console and multiple scenarios and external tests that this is the right behavior
• we would not support string value as body when using input.path or input.json. In AWS, it does not fail but instead fallback to returning null

Changes

• use special extract_jsonpath for VTL rendering to stop returning empty list when no match
• stop returning an empty dict when there is no body when calling input.path or input.body
• add tests case
• update unit tests with finding from AWS console

Testing

External run number: 15740672033 (good for this change)