Prior to this commit, the exists() method in JsonPathExpectationsHelper
correctly asserted that the evaluated JsonPath expression resulted in a
value (i.e., that a non-null value exists); however, if the value was
an empty array, the exists() method always threw an AssertionError.
The existing behavior makes sense if the JsonPath expression is
'indefinite' -- for example, if the expression uses a filter to select
results based on a predicate for which there is no match in the JSON
document, but the existing behavior is illogical and therefore invalid
if the JsonPath expression is 'definite' (i.e., directly references an
array in the JSON document that exists but happens to be empty). For
example, prior to this commit, the following threw an AssertionError.
new JsonPathExpectationsHelper("$.arr").exists("{ 'arr': [] }");
Similar arguments can be made for the doesNotExist() method.
After thorough analysis of the status quo, it has become apparent that
the existing specialized treatment of arrays is a result of the fact
that the JsonPath library always returns an empty list if the path is
an 'indefinite' path that does not evaluate to a specific result.
Consult the discussion on "What is Returned When?" in the JsonPath
documentation for details:
https://github.com/jayway/JsonPath#what-is-returned-when
This commit addresses these issues by ensuring that empty arrays are
considered existent if the JsonPath expression is definite but
nonexistent if the expression is indefinite.
Issue: SPR-13351
07bb0378b9