JSON_QUERY returns a container out of a document that is broken, when the break lies past the matched path

JSON_QUERY is documented to return NULL when it is not given a valid
JSON document. Like its scalar sibling it stops at the matched path, so
a break past the match is never met and the container is returned.

SELECT JSON_QUERY('{"a":{"k":1} "b":2}', '$.a') AS v;

v

{"k":1}

No warning. The outer document has no comma between its members and is
not a JSON document.

How to repeat

-- the break is past the match: answered, silently

SELECT JSON_QUERY('{"a":{"k":1} "b":2}', '$.a') AS v;   -- {"k":1}

SELECT JSON_QUERY('{"a":{"k":1},"b":}', '$.a')  AS v;   -- {"k":1}

SELECT JSON_QUERY('{"a":{"k":1}}}', '$.a')      AS v;   -- {"k":1}

-- the break moved in front of the match: NULL

SELECT JSON_QUERY('{"b":,"a":{"k":1}}', '$.a')  AS v;   -- NULL

Root cause

The same shape as the scalar form: the function returns at the match and
the rest of the document is not read.

Contract, `scripts/fill_help_tables.sql:457` (topic 383): *"Returns NULL
if not given a valid JSON document, or if there is no match."*

Affected versions

JSON_QUERY was added in 10.2.3.

Verified on 10.11 only (10.11.19-MariaDB-debug, commit 1dab253482d).
Other branches were not tested.

Note

Found while auditing the JSON functions against their documented
contracts. Partial. func_json_invalid.test:71 covers only
'{"a":1,' and records NULL there for the unrelated reason that the
path names a scalar. Nothing pins a broken document from which
JSON_QUERY does hand back a container.