ARROW-11838: fix offset buffer in golden file.

[jmgpeeters]

Chasing the Java integration errors in apache/arrow#9629 (although C++ passes), it appears I misunderstood the correct layout for the offset buffer (for ["foo", "bar", "baz"] needs to be [0, 3, 6, 9] and not [0, 3, 6]).

I have fixed this and verified locally that it works with both C++ and Java. Sorry about that.

@pitrou has context on this, so probably a good one to review.

[pitrou]

Hmm, C++ shouldn't have accepted the non-conformant buffer. Can you try to find where the missing checks need to be added?

[jmgpeeters]

Yep, will do.

[jmgpeeters]

@pitrou I've implemented some additional checks in the Arrow sister PR. The C++ integration check (https://github.com/apache/arrow/pull/9629/checks?check_run_id=2142504660) now fails with:

RuntimeError: Command failed: /build/cpp/debug/arrow-json-integration-test --integration --arrow=/arrow/testing/data/arrow-ipc-stream/integration/4.0.0-shareddict/generated_shared_dict.arrow_file --json=/tmp/tmprjve0h7q/4.0.0-shareddict_shared_dict.gold.json --mode=VALIDATE
With output:
--------------
Error message: Invalid: JSON OFFSET array size differs from advertised array length + 1

(i.e. because [0, 3, 6] is one too short).

and it has similarly useful errors (verified locally) if

• OFFSETs is missing altogether
• one would do e.g. [0, 3, 6, 10] instead of the correct [0, 3, 6, 9]

[pitrou]

+1, thank you @jmgpeeters