[ARROW-10208] [C++] String split kernels do not propagate nulls correctly on sliced input

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/26212
• Assignee: Antoine Pitrou
• Reporter: Maarten Breddels
• Created: 07/Oct/20 09:23
• Updated: 11/Jan/23 08:11
• Resolved: 22/Oct/20 16:19

Description

I am not sure if this is a specific test issue or valid behavior, but when writing a test in https://github.com/apache/arrow/pull/8271 

The following test fails:

this->CheckUnary("split_pattern", R"(["foo bar", "foo", null])", list(this->type()),  //                  R"([["foo", "bar"], ["foo"], null])", &options);

with the following output

Failed:
Got: 
  [
    [
      [
        "foo",
        "bar"
      ]
    ],
    [
      [
        "foo"
      ],
      null
    ]
  ]
Expected: 
  [
    [
      [
        "foo",
        "bar"
      ]
    ],
    [
      [
        "foo"
      ],
      null
    ]
  ]

while the outputs are the same, the arrays are seen as unequal.

Issue Links

• links to: GitHub Pull Request #8496