Spreadsheet view for Dynamic Data Lists does not work with repeatable fields

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 6.2.X EE, 7.0.X EE, Master
• Fix Version/s: 6.2.X EE, 7.0.0 DXP FP22, 7.0.0 DXP SP4, 7.0.X EE, 7.0.4 CE GA5, 7.1.X, Master
• Component/s: Dynamic Data Lists > Admin
• Labels:
  • fw_code_review
  • liferay-digital-enterprise-70-sp4
  • liferay-fixpack-de-22-7010
  • liferay-fixpack-portal-162-6210
• Branch Version/s:
  7.0.x, 6.2.x
• Backported to Branch:
  Committed
• Fix Priority: 3
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/49440

When viewing a Dynamic Data List in "spreadsheet view," fields that are repeatable will either not display correctly, or cause the page to fail to load with a stack trace in the console.

Steps to reproduce:

1. From Content administration -> Dynamic Data Lists, click "Manage Data Definitions"
2. Add two new data definitions
   • Give the first data definition a repeatable text field
   • Give the second data definition a repeatable Documents and Media field
3. Navigate back to Dynamic Data Lists, and add two new lists (one based on each of the new DDMStructures)
4. Add a basic document to Documents and Media
5. Add a record to each of the new Dynamic Data Lists, and fill out the repeatable fields (input text for one, select the new document for the other)
   • (optional) Add and fill out extra repetitions of the repeatable field when creating the record to make the bug more obvious
6. Navigate back to Dynamic Data Lists, and for each one, click the actions menu and click "Spreadsheet View"
   Expected results: Both lists display correctly, where the values for the repeatable fields are shown in a comma-separated list.
   Actual result: The list with a repeatable text field loads, but the values are incorrect (they are references to a String array, like "[Ljava.lang.String;@5169d8e"). The list with a repeatable Documents and Media field fails to load, and an error and stack trace (as shown below) are shown in the console.

Reproduced in master: 032d2d360479e459f65f351490046c315bd94f5a
Reproduced in ee-7.0.x: de1b3f18ecf6fc5f2c52e55e54bafa9f51693857
Reproduced in ee-6.2.x: 935675a0637bdf7554ccf45ad6ae4f082c3b9439