[RensTillmann]

Summary

On 6.4.0xx a form with an empty field that has a validation rule (for example numeric or email) inside a column set to invisible is rejected by the server with "Please fill in all required fields.", although the browser accepted it: validate_form skips fields under an invisible column (has_hidden_parent() defaults includeInvisibleColumns to true), but the payload still submits them and SUPER_Ajax::collect_required_fields() enrolled them as required.

Fix: collect_required_fields() skips the subtree of a column whose invisible is true, matching the browser. Hidden fields and the payload JS are unchanged.

Replaces the 6.4 part of closed #219 (which targeted the archived stable branch). LTS is not affected: its has_hidden_parent() has no invisible-column check, so client and server already agree there.

Base branch

release/6.4.x: bug fix for the beta channel (frozen: security and bug fixes only). Not needed on lts/6.3.x (see above).

Tests

PHPUnit, new Test_Super_Forms_Required_Fields_Invisible_Column (g16-phpunit:wp7.1.1-php8.2 + MariaDB 11.4):
  without the fix: 2 failures (field "amount" in an invisible column is enrolled)
  with the fix:    OK (5 tests, 10 assertions)
Full PHPUnit suite with the fix: OK, 617 tests, 10295 assertions, 1 skipped
node --test tests/test-validation-client.cjs: 42 pass, 0 fail
run-validation-compatibility.py --group layout (real submit_form, SQLite dev bootstrap):
  without the fix: 26/28 (layout-invisible-column-validated-empty and its flat twin fail)
  with the fix:    28/28

Changelog: src/docs/changelog.md gets an "Unreleased - Version 6.4.010-beta" section with one Fix line.

Merge

Draft: for QA and the next 6.4.0xx release session; not merged by the author.

[RensTillmann]

The fix is already released in 6.4.010 (release PR #299, merged 21 Oct 2026): src/includes/class-ajax.php line 8694 skips invisible columns in collect_required_fields(). This PR's two repo tests were not part of that release and stay on this branch. The browser suite covers this on 6.4.010 (invisible-column.spec.ts, 2 tests passed).