Why

It seems that behavior has changed when UITableView#heightForHeaderInSection behavior return 0 and return tableView.sectionHeaderHeight(-1) when it becomes iOS 11. Also delegate for footer has same problem.

Problem

When Using grouped style UITableView

• Until then(iOS 10.*)
  • When return 0 in heightForHeaderInSection, setting UIKIt/UITableView configured implicity default height(about 20px).
  • When return -1, setting UIKIt/UITableView configured implicity default height(about 20px).
• iOS 11
  • When return 0 in heightForHeaderInSection, setting truth zero height. (This is different from then)
  • When return -1, setting UIKIt/UITableView configured implicity default height(about 20px).

When Using plain style UITableView

• Until then(iOS 10.*)
  • When return 0 in heightForHeaderInSection, setting truth zero height.
  • When return -1, setting ` setting zero height.
• iOS 11
  • When return 0 in heightForHeaderInSection, setting truth zero height.
  • When return -1, setting UIKIt/UITableView configured implicity default height(about 20px). (This is different from then)

I faced when using grouped UITableView and not instanciate SectionHeaderFooterType.height(or heightFor(_:section:)).
So, using Shoyu return 0 height via UITableView#heightForHeaderInSection delegate method in this case.

But I confirmed iOS 10.3 simulator and iOS 11 simulator get difference height for header at this time.

How to resolve

I guess necessary switch for UITableView.style about returning height for delegate method.
Grouped UITableView returning always tableView.sectionHeaderHeight when not configure SectionHeaderFooterType.height(or heightFor(_:section:)). Plain UITableViewreturning always0when not configure SectionHeaderFooterType.height(or heightFor(_:section:)).

I guess it is necessary switch of UITableView.style about returning height for delegate method
Grouped style UITableView return tableView.sectionHeaderHeight when not configure SectionHeaderFooterType.height(or heightFor(_:section:)).
Plain style UITableView return always 0 when not configure SectionHeaderFooterType.height(or heightFor(_:section:)).

Plaase check this issue problem.
Thank you.