Let data-show-time turn time off as well as on

spec/per_element_options_spec.rb

@@ -27,4 +27,16 @@ def value_of(wrapper_id)
 
     expect(value_of('post_created_at_input')).to eq(today.strftime('%Y-%m-%d 00:00:00'))
   end
+
+  # show_time passed to the call is the documented way to turn time on for a
+  # group of inputs. data-show-time="false" is then the only way for one of
+  # them to opt out, and the attribute was write-only: the guard assigned
+  # true and never false.
+  it 'lets data-show-time="false" opt back out of a call that asked for time' do
+    page.execute_script("$('.manual_preset_pair').date_range_ext_preset({ show_time: true });")
+
+    pick_today_in('post_title_input')
+
+    expect(value_of('post_title_input')).to eq((today + 1).strftime('%Y-%m-%d'))
+  end
 end

spec/support/admin.rb

@@ -37,6 +37,10 @@ def add_post_resource_with_two_pairs
         f.input :created_at, as: :string,
                 wrapper_html: { class: 'datetime_preset_pair', data: { show_time: 'true' } }
         f.input :updated_at, as: :string
+        # Not .datetime_preset_pair, so the auto-init leaves it alone and the
+        # spec can drive it with explicit options.
+        f.input :title, as: :string,
+                wrapper_html: { class: 'manual_preset_pair', data: { show_time: 'false' } }
       end
       f.actions
     end

vendor/assets/javascripts/active_admin_date_range_preset.js

@@ -60,8 +60,11 @@ $(function () {
       // click time rather than here, so the leak was not even order-dependent.
       let el_opts = $.extend({}, opts);
 
-      if (typeof $this.data('show-time') != 'undefined' && $this.data('show-time').toString() == 'true') {
-        el_opts.show_time = true;
+      // The attribute is authoritative in both directions when present. Only
+      // ever assigning true made it impossible for one element to opt out of
+      // a show_time the call or the defaults had turned on.
+      if (typeof $this.data('show-time') != 'undefined') {
+        el_opts.show_time = $this.data('show-time').toString() == 'true';
       }
 
       // detect inputs