Collapse line-height in ToggleSwitch status icon slot so the spinner sits on centre

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 14f13505-d338-494c-a7df-96616e27c88f

Author: gabrielhl

app/components/primer/alpha/toggle_switch.pcss

@@ -189,6 +189,8 @@
   justify-content: center;
   width: var(--base-size-16);
   height: var(--base-size-16);
+  /* stylelint-disable-next-line primer/typography */
+  line-height: 0;
   /* stylelint-disable-next-line primer/spacing */
   margin-top: 0.063rem;
 }

test/system/alpha/toggle_switch_test.rb

@@ -136,6 +136,17 @@ def test_switch_does_not_move_when_error_icon_is_shown
       assert_in_delta before_top, track_top, 0.5
     end
 
+    def test_loading_spinner_is_centered_in_the_status_icon_slot
+      visit_preview(:small)
+
+      unhide(find("[data-target='toggle-switch.loadingSpinner']", visible: :hidden))
+      assert_selector("[data-target='toggle-switch.loadingSpinner']")
+
+      assert_in_delta vertical_center(find("[data-target='toggle-switch.loadingSpinner'] svg")),
+                      vertical_center(find(".ToggleSwitch-statusIcon")),
+                      0.5
+    end
+
     private
 
     # The status icons are hidden with the `hidden` attribute. `hidden` is an HTMLElement IDL
@@ -149,6 +160,13 @@ def track_top
       evaluate_script("arguments[0].getBoundingClientRect().top;", find(".ToggleSwitch-track"))
     end
 
+    def vertical_center(element)
+      evaluate_script(
+        "(function (r) { return r.top + r.height / 2; })(arguments[0].getBoundingClientRect());",
+        element
+      )
+    end
+
     def wait_for_spinner
       refute_selector("[data-target='toggle-switch.loadingSpinner']")
     end