Stabilize realtime discovery pagination

lib/who_need_help_web/live/activity_live/index.ex

@@ -68,21 +68,6 @@ defmodule WhoNeedHelpWeb.ActivityLive.Index do
     user_id = socket.assigns.current_scope.user.id
     already_mine? = Enum.any?(socket.assigns.my_activities, &(&1.id == activity.id))
 
-    {activities, activities_cursor} =
-      update_entry(
-        socket.assigns.activities,
-        activity,
-        not is_nil(socket.assigns.viewport) and
-          Activities.visible_open_activity?(
-            socket.assigns.current_scope,
-            activity,
-            socket.assigns.filters,
-            socket.assigns.viewport
-          ),
-        :asc,
-        socket.assigns.activities_cursor
-      )
-
     {my_activities, my_activities_cursor} =
       update_entry(
         socket.assigns.my_activities,
@@ -94,12 +79,14 @@ defmodule WhoNeedHelpWeb.ActivityLive.Index do
 
     socket =
       socket
-      |> assign(:activities, activities)
-      |> assign(:activities_cursor, activities_cursor)
       |> assign(:my_activities, my_activities)
       |> assign(:my_activities_cursor, my_activities_cursor)
 
-    if socket.assigns.refresh_timer || socket.assigns.view_mode == "list" do
+    # A single authoritative page reload keeps the list, cursor, result count,
+    # and map clusters on the same database snapshot. Applying the PubSub item
+    # locally and then accepting an in-flight async page allowed an older page
+    # to overwrite a newer bounded window during bursts.
+    if socket.assigns.refresh_timer do
       {:noreply, socket}
     else
       timer = Process.send_after(self(), :refresh_discovery, 100)

test/who_need_help_web/live/mutual_aid_live_test.exs

@@ -665,7 +665,11 @@ defmodule WhoNeedHelpWeb.MutualAidLiveTest do
     first = List.first(requests)
     overflow = List.last(requests)
 
-    assert_eventually(fn -> has_element?(view, "#open-request-#{first.id}") end)
+    assert_eventually(fn ->
+      has_element?(view, "#open-request-#{first.id}") and
+        has_element?(view, "button", "Load more in this area")
+    end)
+
     refute has_element?(view, "#open-request-#{overflow.id}")
 
     view |> element("button", "Load more in this area") |> render_click()
@@ -704,7 +708,7 @@ defmodule WhoNeedHelpWeb.MutualAidLiveTest do
         "safety_confirmed" => true
       })
 
-    assert render(view) =~ "Realtime coffee meetup"
+    assert_eventually(fn -> render(view) =~ "Realtime coffee meetup" end)
   end
 
   test "activity realtime updates keep a bounded window without skipping pagination" do
@@ -738,11 +742,14 @@ defmodule WhoNeedHelpWeb.MutualAidLiveTest do
         activity
       end
 
-    render(view)
     first = List.first(activities)
     overflow = List.last(activities)
 
-    assert has_element?(view, "#open-activity-#{first.id}")
+    assert_eventually(fn ->
+      has_element?(view, "#open-activity-#{first.id}") and
+        has_element?(view, "button", "Load more")
+    end)
+
     refute has_element?(view, "#open-activity-#{overflow.id}")
 
     view |> element("button", "Load more") |> render_click()