Allow to patch (navigate patching the content) to another site (#621)

lib/beacon/private.ex

@@ -0,0 +1,39 @@
+defmodule Beacon.Private do
+  @moduledoc false
+
+  # Concentrate calls to private APIs so it's easier to track breaking changes and document them,
+  # in case we need to make changes or understand why we had to call such APIs.
+
+  # Should be avoided as much as possible.
+
+  @doc """
+  On page navigation, the request might actually hit a different site than the one defined by the current session.
+
+  That's the case for a live patch to a full URL, for eg:
+
+  User is in https://sitea.com/page1 and clicks on a link to https://siteb.com/page2 through a `<.link patch={...}>` component,
+  and since LV allows such navigation, we must do it as well but we need fetch the session defined for the requested URL and update the state accordingly,
+  otherwise the page will either not be found or worse could render the wrong content.
+
+  Relative paths are not supported because there's no safe way to know if a `/relative` path belongs to site A or B, that's a LV contraint.
+
+  We use the private function `Phoenix.LiveView.Route.live_link_info/3` in order to keep the same behavior as LV.
+  """
+  def site_from_session(endpoint, router, url, view) do
+    case Phoenix.LiveView.Route.live_link_info(endpoint, router, url) do
+      {_,
+       %{
+         view: ^view,
+         live_session: %{
+           extra: %{
+             session: %{"beacon_site" => site}
+           }
+         }
+       }} ->
+        site
+
+      _ ->
+        nil
+    end
+  end
+end

lib/beacon/pub_sub.ex

@@ -56,6 +56,10 @@ defmodule Beacon.PubSub do
     Phoenix.PubSub.subscribe(@pubsub, topic_page(site, path))
   end
 
+  def unsubscribe_to_page(site, path) do
+    Phoenix.PubSub.unsubscribe(@pubsub, topic_page(site, path))
+  end
+
   def page_loaded(%Content.Page{} = page) do
     page.site
     |> topic_page(page.path)

lib/beacon/web/live/page_live.ex

@@ -96,25 +96,39 @@ defmodule Beacon.Web.PageLive do
     end
   end
 
-  def handle_params(params, _url, socket) do
-    %{beacon: %{site: site}} = socket.assigns
-    %{"path" => path_info} = params
-    page = RouterServer.lookup_page!(site, path_info)
-    live_data = Beacon.Web.DataSource.live_data(site, path_info, Map.drop(params, ["path"]))
-    beacon_assigns = BeaconAssigns.new(site, page, live_data, path_info, params)
-
-    socket =
-      socket
-      |> Component.assign(live_data)
-      # TODO: remove deprecated @beacon_live_data
-      |> Component.assign(:beacon_live_data, live_data)
-      # TODO: remove deprecated @beacon_path_params
-      |> Component.assign(:beacon_path_params, beacon_assigns.path_params)
-      # TODO: remove deprecated @beacon_query_params
-      |> Component.assign(:beacon_query_params, beacon_assigns.query_params)
-      |> Component.assign(:beacon, beacon_assigns)
-
-    {:noreply, push_event(socket, "beacon:page-updated", %{meta_tags: Beacon.Web.DataSource.meta_tags(socket.assigns)})}
+  def handle_params(params, url, socket) do
+    case Beacon.Private.site_from_session(socket.endpoint, socket.router, url, __MODULE__) do
+      nil ->
+        raise Beacon.Web.NotFoundError, """
+        no page was found for url #{url}
+
+        Make sure a page was created for that url.
+        """
+
+      site ->
+        %{"path" => path_info} = params
+        page = RouterServer.lookup_page!(site, path_info)
+        live_data = Beacon.Web.DataSource.live_data(site, path_info, Map.drop(params, ["path"]))
+        beacon_assigns = BeaconAssigns.new(site, page, live_data, path_info, params)
+
+        if socket.assigns.beacon.site != site do
+          Beacon.PubSub.unsubscribe_to_page(socket.assigns.beacon.site, path_info)
+          Beacon.PubSub.subscribe_to_page(site, path_info)
+        end
+
+        socket =
+          socket
+          |> Component.assign(live_data)
+          # TODO: remove deprecated @beacon_live_data
+          |> Component.assign(:beacon_live_data, live_data)
+          # TODO: remove deprecated @beacon_path_params
+          |> Component.assign(:beacon_path_params, beacon_assigns.path_params)
+          # TODO: remove deprecated @beacon_query_params
+          |> Component.assign(:beacon_query_params, beacon_assigns.query_params)
+          |> Component.assign(:beacon, beacon_assigns)
+
+        {:noreply, push_event(socket, "beacon:page-updated", %{meta_tags: Beacon.Web.DataSource.meta_tags(socket.assigns)})}
+    end
   end
 
   @doc false

test/beacon_web/live/page_live_test.exs

@@ -68,6 +68,7 @@ defmodule Beacon.Web.Live.PageLiveTest do
           @beacon.query_params=<%= @beacon.query_params["query"] %>
 
           <.page_link path="/about">go_to_about_page</.page_link>
+          <.link patch={"#{Beacon.BeaconTest.Endpoint.url()}/other"}>go_to_other_site</.link>
 
           <.form :let={f} for={%{}} as={:greeting} phx-submit="hello">
             Name: <%= text_input f, :name %>
@@ -131,6 +132,14 @@ defmodule Beacon.Web.Live.PageLiveTest do
         meta_tags: nil
       )
 
+    beacon_published_page_fixture(
+      site: :not_booted,
+      path: "/",
+      template: """
+      <h1><%= @beacon.site %></h1>
+      """
+    )
+
     [layout: layout]
   end
 
@@ -157,6 +166,16 @@ defmodule Beacon.Web.Live.PageLiveTest do
            |> render_click() =~ "about_page"
   end
 
+  test "patch to another site resets site data", %{conn: conn} do
+    {:ok, view, _html} = live(conn, "/home/hello")
+
+    view
+    |> element("a", "go_to_other_site")
+    |> render_click()
+
+    assert has_element?(view, "h1", "not_booted")
+  end
+
   describe "meta tags" do
     test "merge layout, page, and site", %{conn: conn} do
       {:ok, _view, html} = live(conn, "/home/hello")

test/support/router.ex

@@ -17,6 +17,7 @@ defmodule Beacon.BeaconTest.Router do
 
   scope "/" do
     pipe_through :browser
+    beacon_site "/other", site: :not_booted
     beacon_site "/", site: :my_site
   end
 end