Raise if the pubsub server name is not configured at compile time (ph…

…oenixframework#3068)

If the pubsub server is configured at runtime (e.g. in the init callback) then
everything will appear to work as normal, but the pubsub server will have the
name of `Elixir.Supervisor` due to having nil as a name.

This closes phoenixframework#2992

lib/phoenix/endpoint.ex

@@ -510,7 +510,8 @@ defmodule Phoenix.Endpoint do
       server
     else
       raise ArgumentError, """
-      no :pubsub server configured, please setup :pubsub in your config.
+      no :pubsub server was configured at compile time, please setup :pubsub
+      in your config.
 
       By default this looks like:
 

lib/phoenix/endpoint/supervisor.ex

@@ -54,7 +54,7 @@ defmodule Phoenix.Endpoint.Supervisor do
 
     if adapter = pub_conf[:adapter] do
       pub_conf = [fastlane: Phoenix.Channel.Server] ++ pub_conf
-      [supervisor(adapter, [mod.__pubsub_server__(), pub_conf])]
+      [supervisor(adapter, [Phoenix.Endpoint.__pubsub_server__!(mod), pub_conf])]
     else
       []
     end

test/phoenix/endpoint/endpoint_test.exs

@@ -12,6 +12,8 @@ defmodule Phoenix.Endpoint.EndpointTest do
            pubsub: [adapter: Phoenix.PubSub.PG2, name: :endpoint_pub]]
   Application.put_env(:phoenix, __MODULE__.Endpoint, @config)
 
+  Application.put_env(:phoenix, __MODULE__.NoPubSubEndpoint, Keyword.delete(@config, :pubsub))
+
   defmodule Endpoint do
     use Phoenix.Endpoint, otp_app: :phoenix
 
@@ -21,6 +23,15 @@ defmodule Phoenix.Endpoint.EndpointTest do
     assert code_reloading? == false
   end
 
+  defmodule NoPubSubEndpoint do
+    use Phoenix.Endpoint, otp_app: :phoenix
+
+    def init(_, config) do
+      pubsub = [adapter: Phoenix.PubSub.PG2, name: :named_at_runtime_endpoint_pub]
+      {:ok, Keyword.put(config, :pubsub, pubsub)}
+    end
+  end
+
   setup_all do
     Endpoint.start_link()
     on_exit fn -> Application.delete_env(:phoenix, :serve_endpoints) end
@@ -35,6 +46,12 @@ defmodule Phoenix.Endpoint.EndpointTest do
     }
   end
 
+  test "errors if pubsub is not set at runtime and not compile time" do
+    Process.flag(:trap_exit, true)
+    {:error, {%ArgumentError{message: message}, _}} = NoPubSubEndpoint.start_link()
+    assert message =~ "no :pubsub server was configured at compile time"
+  end
+
   test "has reloadable configuration" do
     assert Endpoint.config(:url) == [host: {:system, "ENDPOINT_TEST_HOST"}, path: "/api"]
     assert Endpoint.config(:static_url) == [host: "static.example.com"]