init channel errors can happen

.vscode/tasks.json

@@ -57,17 +57,17 @@
         "problemMatcher": "$mixTestFailure"
       },
       {
-        "label": "run testbed test at cursor",
+        "label": "mix test focused",
         "type": "shell",
         "command": "mix",
         "args": [
           "test",
-          "../${relativeFile}:${lineNumber}",
+          "${relativeFile}:${lineNumber}",
           "--color",
           "--trace"
         ],
         "options": {
-          "cwd": "${workspaceRoot}/testbed",
+          "cwd": "${workspaceRoot}",
           "requireFiles": [
             "test/**/test_helper.exs",
             "test/**/*_test.exs"

lib/live_state/channel.ex

@@ -107,7 +107,8 @@ defmodule LiveState.Channel do
             {:noreply, initialize_state(state, socket)}
 
           {:error, error} ->
-            {:error, error}
+            push_error(socket, error)
+            {:noreply, socket}
         end
       end
 
@@ -194,6 +195,14 @@ defmodule LiveState.Channel do
         push(socket, name, detail)
       end
 
+      def push_error(socket, message) when is_binary(message) do
+        push(socket, "error", %{message: message})
+      end
+
+      def push_error(socket, error) do
+        push(socket, "error", error)
+      end
+
       defp push_state_change(socket, state, version) do
         payload = %{} |> Map.put(state_key(), state) |> Map.put(state_version_key(), version)
         push(socket, "state:change", payload)

test/bad_init_channel_test.exs

@@ -0,0 +1,30 @@
+defmodule LiveState.LiveStateChannelTest do
+  use ExUnit.Case
+
+  import Phoenix.ChannelTest
+  alias LiveState.Test.BadInitChannel
+  alias LiveState.Test.UserSocket
+
+  import LiveState.TestHelpers
+
+  @endpoint LiveState.Test.Endpoint
+
+  setup do
+    start_supervised(@endpoint)
+    start_supervised(Phoenix.PubSub.child_spec(name: LiveState.Test.PubSub))
+
+    {:ok, _, socket} =
+      socket(UserSocket, "wut", %{})
+      |> subscribe_and_join(BadInitChannel, "wutever", %{})
+
+    {:ok, %{socket: socket}}
+  end
+
+  test "init" do
+    assert_push(
+      "error",
+      %{message: "you stink"}
+    )
+  end
+
+end

test/support/bad_init_channel.ex

@@ -0,0 +1,10 @@
+defmodule LiveState.Test.BadInitChannel do
+  @moduledoc false
+
+  use LiveState.Channel, web_module: LiveState.Test.Web
+
+  def init(_channel, _params, _socket) do
+    {:error, "you stink"}
+  end
+
+end