Jump.CredoChecks.LiveViewPubSubRequiresConnected (Jump.CredoChecks v0.5.0)

Basics

This check has a base priority of high and works with any version of Elixir.

Explanation

LiveView mount/3 runs twice: once for the disconnected static render and once when the WebSocket connects. Phoenix.PubSub subscriptions in the disconnected mount attach to a process that is about to die, so they should only run when the socket is connected.

# ❌ Bad — subscribes during the disconnected mount *and* after the WebSocket connects
def mount(_params, _session, socket) do
  PubSub.subscribe("my-topic")
  {:ok, socket}
end

# ✅ Good — only subscribes once the LiveView is connected
def mount(_params, _session, socket) do
  if connected?(socket) do
    PubSub.subscribe("my-topic")
  end

  {:ok, socket}
end

Check-Specific Parameters

Use the following parameters to configure this check:

:custom_pubsub_functions

Additional functions that wrap Phoenix.PubSub.subscribe/{2,3}. Each entry is {module, function} for qualified calls, {function, arity} for local/imported calls, or {module, function, arity} to also constrain arity.

Example:

  {Jump.CredoChecks.LiveViewPubSubRequiresConnected,
   custom_pubsub_functions: [
     {MyAppWeb.PubSub, :subscribe},
     {:subscribe_user_events, 1}
   ]}

...would match:

  MyAppWeb.PubSub.subscribe("topic")
  subscribe_user_events(socket)

This parameter defaults to [].

General Parameters

Like with all checks, general params can be applied.

Parameters can be configured via the .credo.exs config file.