Soundcheck.Check.Warning.SubscribedWithoutHandleInfo (soundcheck v0.1.0)

Basics

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

Explanation

Flags LiveViews that subscribe to PubSub in mount/3 but define no handle_info/2 at all. The first broadcast on the topic crashes the LiveView.

Before:

def mount(_params, _session, socket) do
  if connected?(socket), do: Phoenix.PubSub.subscribe(MyApp.PubSub, "posts")
  {:ok, socket}
end

After:

def handle_info({:post_created, post}, socket),
  do: {:noreply, stream_insert(socket, :posts, post)}

Subscriptions match subscribe_functions by alias-expanded name, as in UnguardedSubscribe. A handle_info/2 injected by a use macro counts, because the check reads the compiled module; a handler attached with attach_hook/4 silences it.

Confidence: high. Tier: semantic (run mix compile before mix credo).

Check-Specific Parameters

Use the following parameters to configure this check:

:excluded_paths

Paths to skip (atoms, binaries as path segments, or regexes).

This parameter defaults to [~r/\/test\//, "test"].

:strict

Unused.

This parameter defaults to false.

:subscribe_functions

Regexes or exact names of subscribing functions, as Module.function.

This parameter defaults to [~r/^Phoenix\.PubSub\.subscribe$/, ~r/\.subscribe$/].

General Parameters

Like with all checks, general params can be applied.

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