Soundcheck.Check.Design.UnreadAssign (soundcheck v0.1.0)

Basics

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

Explanation

Flags assign keys a LiveView or LiveComponent sets but never reads: not in its templates, not in any layout, and not through socket.assigns in its code. Every assign lives in the process and goes through change tracking for nothing.

Before:

def mount(_params, _session, socket) do
  {:ok, assign(socket, posts: list_posts(), page_size: 20)}
end

# no template or callback reads @page_size

After:

def mount(_params, _session, socket) do
  {:ok, assign(socket, posts: list_posts())}
end

Only literal keys count. When code passes the assigns map along whole (helper(socket.assigns), <.panel {assigns} />), any key could be read there, and the check skips the module. Keys read only by an on_mount hook or a parent are reported; list them in ignore_assigns.

Confidence: medium. Tier: syntactic (works without compiling).

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.

:ignore_assigns

Keys never reported (atoms).

This parameter defaults to [:page_title].

General Parameters

Like with all checks, general params can be applied.

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