Jump.CredoChecks.UnusedLiveViewAssign (Jump.CredoChecks v0.4.0)

Basics

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

Explanation

Checks for literal LiveView assigns that are written by a module but never read in that module's Elixir or HEEx source.

This check is intentionally conservative. It is a source-level Credo check, not compiler-grade dataflow analysis, so it only tracks assign usage patterns that are obvious from the current module's Elixir source and related HEEx templates.

Conventions and limitations:

• Helper functions should read the assigns map through a variable named assigns or through socket.assigns. If you bind assigns to another name (like %{assigns: opts} = socket, followed by using opts.my_attr), the reads will not be recognized as being related to LiveView assigns.
• Only literal writes via assign, assign_new, assign_async, allow_upload, stream, stream_async, and update are checked.
• Writes to dynamic assign keys are not tracked. Examples include assign(socket, field, value), socket.assigns[field], and Map.get(assigns, field).
• Phoenix.Component.assigns_to_attributes/2 is not treated as a read. Prefer explicit attr declarations and attr :rest, :global for forwarded attributes.
• Some assigns are intended to be consumed by framework or layout code outside the current LiveView module. Use ignored_assigns to allowlist those keys.

Check-Specific Parameters

Use the following parameters to configure this check:

:ignored_assigns

Assign names that should be ignored because they are consumed outside the current LiveView module, such as by layouts, hooks, parent components, child components, or framework behavior.

:page_title is always included by default.

Example:

  {Jump.CredoChecks.UnusedLiveViewAssign,
   ignored_assigns: [:active_path]}

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.