Basics

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

Explanation

Prefers the :for={item <- @collection} attribute directly on an element over a <%= for ... do %> EEx block when the block wraps a single element.

When the loop body is just one element, <el :for={...}> reads cleaner and keeps the iteration attached to the element being repeated. Reserve <%= for %> for loops that genuinely need to emit two or more sibling elements per iteration.

The check inspects every ~H sigil and every .heex template referenced via embed_templates. It locates each <%= for ... do %> block, scans its body for top-level HTML/HEEx elements (skipping nested EEx blocks), and flags the block when exactly one element is found.

Bad

<%= for item <- @items do %>
  <li>{item.name}</li>
<% end %>

Good

<li :for={item <- @items}>{item.name}</li>

<%= for item <- @items do %>
  <dt>{item.name}</dt>
  <dd>{item.value}</dd>
<% end %>

Check-Specific Parameters

There are no specific parameters for this check.

General Parameters

Like with all checks, general params can be applied.

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