Linter Rule: Only allow strict local definitions in partial files

Rule: actionview-strict-locals-partial-only

Default: Disabled (opt-in)

Description

Detects strict locals declarations in templates that are not Rails partials. A partial is any template whose filename begins with an underscore, such as _card.html.erb.

Rationale

Action View applies strict locals to every template, so a declaration in a view or a layout is honored. The question this rule answers is whether such a template should take locals at all.

A controller renders its view with no locals, so a required local is only reachable when every action rendering that template passes locals: explicitly. Instance variables assigned in the action are the usual way to hand data to a view, and they keep working alongside a declaration, since strict locals only constrain the locals hash.

Layouts have a second reason to avoid locals. Action View passes one locals hash to both the layout and the template it wraps, so a layout that accepts no locals raises ActionView::StrictLocalsError as soon as any template using it is rendered with locals. A layout that needs to tolerate them declares <%# locals: (**) %>.

Examples

✅ Good

app/views/users/_card.html.erb

<%# locals: (user:) %>

<div class="user-card">
  <%= user.name %>
</div>

app/views/users/show.html.erb

<div class="user-card">
  <%= @user.name %>
</div>

🚫 Bad

app/views/users/show.html.erb

<%# locals: (user:) %>

<div class="user-card">
  <%= user.name %>
</div>

Configuration

Strict locals is an Action View feature, so this rule only applies to Action View projects and needs framework to be set:

framework: actionview

This rule is disabled by default. To enable it, add to your .herb.yml:

.herb.yml

linter:
  rules:
    actionview-strict-locals-partial-only:
      enabled: true

References

• Action View - Strict Locals