Linter Rule: Disallow empty ERB control flow blocks

Rule: erb-no-empty-control-flow

Description

Disallow empty ERB control flow blocks such as if, elsif, else, unless, for, while, until, when, in, begin, rescue, ensure, and do blocks.

Empty control flow blocks add unnecessary noise to templates and are often the result of incomplete refactoring, copy/paste errors, or forgotten placeholder code.

Rationale

An empty control flow block serves no purpose and makes templates harder to read. It often indicates code that was accidentally deleted, an incomplete refactoring where the logic was removed but the structure was left behind, or a placeholder that was never filled in.

This rule helps keep templates clean and intentional. Offenses are reported as hints with the unnecessary diagnostic tag, so editors like VS Code will render the empty blocks with faded text.

Examples

✅ Good

<% if condition %>
  <p>Content</p>
<% end %>

<% case status %>
<% when "active" %>
  <p>Active</p>
<% when "inactive" %>
  <p>Inactive</p>
<% end %>

<% items.each do |item| %>
  <p><%= item.name %></p>
<% end %>

🚫 Bad

<% if condition %>
Empty if block: this control flow statement has no content (erb-no-empty-control-flow)
<% end %>

<% if condition %>
  <p>Content</p>
<% else %>
Empty else block: this control flow statement has no content (erb-no-empty-control-flow)
<% end %>

<% case value %>
<% when "a" %>
Empty when block: this control flow statement has no content (erb-no-empty-control-flow)
<% when "b" %>
  <p>B</p>
<% end %>

<% unless condition %>
Empty unless block: this control flow statement has no content (erb-no-empty-control-flow)
<% end %>

<% items.each do |item| %>
Empty do block: this control flow statement has no content (erb-no-empty-control-flow)
<% end %>

<% begin %>
  <p>Try this</p>
<% rescue %>
Empty rescue block: this control flow statement has no content (erb-no-empty-control-flow)
<% end %>

References

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