Linter Rule: Do not call render without rendering the result

Rule: actionview-no-silent-render

Description

Require that all render calls in ERB appear inside output tags (<%= ... %>), not control tags (<% ... %>). Otherwise, the call is evaluated but its result is silently discarded.

Rationale

Rails' render method returns HTML-safe strings meant to be included in the final response. If it's placed inside a non-output ERB tag (<% render(...) %>), the result is silently ignored. This is almost always a mistake and leads to confusion.

This rule catches these silent rendering issues and enforces that render is only used when its result is actually rendered.

Examples

✅ Good

<%= render "shared/error" %>

<%= render partial: "comment", collection: @comments %>

<%= render @product %>

Escaped ERB tags (<%% and <%%=) are ignored. They render as the literal text <%/<%= rather than being executed, so generator and scaffold templates that emit render calls into the file they generate are not flagged:

<%% cache [menu, @page] do %>
  <ul class="nav">
    <%%= render partial: menu.to_partial_path, collection: menu.children %>
  </ul>
<%% end %>

🚫 Bad

<% render "shared/error" %>
Avoid using `<% %>` with `render`. Use `<%= %>` to ensure the rendered content is output. (actionview-no-silent-render)
Avoid using `<% %>` with `render`. Use `<%= %>` to ensure the helper's output is rendered. (actionview-no-silent-helper)

<% render partial: "comment", collection: @comments %>
Avoid using `<% %>` with `render`. Use `<%= %>` to ensure the rendered content is output. (actionview-no-silent-render)
Avoid using `<% %>` with `render`. Use `<%= %>` to ensure the helper's output is rendered. (actionview-no-silent-helper)

<% render @product %>
Avoid using `<% %>` with `render`. Use `<%= %>` to ensure the rendered content is output. (actionview-no-silent-render)
Avoid using `<% %>` with `render`. Use `<%= %>` to ensure the helper's output is rendered. (actionview-no-silent-helper)

References

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