Linter Rule: Disallow partial paths that are built at runtime

Rule: actionview-no-dynamic-partial-path

Description

Detects render calls whose partial path is interpolated, concatenated, or computed, so the partial being rendered is not known until the template runs.

Rationale

A literal path says which file it renders:

<%= render partial: "users/card" %>

A computed one does not:

<%= render partial: to_grid_partial_path(content) %>
The partial name comes from a variable or method call, so it is only known at runtime. Use a literal name, or branch between literal names, and Herb can take you to it, check the locals you pass against its strict locals, and help you rename them. (actionview-no-dynamic-partial-path)

Nothing about the second call is wrong, and Rails resolves it happily. What it costs is everything that works by reading the template rather than running it.

Herb keeps an index of the partials in a project, and a literal name is what links a render to an entry in it. Given that link the language server can jump from the call to the partial and back to every caller, rename a strict local across all of those call sites at once, complete the locals a partial declares as you type them, and report a call that passes a local the partial does not declare or omits one it requires. A computed name has no entry to point at, so each of those stops at the call.

That trade is worth making in some projects and not in others. A CMS that renders a partial chosen by an editor, or a view that dispatches on a record's type, needs a computed path, and can turn the rule off. It reports at info because a computed path is a deliberate choice rather than a mistake.

Branching between literal paths keeps the set of possible partials knowable, so it is not reported:

<%= render partial: current_user.admin? ? "admin/header" : "user/header" %>

Renders that pass an object rather than a name, such as render @products, are not reported here. See actionview-no-implicit-partial.

Only output tags are reported. A render in a silent <% %> tag discards its output and is covered by actionview-no-silent-render.

Examples

✅ Good

<%= render partial: "users/card" %>

<%= render "users/card", user: @user %>

<%= render partial: current_user.admin? ? "admin/header" : "user/header" %>

🚫 Bad

<%= render partial: "users/#{user.role}" %>
The partial name is interpolated, so it is only known at runtime. Use a literal name, or branch between literal names, and Herb can take you to it, check the locals you pass against its strict locals, and help you rename them. (actionview-no-dynamic-partial-path)

<%= render "components/#{name}" %>
The partial name is interpolated, so it is only known at runtime. Use a literal name, or branch between literal names, and Herb can take you to it, check the locals you pass against its strict locals, and help you rename them. (actionview-no-dynamic-partial-path)

<%= render partial: partial_name %>
The partial name comes from a variable or method call, so it is only known at runtime. Use a literal name, or branch between literal names, and Herb can take you to it, check the locals you pass against its strict locals, and help you rename them. (actionview-no-dynamic-partial-path)

Configuration

Disable it in .herb.yml when computed partial paths are deliberate:

linter:
  rules:
    actionview-no-dynamic-partial-path:
      enabled: false

References

• Action View - Rendering partials