Linter Rule: Prefer link_to over a manual <a> tag with an ERB href

Rule: actionview-prefer-link-to-helper

Description

Reports an <a> tag whose href is a single ERB output tag, and reports the link_to call that replaces it, with the link's other attributes carried across as options.

When the link's content is one piece of text, or one output tag holding an expression that can move into an argument list, the replacement uses the text argument:

<a href="<%= user_path(@user) %>" class="btn" data-turbo-method="delete">Profile</a>
Prefer the `link_to` helper over a manual `<a>` tag with an ERB `href`. Write `<%= link_to "Profile", user_path(@user), class: "btn", data: { turbo_method: "delete" } %>` instead, which is the Action View API for links and keeps the URL and the link's attributes in one Ruby call. (actionview-prefer-link-to-helper)

Anything else reports the block form, which leaves the content exactly where it is:

<a href="<%= post_path(@post) %>">
Prefer the `link_to` helper over a manual `<a>` tag with an ERB `href`. Write `<%= link_to post_path(@post) do %>` with the link's content in the block instead, which is the Action View API for links and keeps the URL and the link's attributes in one Ruby call. (actionview-prefer-link-to-helper)
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</a>

Rationale

link_to is the Action View API for links. It runs the URL through url_for, so the same call accepts a route helper, a plain String, a model, an array, or an options Hash, and it builds the rest of the tag from a Ruby Hash, so classes, data: options and conditional attributes are expressed as Ruby rather than as interpolation inside markup.

The rule does not care whether the expression is a route helper. url_for returns a String unchanged, so link_to "Docs", @external_url renders exactly what <a href="<%= @external_url %>">Docs</a> renders, and the same holds for a helper of your own, a local variable, or an interpolated String. What the rule keys on is that the href is computed at all, which is the point where link_to starts paying for itself.

A link whose href is a literal, a fragment, or an external URL is left alone.

What is left alone

• An href that holds more than the expression, since "<%= root_path %>#section" needs the fragment folded into the argument before link_to can express it.
• An expression carrying its own control flow, such as <%= @event.url if @event.published? %>, since a modifier if binds to the whole link_to call once it is moved into an argument list.

Autofix

This rule is autocorrectable. The fix replaces the whole element, so it only runs when every attribute converts exactly. Roughly one offense in eight is reported without a fix, because one of these applies:

• A value that cannot go into a double quoted Ruby string as written, because it contains ", \, #, or an & that may start an entity reference.
• An attribute with no value, such as download. download: true renders download="true", which names the downloaded file rather than leaving it to the browser.
• An attribute name that is not a Ruby key, such as Alpine's @click, or a name built from ERB.
• An attribute repeated on the same tag, which resolves to the first one in HTML and to the last one in a Ruby Hash.
• An ERB tag sitting between the attributes rather than inside one.

In those cases the message still reports the link_to call for the URL and the content, and says that the remaining attributes have to move by hand.

Where a call was written without parentheses, both the message and the fix put them back, since link_to image_tag "logo.svg", alt: "Home", root_path is a syntax error and link_to url_for action: :index do would hand the block to url_for.

Examples

✅ Good

<%= link_to "Dashboard", dashboard_path %>

<%= link_to user_path(@user), class: "btn" do %>
  Profile
<% end %>

<a href="https://example.com">Example</a>

<a href="#main">Skip to content</a>

🚫 Bad

<a href="<%= dashboard_path %>">Dashboard</a>
Prefer the `link_to` helper over a manual `<a>` tag with an ERB `href`. Write `<%= link_to "Dashboard", dashboard_path %>` instead, which is the Action View API for links and keeps the URL and the link's attributes in one Ruby call. (actionview-prefer-link-to-helper)

<a href="<%= user_path(@user) %>" class="btn">Profile</a>
Prefer the `link_to` helper over a manual `<a>` tag with an ERB `href`. Write `<%= link_to "Profile", user_path(@user), class: "btn" %>` instead, which is the Action View API for links and keeps the URL and the link's attributes in one Ruby call. (actionview-prefer-link-to-helper)

<a href="<%= @external_url %>">Docs</a>
Prefer the `link_to` helper over a manual `<a>` tag with an ERB `href`. Write `<%= link_to "Docs", @external_url %>` instead, which is the Action View API for links and keeps the URL and the link's attributes in one Ruby call. (actionview-prefer-link-to-helper)

<a href="<%= url_for(@post) %>"><%= @post.title %></a>
Prefer the `link_to` helper over a manual `<a>` tag with an ERB `href`. Write `<%= link_to @post.title, url_for(@post) %>` instead, which is the Action View API for links and keeps the URL and the link's attributes in one Ruby call. (actionview-prefer-link-to-helper)

Configuration

This rule only applies to Action View projects, so it needs framework to be set:

framework: actionview

References

• ActionView::Helpers::UrlHelper#link_to